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Aggression among men: An integrated evolutionary explanation
Aggression and Violent Behavior 47 (2019) 29–45
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Aggression among men: An integrated evolutionary explanation John Klasios
T
Toronto, Ontario, Canada
ARTICLE INFO
ABSTRACT
Keywords: Aggression Violence Evolution Evolutionary psychology Men Culture
This paper develops an integrated theoretical explanation of aggression among men, showing that much of that aggression is anchored in naturally-selected psychological adaptations—and, in the case of honor, importantly tied to cultural transmission—designed to solve the recurrent evolutionary problems of status and honor. Both of these problems are—or at least were—very crucial to the reproductive success of men. Maintaining and cultivating honor, engaging in theft, mating competition, war, and gangs are the main phenomena thereby explained in evolutionary terms. Drawing on theoretical and conceptual resources from the evolutionary sciences at large, and in particular evolutionary psychology, the explanation developed here also and importantly pulls together the psychological, developmental, cultural, and ecological dimensions of the phenomena at issue. Doing so allows the model to sketch the ways in which the psychological adaptations underlying aggression are sensitive to both external and individual contingencies and thereby open-ended and flexible. The evolutionary model developed here draws an additional strength from its ability to grapple with individual differences and evolutionarily-novel environments. Finally, the integrated explanation is also synthesized with the evolutionary genetics and heritability of aggression.
So that in the nature of man, we find three principal causes of quarrel. First, competition; secondly, diffidence; thirdly, glory. The first maketh men invade for gain; the second for safety; and the third for reputation. The first use violence, to make themselves masters of other men's persons, wives, children and cattle; the second, to defend them; the third, for trifles, as a word, a smile, a different opinion, and any other sign of undervalue, either direct in their persons or by reflection in their kindred, their friends, their nation, their profession, or their name. —Thomas Hobbes, The Leviathan, 1651 1. Introduction In this paper, I will develop an integrated theoretical explanation of aggression among men. The theory to be developed will have its foundations in evolutionary psychology and will therefore make use of its conceptual and theoretical resources. Specifically, the explanatory account will develop the view that aggression has been partly shaped by natural-selection so as to help solve the recurrent evolutionary problems of status and honor. Accordingly, the theory will attempt to explain how certain kinds of male aggression are strategically deployed in service to these two ends. Haig (2014) has argued that sound method in psychology and the behavioral sciences has, as one of its many features, a capacity and openness to engage in partial and even provisional
model building that is importantly connected to the general explanatory approach of abductive reasoning, otherwise known as inference to the best explanation. The approach taken in this paper should accordingly be seen in that same spirit. Thus, the theory developed here ought to be construed as very much open to being developed in further detail and amended where appropriate. Accordingly, there will be many places in this account that explicitly or implicitly call for further scientific work, in order to arbitrate questions and or fill in further details. So, the project pursued here is not merely one of theoretical synthesis and model building, but also an outline of how a larger research program could proceed in order to more fully develop an evolutionary-psychological understanding of aggression among men. Ultimately, it would be desirable if the explanatory model developed here were compared with other competing theories that aim to explain the same phenomena, and such that they are competitively assessed using a framework that places important emphasis on certain explanatory virtues, such as the approach generally known as inference to the best explanation (Durrant & Haig, 2001; Haig, 2014). It is important to stress that at least some aspects of the model developed here require more empirical testing. In general, and like any explanation in science, adaptationist explanations can come in varying strengths, depending on the amount, type, and quality of evidence that has accrued both in their favor and against them. One can even construe their likelihood of being correct in Bayesian terms, if one finds
E-mail address: [email protected]. https://doi.org/10.1016/j.avb.2019.02.015 Received 5 June 2018; Received in revised form 10 January 2019; Accepted 26 February 2019 Available online 13 March 2019 1359-1789/ © 2019 Elsevier Ltd. All rights reserved.
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that assessment approach fruitful. Indeed, some aspects of the model developed here should be understood as hypotheses rather than explanatory theories—including hypotheses that would be relatively difficult to test, either directly or indirectly. Although prior work aiming to develop an overarching theory of aggression—and crime more generally—has drawn from the evolutionary sciences at large (e.g., Barber, 2009a; Barnes, Boutwell, & Beaver, 2015; Boutwell et al., 2015; Buss & Shackelford, 1997; Durrant & Ward, 2015; Ferguson, 2011; Goetz, 2010; Keller, 2017; Pinker, 2011; Walsh, 2006; Walsh & Beaver, 2009; Wiebe, 2012; Wilson & Daly, 1985), there are still many possible avenues to be explored.1 Hence, the theoretical account developed here will build on prior work as well as draw on conceptual and empirical insights from evolutionary psychology that have, to my knowledge, been heretofore unexplored in the context of understanding the dimensions of male aggression related to status and honor. The main focus of the theory developed here will be on men, for reasons that will emerge throughout. A core reason for this, however, is that, all else equal, men are faced with adaptive problems that differ in some crucial ways from women (Campbell, 2013). In particular, various forms of competition between men are a core route through which men achieve reproductive fitness, although the form of this competition need not always involve direct physical aggression between men. However, in various circumstances, aggression is often a risky but adaptive strategy for attaining or retaining status or honor, both of which are important to men's evolutionary fitness (as will be shown). From a phylogenetic point of view, it may turn out, for instance, that the psychological adaptations implicated in aggressive risk-taking are found in homologous forms in other taxa. Or adaptations for risktaking might possibly have even evolved in other taxa via convergent evolution, whereby two or more lineages evolve the same trait independently of one another—as in the case, for instance, of the evolution of flight in birds and insects. Indeed, in the later discussion of war and gangs, we will see similarities emerge between humans and chimps. Phylogenetically speaking, there is reason to think that certain kinds of aggression found among men—and humans more generally—have been selected-for across a large swath of evolutionary time and thus are present in some form in other species as well. From a developmental point of view, there may also be ways in which various learning adaptations are implicated in making one prone to aggression—for instance, via processes that look similar to operant conditioning. Among primates, reproductive variance among males is linked to sexual dimorphism, and this is concordant with the fact that species with larger differences between the sexes in various traits—such as differences in average size—are also those that tend to exhibit larger skews in reproductive success among males (e.g., Archer, 2009; Puts, 2010). And like other primates, humans also exhibit sexual dimorphism, which suggests that men descend from ancestors who often engaged in risky and violent competition with one another—at least often enough, evolutionarily-speaking. Indeed, our close evolutionary relatives, chimpanzees, are also known to use aggression in ways relevant to genetic fitness (e.g., Glowacki, Wilson, & Wrangham, 2017; Wrangham & Glowacki, 2012). A key upshot of these considerations, therefore, is that men are likely to possess a corresponding psychological nature that appropriately reflects our evolutionary history of risky and violent status competition in service of reproductive fitness. In some cultures, such as the Yanomamo, the use of violence by men—particularly the homicide of other men—is closely associated with increased status and thereby reproductive fitness (Glowacki et al., 2017). Indeed, some evidence suggests that criminality is associated with
increased reproductive success, at least in some contemporary societies, and might conceivably reflect an alternative, naturally-selected strategy (e.g., Yao, Långström, Temrin, & Walum, 2014). And some Darwinian psychologists have even hypothesized the existence of a psychological adaptation functionally-specialized for planning and carrying out homicide (Duntley & Buss, 2011). 2. A science of human nature One of the virtues of evolutionary psychology is its aspiration to integrate relevant theoretical insights and empirical findings from the evolutionary sciences, natural sciences, and social sciences. One upshot of such an approach is the realization that disciplinary boundaries are often an impediment to understanding various naturalistic phenomena, particularly those that cut across different domains of scientific inquiry. To this end, I will contend that understanding violence among men should ultimately be placed on an evolutionary foundation. In modern evolutionary psychology, for instance, work has been done on both the universal aspects of the human mind and those aspects that vary between conspecifics (i.e., sex differences, individual differences). In considering the ways in which an evolutionary approach might be applied to the theory developed in this paper, we should be open-minded about how both universal and variable aspects of our evolved psychology may give rise to violence. One of the principal aims of evolutionary psychology is to develop a mature and rigorous science of human nature. And like much if not all of the natural sciences at large, one of the primary aims of evolutionary psychology, if not the primary aim, is to achieve the kind of explanatory unification which brings with it an understanding of how broader classes of phenomena are caused by underlying causal mechanisms. In particular, this would ultimately be an explanation of human cognition and behavior in terms of the mechanisms instantiated in the brain that were shaped by natural selection (viz., via blind variation of heritable traits and environmental filtration). The community of researchers pursuing this goal avail themselves of anything of relevance from branches of science such as neurobiology, cognitive science, anthropology, economics, and, of course, evolutionary biology (though this is not an exhaustive list of tributary disciplines). To begin with, I will outline a framework that has been developing in recent years within evolutionary psychology. Such a framework will (I contend) serve as a good foundation on which to formulate an explanatory account of aggression among men. 3. Evolutionary psychology: central concepts According to various evolutionary psychologists, the mind is comprised of a collection of functionally-specialized psychological adaptations (Barrett & Kurzban, 2006; Tooby & Cosmides, 2015). Psychological adaptations are biological adaptations, and biological adaptations are a widespread (Dawkins, 1986; Dennett, 1995; Williams, 2008) and, for many, very explanatorily important feature of the living world (Godfrey-Smith, 2001). And like biological adaptations more generally, each of these psychological adaptations possess an evolutionary history which shaped it—via natural selection—to perform a function (or multiple functions), roughly speaking. Although any given psychological adaptation may have been shaped gradually over extremely long periods of evolutionary time, evolutionary psychologists are often most interested in psychological adaptations—or elements of psychological adaptations—which were substantially if not mainly shaped and solidified over the last 2.5-million years, approximately speaking. It is this range of evolutionary time that evolutionary psychologists often refer to as the “Environment of Evolutionary Adaptedness” (or simply the “EEA”). Each psychological adaptation can be said to have an EEA, which, conceptually speaking, encompasses any and all of the selection pressures that were causally implicated in the shaping of the adaptation in question—and, in this sense, psychological adaptations are no
1 Some non-evolutionary explanations of crime, such as the one developed by Agnew (2016), are roughly compatible with evolutionary explanations and overlap with them to varying degrees.
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different from any other biological adaptation in the living world, as all adaptations owe their etiology to particular selective forces that have acted throughout historical time. To briefly illustrate the manner in which psychological adaptations are connected to their corresponding selective histories, we can consider disgust, which evolutionary psychologists have posited as a psychological adaptation (e.g., Tybur, Lieberman, Kurzban, & DeScioli, 2013). Concisely speaking, one of the postulated functions of disgust is to adaptively guide individuals away from substances—i.e., foods, excrement—close contact with which would not conduce to fitness—for in ingesting a poisonous food substance, say, an individual's survival and reproductive prospects might very well be interfered with, such that their fitness prospects would be better had they not ingested it. Current understanding of psychological adaptations within evolutionary psychology sees them as relatively responsive to environmental inputs of varying sorts, be they endogenous (events within the confines of the organism) or exogenous (events originating in the external physical ecology or cultural environment, etc.). A very useful way of conceptualizing the responsiveness of psychological adaptations at a relatively abstract level is to view them under the lens of the type/token distinction (Barrett, 2006). For instance—and to foreshadow an issue that will arise later—consider a psychological adaptation functionally designed to attend to honor—or, more specifically, anything pertaining to an “honor culture” and the standing of one's honor within their local social environment. In such a case, dealing with the existence of an honor culture (generally speaking), and assessing one's standing within it, would be the type of ancestral problem that the psychological adaptation evolved to solve. However, the exact details of one's particular honor—namely the reputation for honor that one actually has among their social peers at a given time—would be a token of the aforementioned type of ancestral problem. In this sense, a type description of a psychological adaptation specifies its design in relatively broad terms, whereas a token description is a more refined and detailed description of various manifestations of the psychological adaptation in view of its particular developmental history in a particular agent. Psychological adaptations are also properly seen as evolved developmental systems (as per evolutionary developmental biology), and so they each have an underlying logic which instantiates itself throughout development (Tooby, Cosmides, & Barrett, 2003). Barrett (2015) has developed a very useful understanding of psychological adaptations, according to which the type of ancestral problem for which a psychological adaptation evolved to solve is specified by its design space—its functionally-specialized, naturally-selected rationale(s). Correspondingly, the token expressions of a psychological adaptation are embodied in its phenotype space—its particular manifestation in any given individual at a given time. The functionally-specialized design space of a given psychological adaptation can also be conceptualized as inhabiting some region of an even larger design space, which can be construed as a massively multidimensional space of all hypothetically possible psychological adaptations that could arise in a biological organism. The manifestation in phenotype space of a given psychological adaptation in a given individual at a given time, on the other hand, can be conceptualized as inhabiting some region of an even larger phenotype space, which can be construed as a massively multidimensional space of all hypothetically possible phenotypic expressions that could arise in a biological organism. An adaptation's design space is intimately related to its phenotype space. Broadly speaking, an adaptation's particular design space developmentally interacts with the “environment” (viz., all causally-relevant properties and events) in particular ways, and such that a particular phenotype emerges through that interaction. So, an adaptation's design space can be conceptualized as all—or at least many—of the phenotypic expressions that have been selected-for during the evolutionary history of that adaptation. More generally, however, all of these phenotypic expressions are a subset of the larger phenotype space of all possible phenotypic expressions that might hypothetically be connected to a given adaptation. To reiterate, all of the
phenotypic expressions that have been selected-for during the evolutionary history of an adaptation constitute that adaptation's design space—thus, an adaptation's design space is equivalent to that particular subset of phenotype space. Moreover, an adaptation's design space may—and in many cases, can—give rise to phenotypic expressions that fall outside of the subset of phenotypic expressions in virtue of which that adaptation was selected-for in the evolutionary past. This is effectively the same as saying that an adaptation possesses a reaction norm which can produce a range of phenotypic expressions, and such that its phenotypic expressions depend in certain (often complex) ways on the wider developmental environment. So, the possible phenotypic expressions that can arise out of an adaptation's design space can be entirely novel vis-à-vis the phenotypic expressions that have arisen from that design space in the past lineage of an organism (during which the adaptation was selected-for). Ultimately, however, the phenotypic expressions that are actually possible expressions of an adaptation's design space are a complicated empirical issue that cannot be settled on conceptual grounds alone.2 Henceforth, I will use the term “design”, for short, to refer to an adaptation's design space. Of course, only careful empirical investigation will allow us to understand a given adaptation's design and the manner in which that design developmentally interacts with other psychological adaptations, the agent's body, and environmental variables to give rise to any of its phenotypic expressions. In order to forestall one possible objection, it should be noted that psychological adaptations can be designed to learn and process cultural information, which can accordingly interact with other psychological adaptations in the mind. Another key conceptual and methodological resource is the modeling of psychological adaptations, which in turn are instantiated in evolved developmental systems within the brain. Ultimately, understanding a psychological adaptation in a comprehensive manner would entail possessing a computational model that specifies both its cognitive specifications (e.g., Frankenhuis, Panchanathan, & Barrett, 2013) and the manner in which those specifications map onto the brain (e.g., Bechtel, 2012, 2006). Aiming for this full-blooded style of explanation is unnecessary for a fruitful understanding of psychological adaptations to be had in the interim, of course. Hence, those wishing to gain an evolutionary-psychological understanding of aggression among men need not specify the precise instantiation details of such aggression in terms of evolved developmental systems in the brain, although instantiation details—such as relevant physiological aspects—can most certainly help illuminate the “higher-level” phenomena which they ultimately instantiate, namely cognitive processes (e.g., Platek, Keenan, & Shackelford, 2007; Platek & Shackelford, 2009). Rather, for many purposes, it will be sufficient to develop computational models of the various functionally-specialized psychological adaptations that govern aggression among men. It is beyond the scope of the present paper to explore the manner in which the brain is computational. Those interested in fuller treatments of this topic may wish to consult Marcus (2003) and Gallistel and King (2011). Roughly speaking, computational models of psychological adaptations aim to specify their representations and algorithms, as well as the manner in which those adaptations interact both with the wider environment and the rest of the mind and body. Computational models of psychological adaptations, therefore, permit for scientifically rigorous explanations that integrate the highly complex matrix of cognition, development, and ecology (the latter of which also includes the cultural sphere). In addition to being integrative, an evolutionary-psychological approach allows researchers to aim at carving the mind's nature at its proverbial ontological joints, which is tantamount to providing a schematic of all of the mind's
2 Barrett (2015) provides a comprehensive and in-depth explanation of these issues. This style of abstract scientific modeling is indeed found throughout much of science. A clear and thorough analysis of such abstract and or idealized models is given by Chakravartty (2007, 2010).
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component psychological adaptations. For our purposes, this means computationally modeling the developmental design of the psychological adaptations that underlie aggression among men, including the specific manner in which those psychological adaptations are designed to interact with the wider ecology. Because adaptations are always shaped by past selection processes, understanding their designs will also illuminate if and when their development and operation is dysfunctional—that is to say, mismatched with current environments (e.g., Kanazawa, 2004). The evolutionary-psychological account being developed in this paper, it should be underscored, aims at a “law-like” understanding of aggression between men, and one that aims to have universal scope. Finally, the claim that much about aggression between men can be understood in terms of modeling psychological adaptations absent much if any knowledge of their instantiation details in terms of neurobiology can be buttressed by recalling an episode from the history of science. Namely, one need only recall that Newton's law of universal gravitation was formulated and accepted as a (mathematical) explanation of the phenomenon even though a causal–mechanistic understanding of how gravity worked was wholly absent at the time, and remained unknown until Einsteinian relativity was established at a much later time (although the explanation of gravity provided by general relativity is not in terms of a “mechanism” per se, but rather in terms of space-time curvature). Indeed, as has been pointed out by evolutionary psychologists, discovery of the precise causal–mechanistic implementation details of psychological adaptations—that is to say, their neurobiology—can realistically only proceed once such psychological adaptations have been discovered in the first place. And this means that the manifold cognitive and behavioral regularities of those psychological adaptations need to first be detected and both adequately and progressively modeled in computational terms. To the extent that this is accomplished, neurobiological discovery will be more or less proportionately guided in informed and fruitful ways. Methodologically speaking, Schmitt and Pilcher (2004) and Andrews, Gangestad, and Matthews (2002) provide discussions of how empirical investigators can identify psychological adaptations, interpret their functional rationales, and understand their design features and the ways in which those adaptations develop.
Malamuth, Huppin, & Paul, 2005). Accordingly, one might wish to model the underlying psychological adaptation(s) that might govern such phenomena. To this end, various sorts of questions might be posed, such as what individual traits, in both the perpetrator and the victim, and what kinds of external conditions, might increase (or decrease) the likelihood of the hypothetical adaptation generating violence and threats of violence. It is worth underscoring that the existence of laws and punishments for such behaviors does not foreclose the possibility that there exist underlying psychological adaptations designed to give rise to violent behaviors under certain conditions. Behaviors in modern contexts that do not lead to the maximization of fitness can nonetheless arise from the proper functioning of naturally-selected adaptations, which would be analogous to a naturally-selected penchant for sugary or fatty foods leading some individuals to develop adverse health outcomes through the over-consumption of certain modern foods—such as pastries, ice cream, and French fries, etc.—even if the underlying preference was adaptive in the ancestral past, when the availability of sugar and fat was scarcer. Equally, a hypothetical psychological adaptation that contributes to modern occurrences of violence in some individuals and under certain conditions need not necessarily be fitnessmaximizing in contemporary contexts. So far as reproduction is concerned, a sexually-reproducing animal (such as a human) that persistently lacked any mating opportunities would of course fail to reproduce—although there are other ways in which it could enhance its inclusive fitness, namely by assisting the fitness of its relatives (Burnstein, 2005; Hamilton, 1964). So, we may hypothesize the existence of a psychological adaptation which becomes especially active under conditions in which an individual lacks offspring or persistently lacks mating opportunities. Accordingly, it might be hypothesized that such an adaptation leads them to be more inclined to engage in various forms of behavior, which, at least ancestrally, would have increased the probability of gaining mating opportunities. Of course, this is not to say that such a hypothetical psychological adaptation would operate in an obligate, reflexive manner; on the contrary, psychological adaptations are (or at least often are) highly sensitive to various environmental variables and to the operations of other psychological adaptions in the mind, including careful deliberation. In addition, given human sex-differences that govern obligatory parental investment in offspring (Trivers, 1972), an evolutionary perspective would also suggest the existence of important sex-differences in possible psychological adaptations that underlie the above hypothetical scenario. For instance, it is by dint of asymmetrical demands in parental investment among the sexes that we might also expect men to be more willing to utilize high-risk and even violent strategies to increase their reproductive prospects, even at the risk of serious injury or death (Wilson & Daly, 1985). Since sperm is cheap and ova are not, both sexes have evolved some key differences in mating strategies (e.g., Buss & Schmitt, 1993). Such selection pressures are widespread in the animal kingdom and fall under the general rubric of sexual selection (Andersson, 1994). Accordingly, women, on average, are choosier when selecting mating partners and will have an easier time securing a sperm donor for offspring. Correspondingly, men, on average, are less choosier when selecting mating partners and will have a relatively more difficult task securing ova to inseminate (although, of course, it should be noted that neither men nor women need consciously understand that such naturally-selected rationales underlie their cognition and behavior). So, sex differences in obligate parental investment have led women to evolve to be choosier when choosing mates, all else equal—in particular, in short-term mating contexts (cf. Miller, 2013). Hence, we might expect men to be more likely to deploy risky behaviors in various contexts, such that successful risk-taking in those contexts would tend to enhance their mating prospects. This is especially true—and importantly so—given that women are often seeking men with social status and access to valuable resources (e.g., Buss, 1989). In long-term mating contexts, such men are especially sought after by women due to the fact that such men, owing to their high social status and access to
4. Flexible designs for male aggression One initial first-pass attempt at illuminating the often complex and contingent nature of psychological adaptations is by considering them in the light of life-history theory (e.g., Kaplan & Gangestad, 2005). In its most general sense, life-history theory conceives of animal life as ultimately concerned with survival and reproduction. And it is life-history theory which highlights and attempts to understand the various tradeoffs between these two chief aims. In the case of humans, for instance, reproduction can be partitioned into mating effort and parenting effort, both of which can be traded-off with one another: an individual that decides to allocate time, resources, and energy to raising offspring at any given duration of time forsakes allocating them to the pursuit of another mating partner, and vice versa. It is important at this point to stress, once again, that the designs of psychological adaptations were all shaped by ancestral selection pressures. So, in the context of modern societies, there are no guarantees that they will operate in ways that conduce to biological fitness (viz., reproduction), either in any given individual or within a population in general. Indeed, there is no a priori guarantee that any given adaptation will even develop in a manner entirely congruent with its underlying design. Hence, it may turn out, for example, that certain types of violence were (or plausibly were) adaptive (in the biological fitness sense) in ancestral conditions, but are not (or at least not always) adaptive in modern conditions. For instance, some evolutionary psychologists have hypothesized that violence and threats of violence directed at mating partners may have evolved via natural selection because such behavior was ancestrally adaptive (at least under certain conditions, and at least in a probabilistic sense) (e.g., 32
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valuable resources, can parlay such status and resources into a woman's children, and by extension enhance her reproductive fitness (e.g., Marlowe, 2003; Von Rueden, Gurven, & Kaplan, 2010). Just as importantly, and much like many other species, men evince physical, cognitive, and behavioral features that reflect an ancestral past of at least some degree of aggressive competition with one another (Archer, 2009; Puts, 2010). Such aggressive competition between men would have been over access to women (as mating partners) or over valuable resources, including those resources that women valued in mating partners. In other words, then, men possess many traits that bear the hallmarks of sexual selection, traits which were selected, in this case, because of their adaptive benefits in competition with other men over evolutionary time (Darwin, 1871). Appreciating both the developmental and operational flexibility of psychological adaptations can also lead us to see criminology's wellknown typology of “adolescence-limited offenders” and “life-coursepersistent offenders” in a new light (Moffitt, 1993). For instance, as has been pointed out by Kanazawa and Still (2000), young men often lack some of the attributes which make men attractive long-term partners to women, such as access to resources and other traits. So it is reasonable to think that crimes committed by juvenile males may, at least in part, reflect the kinds of temporary constraints and deficiencies that they are typically beholden to at that phase of life (e.g., Ellis et al., 2012). Thus, the observed pattern of offending carried out by many adolescents may at least partially reflect the operations of some underlying psychological adaptation(s) designed to be strategically active during the phase of life—namely, adolescence—when certain individuals are often illequipped to gain status and valuable resources in a legal, non-violent manner. To put the point another way, such psychological adaptations would accordingly generate certain sorts of cognitive processes and behaviors under appropriate conditions. Such candidate psychological adaptations could profit from further investigation, particularly of the sort that aims to uncover their computational architecture. The view that risky behavior is deployed strategically so as to acquire status and resources, which are ultimately parlayed into reproductive success, is also supported by evidence that men in monogamous relationships are less prone to violence than men either not in monogamous relationships or in relationships but not monogamous (e.g., Seffrin, 2017). So, having obtained a mate and having formed a monogamous relationship with them, a man appears to have much less need and desire to engage in aggressive risk-taking, which underscores the view that aggressive risktaking in service of attaining status and acquiring resources is primarily motivated by mating success, evolutionarily-speaking. With respect to life-course-persistent offenders, one possible hypothesis is that the male mind contains a psychological adaptation for sampling one's social and physical ecology (and one's embodied capital—to be discussed later) for the purpose of assessing what strategies might be germane to fitness. Yet here it should be stressed that in speaking of strategy assessments carried out by hypothetical adaptations, we are specifically speaking of the naturally-selected rationales that would be embodied by their designs. This is, to be clear, importantly and altogether different than saying that an individual can appreciate those rationales. All that needed to occur for those adapted designs (and the genes underlying them) to have been selected-for ancestrally was for them to have increased their bearers' fitness. In terms of strategy, if the mind is by design geared to ascertain various kinds of routes to social success—with social success standing as a proxy for the kinds of status and resources that tend to lead to greater reproductive fitness—then it should be able to use various types of input for the purposes of forming a variegated array of desires, beliefs, and goals to that end. It might be hypothesized, therefore, that such adaptations are designed to generate desires, beliefs, and goals that are, relative to available alternatives, more likely to conduce to social success in one's social and physical ecology (or would have ancestrally). In forming such desires, beliefs, and goals, it might be further hypothesized that other psychological adaptations are also designed to carry out
various sorts of appraisals of one's abilities, alliance partners, and so forth—appraisals, that is, of the various sorts of resources that would have probabilistically indexed one's capacity to attain social status ancestrally, and thereby reproductive success. Both of these cognitive processes—namely, computing what options are available for attaining success, on the one hand, and computing the wherewithal one can bring to bear on trying to attain such success, on the other—can then hypothetically be compared in some manner. In such a case, an underlying psychological adaptation can then—and perhaps on an ongoing basis—appraise the likelihood that a given individual will experience social success (this topic will be discussed in more detail later). It can be reasonably hypothesized that the designs of hypothetical adaptations underlying strategic cognition and behavior are quite openended, in which case their corresponding phenotypes might potentially underlie a wide range of routes to social success in one's local culture. To sketch a brief illustration of how such adaptations might conceivably develop and operate, we might imagine a young man whose psychological adaptations lead him to perhaps gradually realize that a range of routes to social success are unlikely for him. In which case, underlying psychological adaptations might accordingly increase the likelihood of him using aggression in strategic ways. For instance, such adaptations may compute that aggressively robbing someone of jewellery would increase his perceived status among peers and prospective mates, which might cause other adaptations to mentally rehearse various action schemata that might facilitate successful theft (e.g., Carruthers, 2015). Since psychological adaptations can be highly interconnected with one another, they can impinge on each other's computational operations, and in an iterative and complex, non-linear manner—in other words, they can feature in cycles of cognitive activity. For example, a psychological adaptation in men that computes one's ability to leverage their physicality in conflicts of interest (Sell, Tooby, & Cosmides, 2009)—by, among other things, assessing their own upper-body strength—could accordingly increase or decrease the likelihood of carrying out an assault, say, or (in keeping with the above example) attempting a violent theft. Another interesting question that can be posed in the context of an adaptationist understanding of aggression is whether men possess a psychological adaptation functionally-specialized for dealing with weapons. For instance, should such an adaptation exist, it may regulate, in part, when men use aggression (e.g., in which contexts) and how they respond to others either displaying weapons, known to possess them, or suspected of possessing them. The extent to which aggressive behavior might be learned from others should also be given consideration (e.g., Bandura, 1978; Mummendey, 1978). For instance, one might hypothesize that certain individuals who find themselves relatively disadvantaged—and therefore, from a Darwinian point of view, at a relative fitness disadvantage—might be more likely to pay close attention to others who act aggressively—and or feel motivated to seek out others with a reputation for toughness and aggression. To the extent that this may be true, individuals could attempt to learn how to think and act aggressively by observing and talking with other aggressive individuals (i.e., in order to imitate their aggression). It is also possible that aggressive behavior could be reinforced to the extent that it provides the individual with positive feedback. Wright (2017), for instance, offers a lucid discussion of how psychological adaptations can process events that are objectively harmful to one's fitness prospects as if they are actually beneficial to one's fitness prospects. For instance—and to use an example discussed by Wright—frequently consuming a large number of jelly donuts covered with powdered sugar appears to reliably get registered by one psychological adaptation or another as if one has consumed fruit, which we can assume was a healthy and fitness-conducing action in ancestral conditions. In so doing, the underlying psychological adaptation typically produces a positive affective response—that is to say, eating such donuts causes many people to feel good (at least those who like them or who have a predilection for sweet foods). Such feelings, produced by 33
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adaptations, tend to make people more likely to act in much the same way in the future. Yet, presumably the underlying adaptation registering the consumption of jelly donuts covered in powdered sugar as a boon to one's fitness prospects would continue to do so even if, objectively speaking—and perhaps also unbeknownst to the individual—eating them was actually making them less healthy, or putting them on a trajectory likely to lead to some kind of health complication later on. So, roughly speaking, psychological adaptations can sometimes register feedback as if it were a good thing—viz., as if it were beneficial to one's evolutionary fitness prospects—even when, in actuality—and particularly in a modern environment—it is harmful to one's evolutionary fitness prospects. And such a mismatch is, as noted, still likely to cause psychological adaptations to produce positive affective responses, which in turn make the behavior in question more likely in the future. Thus, to the extent that aggression receives positive feedback, it might make desisting from aggression even more difficult, at least in some individuals. This would be true even if aggression decreases one's actual fitness prospects in the current environment, and even if aggression is actually not in the interests of one's own wellbeing.
environment, should one exist. Roughly speaking, in social environments with an honor culture present, the psychological adaptation designed for reputation management develops and operates so as to be sensitive to the appropriate violations and slights to one's honor. To briefly illustrate the underlying logic of honor, we can consider a particular individual residing in a society or rural environment lacking the aforementioned institutional guards, and who also possesses a reputation for being extremely tough, belligerent, and willing to violently avenge transgressions and slights—such as theft attempts and verbal acts of disrespect. In which case—and all else equal—it would be expected that this particular individual would be less likely to be targeted in such a manner by other individuals, particularly other men, owing to their reputation for violent retribution. In addition, the honor of a man can affect his value both as a potential mate and alliance partner, with tarnished honor serving as an indicator of lower status and deficiencies in the various abilities valued in potential mates and allies, among other things. Furthermore, in anarchic-like conditions, we might expect there to be incentives to eagerly pounce on or otherwise manufacture opportunities to demonstrate and thereby broadcast a reputation for being tough, given its currency in such an environment. Ergo, it is possible that men possess a psychological adaptation for strategically utilizing violence in such an opportunistic manner (Winegard, Winegard, & Geary, 2014). For instance, according to the “Crazy Bastard Hypothesis”, men sometimes engage in behaviors that can serve to broadcast their toughness, or at least a reputation for being tough (Fessler, Tiokhin, Holbrook, Gervais, & Snyder, 2014). Finally, there is empirical evidence that honor cultures are at least partly sustained by cultural transmission occurring across generations—that is, from one generation to the next (e.g., Latzer, 2018). For example, one study found that professional hockey players raised in Canada were more likely to defend their honor by acting more aggressively during games (measured by penalty minutes) if they had been raised in towns that historically had been relatively distant from law enforcement officials (Restrepo, 2015). A natural explanation for why such players had elevated rates of aggression is that, historically, those born in such towns needed to rely more on defending their honor, since law enforcement was either less reliable or unavailable, owing to their relatively distant location in relation to those towns. Since the underlying psychological adaptation that governs honor culture and its associated aggressive tendencies served the function of increasing fitness in certain anarchic-like ancestral conditions, such an adaptation is likely to develop and operate whenever individuals find themselves in such conditions. However, given that such a psychological adaptation at least party relies on cultural transmission across generations as an important input, it appears that honor cultures can persist over time even long after they are no longer required (and no longer fitnessconducing). Thus, in the study of professional hockey players born in towns historically situated in places remote from law enforcement and courts, we can thereby explain why an honor culture has persisted among them, even though they were raised in such towns during a time when law enforcement and courts were present and reliable. For completeness, it should also be noted that processes of cultural transmission must ultimately be facilitated by underlying psychological adaptations as well (e.g., Sterelny, 2012). More generally, much empirical work remains to be done in order to illuminate all of the various functionally-specialized psychological adaptations that underlie various channels of cultural transmission and how those adaptations interface with other psychological adaptations in the mind (e.g., Tooby, 2014). It is also quite possible that those who are competitively disadvantaged and thus perceive poor prospects for social success will tend to be more likely to be receptive to honor cultures in the first place. Hence, this could explain differences between individuals living in the same locale, some of which find themselves embracing an honor culture, while others opt to eschew it (or find it less appealing, relatively speaking). In terms of the evolution of honor cultures, it may be helpful to think of culture as comprised of units of information—“memes”—that
5. Violence via honor A central motivator of violence across cultures is honor (Cohen, Nisbett, Bowdle, & Schwarz, 1996). Both empirical evidence and “agent-based” modeling show that honor is an evolutionary phenomenon that provides a fitness advantage to individuals (or would have done so under ancestral conditions), in that cultures of honor emerge in environments lacking the institutional guards that would otherwise provide safety from exploitation (Linquist, 2016; Nowak, Gelfand, Borkowski, Cohen, & Hernandez, 2016; Shackelford, 2005). So, from an evolutionary point of view, humans appear to possess a psychological adaptation for cultivating and defending their honor within particular ecological and cultural contexts, as well as for appraising the honor of others. Fundamentally, the honor of an individual can deter exploitation, and it is one's reputation for toughness which serves as the primary vehicle for communicating such information. Specifically, honor cultures are typically found in environments either lacking or deficient in policing—or some other adequate mechanism(s) by which individuals can be monitored—and where a form of dispute resolution (i.e., a justice system) is absent, unreliable, or otherwise corrupt. It is precisely under such conditions that individuals cannot rely on impartial third-parties to provide safety from and retribution for exploitation and physical harm. Indeed, under such conditions, impartial third-parties are either largely or entirely absent. Hence, absent these countervailing institutions and social arrangements, it becomes rational to cultivate and defend a reputation for being defiant in the face of infringements such as physical attacks, theft, or even verbal insults, etc.—in other words, it becomes rational to develop and guard one's honor. Indeed, even threats of such infringements can be sufficient grounds to elicit a defense of one's honor, whether by getting angered at the offending party and or violently attacking them. At root, within honor cultures, and all else equal, an individual will feel motivated to avenge any act that infringes upon their honor by responding angrily towards the perpetrator or attacking them outright—and particularly if the act and the retaliatory response are witnessed by observers, as witnesses also provide the retaliator with an audience with which to broadcast a message to (namely that the retaliator should not be exploited, derided, or otherwise slighted). So, defense of honor can indeed entail violent retribution directed at those infringing one's honor, which is often other men. This motive to avenge slights—which is underpinned by the appropriate psychological adaptation—is rational from the point of view of evolutionary fitness, since it acts as the proximate means by which one's honor is maintained. Shackelford (2005) has postulated the existence of a psychological adaptation designed for solving the problem of reputation management, which we can further postulate interfaces with an honor culture in one's social 34
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can evolve in the way that genes do. For our purposes, insofar as we're focusing on the adaptive nature of honor cultures, we can understand the units of information that comprise honor cultures as being selectedfor in environmental contexts within which they provided a fitness benefit (statistically speaking). Furthermore, defending one's honor can—and, at least ancestrally, likely regularly did—enhance one's inclusive fitness. For instance, to the degree that honor helped to safeguard one's resources and or increased their access to resources, a man's kin is also likely to benefit as a result; and any fitness benefits accrued by one's kin can count towards increasing one's inclusive fitness.
there are psychological adaptations determining the extent to which one is competitively advantaged or disadvantaged among one's peer group along the two broad domains of need and ability. For example, in societies with bridewealth and polygyny, men without mates (especially younger men) appear more likely to strategically use aggression to better their chances at attracting a mate (e.g., Hudson & Matfess, 2017), which can include participating in wars (to be discussed later). “Young bachelors who cannot afford to marry also make easy recruits for rebel armies. If they fight, they can loot, and with loot, they can wed” (M.B., 2018, para. 3). This observation is congruent with the view that certain men, owing to their disadvantaged relative-state—in this context, absent a mate and not well positioned to acquire one—will be more prone to behave in risky, aggressive ways. As such, proneness to risky aggression will flow from a relative disadvantage in both need and ability—namely, the absence of a mate and poor prospects for acquiring one, given the circumstances. Furthermore, we may hypothesize, for example, that needs for various markers of status, such as valuable objects, may be generated by an underlying psychological adaptation in relation to some appropriately circumscribed peer group. Such markers of status, should they be acquired, would help increase one's status, thus making them more appealing as alliance partners and, at least among men, more attractive to women (at least as long-term partners), especially relative to rivals. In contemporary societies, for example, luxury consumer items that effectively act as markers of status could hypothetically engender violent or non-violent theft among men whose underlying psychological adaptation appraises them as being competitively disadvantaged in relation to rivals who possess luxury consumer items. Plausibly, men who contemplate or engage in such theft might be driven to do so by underlying psychological adaptations that have computed their ability to obtain such markers of status in non-aggressive ways as, say, too difficult if not unlikely (to be discussed later). Underlying psychological adaptations might further compute an individual's ability to facilitate aggressive theft of valuable items as enhanced in some way, owing to relative advantages, or the surpassing of a certain threshold, in traits such as strength, endurance, and so forth. Since they can serve as a reliable signal of various qualities held by their possessor, the display or consumption of luxury goods can also be used to elevate one's status over others. In evolutionary biology, costly signaling occurs whenever an animal broadcasts a signal that is a reliable indicator of some underlying quality. For instance, if the intensity of a birdsong is reliably correlated with overall health because only those in very good health can produce intense birdsongs, then quality of birdsong can hypothetically serve as a reliable indicator of overall health. So, because only healthy animals can afford to produce such displays, those displays are therefore “costly signals” of that quality (in this case, health)—and costly signals are ipso facto reliable due their costs (Zahavi & Zahavi, 1999). Correspondingly, conspecifics can evolve a capacity to assess signals for properties such as reliability and quality. From a Darwinian point-of-view, luxury goods can give rise to competitive runaway processes, whereby individuals attempt to one-up each other in an iterated fashion (Frank, 2001; Miller, 2009). Hypothetically, then, men might be expected to be more prone to theft whenever such men lack the ability to acquire such luxury goods in a legal, non-aggressive manner, and so as to keep pace with rivals on that score, or to get ahead of them. In the mating domain, luxury goods might also serve as costly signals of the possessor's underlying qualities. For instance, luxury goods might serve as indicators of the financial status of the possessor, and or their general wherewithal to secure resources. Hence, potential mates might thereby assess a man's capacity to provision via his display of luxury goods. In addition, luxury goods might also hypothetically function to broadcast one's value as a potential ally if they are reliably correlated with traits and or properties that make one a valuable ally—for instance, if the possession of such
6. Relative-state, theft, and aggression Mishra, Barclay, and Sparks (2017) have developed an empirically supported, comprehensive framework for understanding the dynamics of risk-taking, which can serve as an evolutionarily-informed component of a Darwinian approach to explaining theft and gang membership (the latter of which will be discussed later). According to the “relativestate model” developed by Mishra et al. (2017), there are two pathways to risk-taking in general: one based on ability, and the other based on need. The ability-based pathway, to a first-approximation, reflects one's skills, talents, support from kin and alliances, monetary and material resources, and so forth. The ability-based pathway, moreover, can include features of one's somatic condition, such as health. The needbased pathway, to a first-approximation, reflects the various needs that an individual may appraise themselves as having, such as food, valuable objects, or mating partners (among many other possible needs). Fundamentally, one's relative-state is fundamentally a comparative issue: namely, the manner in which one compares to others in terms of abilities and needs. For instance, one's social competitors may possess status or access to valuable resources that one lacks, or one's social competitors may possess certain abilities that leave one comparatively disadvantaged. We may provisionally postulate that the relative-state model of risktaking captures the fundamental logic of whatever the psychological adaptations are that actually govern risk-taking among individuals. One benefit of having such a model is that it can serve as a useful research heuristic for identifying whatever the underlying adaptations are and mapping out their various design features—including which sorts of cognitive, bodily, and ecological variables they are sensitive to. In terms of needs, we may presume, for Darwinian reasons, that the mind contains psychological adaptations designed to deal with core needs such as acquiring food and obtaining a mate. However, given the open-endedness of many psychological adaptations and their complex interaction with one another, there will be various instrumental needs that get generated in service to core Darwinian needs. Furthermore, we should expect the range of possible instrumental needs to be very large and generated according to the designs of the appropriate psychological adaptations underlying them. According to the relative-state model (Mishra et al., 2017), risktaking is sensitive to the needs of particular individuals relative to others—for example, how an individual's access to a particular valuable resource compares to another person's access to that same resource. Relative to other individuals, the greater the disadvantage that one has in satisfying certain needs—viz., the more disadvantaged one's relative state is—the greater the likelihood that one will take risks. Risk-taking, furthermore, is also sensitive to the relative abilities of particular individuals. In the realm of needs, a Darwinian approach would suggest that the needs of men are partly shaped with reference to one's local peers, who ancestrally would have comprised one's reproductive rivals and potential allies. Thus, it would be worthwhile to better understand the psychological adaptations that compute (or the singular psychological adaptation that computes) who gets registered as one's reproductive rivals and who gets registered as one's potential allies (including how the two might overlap). Likewise, we may hypothesize that 35
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goods is correlated with valuable skills or knowledge (Plourde, 2008), social status, or traits such as strength.3 It is worth noting that evolutionary novelties such as money and luxury cars function as token representations instantiated in the phenotype of the psychological adaptation tasked with assessing which objects in one's ecology are valued and status-enhancing. A key upshot for our purposes, however, is that there are good reasons to expect there to be an underlying psychological adaptation that increases the likelihood that certain individuals—especially certain men—will, under certain conditions, engage in theft to obtain such markers of status. Other Darwinians have discussed the reasons why men have evolved a psychology that regulates risk-taking in a way that is sensitive to reproductive competition and one's standing in relation to peers in a number of crucial fitness-relevant domains (e.g., Daly, 2001; Mishra et al., 2017). It may also turn out that a low absolute level of abilities might suffice to explain why some individuals engage in aggressive theft. In such a case, we might expect underlying psychological adaptations to register a very low absolute level of abilities, which might be interpreted by the adaptation as a sign that low-risk strategies are—or were, ancestrally—unlikely to pay off in terms of social success. Accordingly, the psychological adaptation might increase the likelihood that the individual will engage in some form(s) of risk-taking, including theft. As an empirical hypothesis, therefore, it is worth testing whether chronic failure at achieving forms of social success in a legal manner is often sufficient to cause or increase the likelihood of theft, whether violent or non-violent. Such an investigation can also aim at ascertaining what cues the underlying psychological adaptation uses to compute chronic failure at achieving forms of social success in a legal manner—and whether there are specific thresholds, or whether the probability of such behavior is regulated in a way proportionate to the level and or frequency of failure. Similarly, it is also worth testing whether certain types of embodied and ecological parameters are attended to by underlying psychological adaptations as bellwethers of how likely nonaggressive strategies will garner social success for a particular individual. In which case, perhaps such parameters can be used as input into such adaptations for the purposes of impelling individuals towards more riskier, violence-prone social strategies. As per the risk-taking framework developed by Mishra et al. (2017), risk should be construed in a domain-specific rather than domaingeneral way (even though, among some individuals, it is often the case that risk-taking across various domains is correlated to some extent, and for reasons that the model can elegantly explain). Accordingly, risktaking is better viewed as arising not from a generalized propensity for risk, but rather as arising in a more specific manner, with individuals adjusting their risk-taking proclivities from domain-to-domain.4 For example, in domains where successful competition hinges heavily on strength, assessing that one is physically stronger than rivals would accordingly increase the likelihood that they would take risks in those domains, all else equal. For being stronger than one's rivals augurs well for being successful in those very domains (viz., where strength is an important factor for success). Hence, we may predict that men who are physically weaker will be less likely to engage in violent crimes, such as violent theft, whose successful execution depends in some substantial degree on physical strength, all else equal. Of relevance to this issue,
there is evidence of a psychological adaptation designed to compute an individual's strength (Sell, Tooby, & Cosmides, 2009) as well as the strength of others (Sell et al., 2009). Such assessments, therefore, can be used by other psychological adaptations implicated in computing the extent to which one should be disposed to deploying physical violence against certain individuals, in certain contexts. Equally, however, it is quite possible that possession of a weapon (and whether a potential target ostensibly possesses a weapon or is suspected of possessing one) can alter the computations of whatever the relevant psychological adaptations are that are implicated in aggressive theft, such that even relatively weak men will find aggressive theft to be a valuable option under such conditions (Fessler, Holbrook, & Snyder, 2012). Because ancestral humans probably generally gained reproductive fitness benefits from increased status (e.g., von Rueden et al., 2010; von Rueden & Jaeggi, 2016), it stands to reason that individuals—and men, in particular—would have evolved a psychological adaptation that allowed them to increase their status and or keep ahead of competitors via strategic risk-taking. Indeed, Ermer, Cosmides, and Tooby (2008) suggest the existence of a psychological adaptation that leads to riskybehavior among men in a functionally-specialized and context-sensitive manner. Specifically, and in line with their Darwinian-derived hypotheses, Ermer et al. (2008) found that men, but not women, are more likely to engage in risk-taking aimed at recouping a loss of resources—but not after gaining resources or after a loss of resources irrelevant to competition between men—and only when other men of equivalent status were observing them. These results suggest that the psychological adaptation governing risk-tasking in men is sensitive to status cues—specifically, cues that men of equal status are observing oneself. Such empirical results underscore men's sensitivity to relativestatus and lend support to the hypothesis that they have evolved an underlying psychological adaptation designed to be aware of one's relative-status and to deal with this reality in a fitness-conducing way. Indeed, such findings might lend credence to the earlier contention that violent risk-taking among men in service of acquiring luxury goods is closely connected to appraisals of relative status among reproductive competitors. In sum, aggressive risk-taking appears to be governed by underlying psychological adaptations sensitive to the ways in which one's needs and abilities compare to a reference class comprised by one's peers. Accordingly, some types of aggressive risk-taking might be explained by dint of individuals experiencing pressing needs, such as hunger, a need to maintain one's status among equal-status peers, or perhaps even sex, while other types of aggressive risk-taking will be more straightforwardly explained as a function of deficiencies or advantages in abilities, relative to some suitably circumscribed reference class of peers (Mishra et al., 2017). Fundamentally, however, it is plausible that much if not most aggressive risk-taking will occur among men for whom underlying psychological adaptations appraise as possessing abilities that make legal, non-violent routes to social success less likely if not effectively foreclosed—although, as will be discussed later, such appraisals need not be objectively accurate, as there is scope for error, especially in evolutionarily-novel environments. 7. Sex-ratios and predictive adaptive responses Another factor which may be significant for understanding aggression among men is sex-ratios, which at the very least appear to be correlated with violence (e.g., Barber, 2009b). However, even with respect to the correlation between sex-ratios and violence, some caveats are in order. Firstly, although it is often the case that an overabundance of males relative to females is often correlated with elevated rates of competitive risk-taking among males of various species, it appears as if the reverse is the case in humans (Schacht, Rauch, & Mulder, 2014; Schacht, Tharp, & Smith, 2016). In particular, an excess of women relative to men in a particular location is associated with elevated rates of violence among men. One interpretation of this pattern is that, when
3
In a related vein, Gambetta (2011) details the various ways in which signaling processes help facilitate organized crime. 4 It is worth pointing out that, in addition to helping to explain violent crimes, the framework of Mishra et al. (2017) can also help to explain “white collar” crime and non-criminal (or non-violent) forms of risk-taking, such as gambling and rock climbing. Although it might prima facie seem as if white collar crime is a maladaptive, unwise, and unnecessary form of risk-taking, its underlying rationale might make more sense when seen as a form of risk-taking stemming from the relative advantages of certain individuals, which in turn increases the likelihood of success at specific risky endeavors. 36
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women are the abundant sex, men stand to potentially benefit, from a fitness point-of-view, if they can secure more mating partners or mating opportunities via a more promiscuous mating strategy. Hence, under such a scenario, men appear to engage in more competition with one another, which could very well be tied to direct competition for mating opportunities with women (e.g., Griskevicius et al., 2009). Such competition might at least sometimes be used by women as a criterion for selecting short-term mating partners under conditions where they are the more abundant sex in a locale, or such competition between men might alternatively be used to neutralize the mating opportunities of rivals—which could thereby give competitively triumphant men better prospects for successfully courting mates (e.g., Puts, 2010). If deployed at least partially as a mate selection criterion, then, it is possible that women monitor aggressive competition between men and use it as an indicator of men's genotypic and or phenotypic quality (Gangestad, Simpson, Cousins, Garver-Apgar, & Christensen, 2004)—and or as an indicator of men's capacity to acquire resources (which would prove valuable should a woman form a long-term relationship with such men). Naturally, then, under conditions where competition between men is elevated, we could expect to see rates of violence between them elevated as well, which could explain the empirical association between violence on the one hand, and sex-ratios where women outnumber men on the other. In any case, it would be useful to model how an underlying psychological adaptation tracks the relevant sex-ratio in a given locale, and how such tracking feeds into other psychological adaptations in men that govern the propensity to engage in the kinds of risktaking that can lead to violence with other men. Empirical work by Schacht et al. (2014) is germane to this issue, as is their evolutionarilyinformed conceptualization of sex-ratios in humans. Another interesting observation of relevance here, noted by Schacht et al. (2016), is the feedback loop that incarceration can have on rates of violence between men.5 Specifically, in removing some number of reproductively active men from a given locale (at least for some time frame), incarceration is one factor that acts to alter sex-ratios, and can thereby even exacerbate sex-ratios that are already female-heavy, which in turn can increase aggressive competition between men even further, leading to elevated rates of violence. Once again, this is because of the increased mating competition that increasingly female-biased sex-ratios elicit—that is to say, the imbalance of more women relative to men tends to produce more potential mating opportunities for men, which at the same time incentivizes them to be more likely to forgo long-term commitment. Cultural norms and practices can also potentially affect rates of aggression. Socially penalizing promiscuity (e.g., Baumeister & Twenge, 2002), for instance, is a cultural norm that can regulate mating and, in so doing, significantly reduce mating competition even in contexts with sex-ratios where women outnumber men. And by dint of reducing mating competition significantly, a cultural norm that socially penalizes promiscuity can indirectly reduce aggressive competition among men. In addition, it is also plausible that female-heavy sex-ratios can contribute to violence in an additional, parallel manner via lowered rates of marriage (or lowered rates of stable pair-bonds). For instance, it is possible that male offspring being reared by single parents are, all else equal, disadvantaged in various ways relative to other offspring reared by intact families (that is, families with both parents present). Accordingly, since they might leave individuals competitively disadvantaged, it is possible that such developmental environments negatively affect an individual's relative-state in some ways, which could thus serve to increase the likelihood that they will ultimately deploy aggressive risk-taking as they mature. Empirically, family disruption is associated with rates of violent crime (e.g., Messner & Sampson, 1991). However, such a causal pathway should be investigated carefully, in particular with an eye towards evaluating it with, say, methods in
behavior genetics, which can control for the possible effects of genes, as heritable factors can confound an association between family disruption and increased levels of violent crime. At any rate, there is some evidence in behavior genetics—which controls for the potential confounding of heredity—that suggests that family disruption might ultimately negatively affect the relative-state of offspring (e.g., Burt, Barnes, McGue, & Iacono, 2008). In the realm of sexual competition, the psychological adaptation that underlies men's jealousy can, under certain conditions, lead to men exacting physical revenge on the men perceived to have had sex with their partners, whether real or imagined (and, no doubt, men can also exact physical revenge on their partners, and regardless of whether an act of cuckoldry is either real or imagined) (e.g., Buss & Shackelford, 1997). Of course, exacting such revenge on other men can lead to homicide as well. There are at least two naturally-selected rationales embodied by the psychological adaptation governing such acts (Buss, 2015). One rationale is to prevent a man's partner from cuckolding him in the first place, primarily by exercising vigilance over her. A second rationale is to maintain a man's honor among peers in the event that he has either been cuckolded or merely suspected of having been—the idea here, as with honor more generally, is that when others know or merely believe that a man has been cuckolded by his partner, but where he has also not acted to restore his honor, it broadcasts a signal that the man can be taken advantage of without reprisal. Recent work on “predictive adaptive responses” may also be relevant to understanding the evolutionary psychology of aggression among men. Predictive adaptive responses are hypothesized to be responses to particular variables, either within the organism or in the external environment, which occur during development (Nettle, Frankenhuis, & Rickard, 2013). As such, their naturally-selected designs can allow for organisms to develop in ways that would be adaptively optimal (at least under ancestral conditions) given the situation they find themselves in, whether ecologically and or in terms of physical and mental condition. One possible hypothesis in relation to male aggression pertains to the way in which the psychological adaptations underlying predictive adaptive responses might provide input into the psychological adaptation governing risk-taking. Specifically, it may be that particular inputs—for instance, very poor nutrition and or poor health—could function as input that causes the underlying psychological adaptation governing risk-taking to compute one's relative-state as disadvantaged (to some degree). Similarly, Frankenhuis and Panchanathan (2011) have discussed the ways in which psychological adaptations might be designed to “sample” environments for input on how to optimally develop. 8. Putting developmental trajectories and evolutionary mismatch in computational perspective Given the overarching theoretical model being developed in this paper, the understanding of aggressive risk-taking in terms of relativestate can be complemented by generating hypotheses about some of its other developmental and computational aspects. For instance, one hypothesis might examine the manner in which traits such as general intelligence and conscientiousness are processed by the underlying psychological adaptation that computes one's relative-state over time. Accordingly, one could, for instance, devise a variety of empirical tests that aim to look at whether variations in such traits in adolescents affect their aggressive risk-taking propensities—and if so, the particular domains to which such aggressive risk-taking is directed at. Many biosocial criminologists, for instance, would likely see these sorts of hypotheses as quite plausible, as they have frequently pointed out correlations between criminal and violent phenomena on the one hand, and traits such as intelligence (and scholastic achievement) on the other (e.g., Beaver et al., 2013; Schwartz et al., 2015). Taking this at face value, it may be that an underlying psychological adaptation computes one's abilities as it gradually receives various sorts of feedback
5 Similarly, incarceration rates, in altering sex-ratios, can reduce marriage rates (e.g., Charles & Luoh, 2010).
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throughout development, via interaction with the environment. In that case, an individual's underlying psychological adaptation might compute a disadvantaged relative-state of some magnitude when it consistently registers poor performance on certain kinds of tasks, and in comparison with peers—owing substantially, in this case, to lower levels of general intelligence. Such a process might operate in the context of modern societies when individuals low in general intelligence (and or conscientiousness) experience consistent negative feedback in the form of, say, failed tests at school, low school grades, etc., and where cues of one's poor standing relative to others are registered. Hypothetically, an individual need not even necessarily be fully cognizant of any of these cues so long as an underlying psychological adaptation detects and appropriately registers them. Once computed, the magnitude of the disadvantaged relative-state will then serve to regulate the individual's aggressive risk-proneness, although the manner in which that aggressive risk-proneness gets expressed might be specific to certain domains. Of course, the exact range of cues that such an adaptation would take in as input in determining one's relative-state at a given time is an empirical question. But in general, once such a disadvantaged relative-state was computed, it would influence the way in which the individual interacted with their environment such that opportunities for aggressive risktaking would be proportionally more likely to be sought after and capitalized on, all else equal. Empirical work by other evolutionary psychologists can also dovetail on these issues. For example, stronger men (as indexed by upper-body strength) have been found to be more likely to be assertive in contexts where there are conflicts of interest (Sell, Cosmides, et al., 2009; Sell, Tooby, & Cosmides, 2009). Sell, Cosmides, et al. (2009) and Sell, Tooby, and Cosmides (2009) argued that this phenomenon is governed by a psychological adaptation that assesses one's physical prowess and uses it as an input to compute an internal regulatory variable that governs behavior such as proneness to anger and feeling entitled to having conflicts of interest solved in one's favor. It is quite conceivable that such an internal regulatory variable that indexes physical prowess could influence where and when one engages in violence—for instance, the conditions under which one aggressively steals a valuable item, or whom one physically retaliates against in order to avenge a verbal derogation. In which case, the internal regulatory variable that indexes physical prowess would be available as input into the overarching psychological adaptation that governs aggressive risk-taking. More specifically, physical prowess can potentially be used as a relative advantage within broader contexts of relative disadvantage, as when an otherwise dim, poorly educated, impulsive individual uses their above average strength to overpower others in order to aggressively steal a valuable item or win a dominance competition of some kind. Interestingly, when specific relative disadvantages and specific relative advantages are juxtaposed against one another, it may be possible to predict or explain particular developmental paths taken by such individuals. For instance, in the case of especially strong individuals lacking in education, intelligence, and self-control, among other things, we might empirically predict that such individuals will be more likely to engage in more fights and be charged for violent crimes. In that sense, this particular suite of traits might be increasing the likelihood that such individuals follow certain kinds of lifestyles, the particularities of which are shaped and constrained by the ecological and cultural environment in which those individuals are embedded. If borne out empirically, such a prediction would support the adaptationist hypothesis that such individuals, probabilistically speaking, are utilizing one relative advantage—above average strength—to further their ends within the larger context of relative disadvantage, where they lack educational credentials, intelligence, self-control, and so forth. In sum, the precise developmental and computational design of the underlying psychological adaptations hypothesized in the foregoing must of course ultimately be mapped through much careful empirical investigation. This computational and developmental view of the
psychological adaptations underlying aggressive risk-taking will reemerge in our discussion of reactive heritability. At this point, it is worth reiterating the fact that the designs of psychological adaptations have been shaped by ancestral selection pressures. So, in the case of psychological adaptations underlying aggressive risk-taking, we should expect that their designs will not perfectly reflect the environments encountered in modern societies. In which case, this kind of evolutionary “mismatch” introduces one source of possible error when it comes to the ways in which psychological adaptations develop and function. For instance, the underlying psychological adaptations governing aggressive risk-taking might often lead individuals in modern societies to engage in criminal activities even if doing so is, in an objective sense, unnecessary to achieve a satisfactory level of social success (whatever that level and kind of success might be). Accordingly, the relative-state model of risk-taking can accommodate cases where individuals are inclined towards certain kinds of aggressive risk-taking even when a more objective assessment of their relevant abilities would suggest that such risk-taking is unnecessary and or overly rash—viz., more rash than the underlying adaptation “believes” it to be, since the adaptation's design reflects ancestral rather than modern environments. For since one's abilities are ultimately represented (i.e., instantiated) by an underlying psychological adaptation, the psychological adaptation might very well erroneously appraise an individual's prospects for social success. In which case, the underlying psychological adaptation could construe things “as if” the individual's abilities left them at a disadvantage in the pursuit of social success, whether that disadvantage was in absolute terms or relative to some reference class of social competitors. The upshot to this is that since psychological adaptations merely execute their underlying developmental designs, objective assessment can certainly be a mark that they miss in practice. Incidentally, being cognizant of the fact that psychological adaptations were naturally-selected in ancestral conditions can also help to partially illuminate why novel substances such as alcohol can affect cognition in a way that increases the likelihood of aggression (e.g., Pihl & Peterson, 1995). For, presumably, such psychological adaptations did not evolve under conditions where such substances (i.e., alcohol) were available. To further expatiate on some of the foregoing issues, we might hypothesize that men possess the capacity to make conscious, cognitive discriminations pertaining to whether to engage in aggressive behavior, desist from it, or avoid it altogether. For instance, it may turn out that the psychological adaptations that facilitate the rehearsal of action schemata interact with other psychological adaptations, and such that the latter adaptations bias the manner in which mental rehearsals are generated and evaluated. Furthermore, psychological adaptations can also operate in ways that are beneath the conscious awareness of individuals. This issue appears to be rather complex and rather tricky to arbitrate absent more empirical details. From the point of view of evolutionary psychology, a further complication arises from the fact that psychological adaptations are designed for past environments, not the present. So, all else equal, the capacity to objectively appraise current environmental contexts will be hampered to the extent that the design specifications and or phenotypic expressions of those adaptations are mismatched with the environmental contexts that an individual currently finds themselves within. For instance, since formal education is an evolutionary novelty for which our psychological adaptations are not adapted, when one is deliberating about one's educational prospects, one is engaging in deliberations for which one possesses no psychological adaptations specifically designed for that end—that is to say, we do not possess a psychological adaptation that was designed specifically for the function of thinking about one's educational prospects. Hence, all else equal, there would be greater scope for appraisal errors to be made by individuals, since the appraisal of one's educational prospects would be generated by the cognitive activity of psychological adaptations that are not designed for that end—such adaptations must instead be pressed in the service of making 38
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an appraisal of a situation that is very highly evolutionarily-novel. As a more general upshot, then, mismatches between the designs of psychological adaptations and the contemporary environments that they develop and operate in might make aggressive behavior more likely, even if, objectively, the fitness consequences for various individuals are likely to be worse as a result. Since aggression is by hypothesis taken to be generated by underlying psychological adaptations designed by natural selection to be deployed in certain contexts so as to enhance one's fitness prospects, there is no guarantee that those adaptations will function to that end in modern environments—at least to the degree that those modern environments diverge from the past environments that shaped the adaptations implicated in aggression. To illustrate the foregoing, however, we might imagine a particular scenario in a modern environment in which one's psychological adaptations bias them towards an aggressive action, but where the aggressive action objectively stands a very slim chance of actually increasing that individual's reproductive fitness. However, counterfactually, it may be that the same kind of aggressive action would have stood a higher likelihood of increasing one's fitness prospects ancestrally. Whereas the latter (ancestral) scenario might ultimately garner the individual an increase in status which they then parlay into enhanced reproductive fitness, the former (modern) scenario might lead to a prison sentence and no enhancement of reproductive fitness. In this pair of contrasting hypothetical scenarios, the key difference that makes the difference, roughly speaking, would be the mismatch that exists between the environment and relevant psychological adaptations in one scenario but not the other. Aside from various sorts of mismatch between psychological adaptations and contemporary environments, however, we might expect that aggressive risk-taking generally and accurately reflects one's abilities, and generally and accurately reflects actual advantages and disadvantages in relative-state. But it is quite possible for an appropriate psychological adaptation to erroneously assess which avenues for social success are objectively open to an individual. Accordingly, such a psychological adaptation might simply be unaware of avenues for nonaggressive, legal social success that are in principle available to a given individual. One interesting corollary to this is that certain inclinations towards aggressive risk-taking in at least some individuals might be dampened or perhaps eliminated if the underlying psychological adaptations become “convinced”—by whatever means—that non-aggressive, legal avenues for social success could be effectively traversed. Similarly, individuals could be introduced to ways of gaining status that they were previously unaware of. For instance, perhaps a young man who might otherwise be prone to violent crime, owing to certain disadvantages in abilities, and against the backdrop of currently perceived options for gaining status, can be convinced that, say, broadcasting his singing or acting abilities on social media would grant him the peer esteem that he desires (e.g., Patterson Jr, 2015). Similarly, perhaps an individual otherwise prone to violent crime could be convinced that there were educational opportunities of some kind available to them which could lead to some form of social success that they desire. Empirical tests of these ideas could be conducted, and hypothetical policies could be developed that, for instance, offer aggression-prone individuals options for escaping dangerous living conditions and pursuing newly discovered avenues for social success. Apropos to the topic of reducing aggression, neighborhood residents and (i.e., non-profit) organizations might potentially exert various positive effects on a local community, such that it can have meliorative effects on crime prevalence in that community (e.g., Sharkey, Torrats-Espinosa, & Takyar, 2017). More generally, the adaptationist model developed in this paper is also compatible with the idea that individuals—including, for our purposes, men—can be dissuaded from considering aggressive risktaking and violent crime as an option by, for instance, reconsidering the manner in which they narratively construe their life (e.g., Peterson, 2002). To this end, Ward and Fortune (2013) discuss a rehabilitation program dubbed the “Good Lives Model”, which, among other things,
aims at helping individuals develop skills and acquire various kinds of supports that could assist them in attaining the kinds of social success that they desire. Moreover, it is quite possible that many men in possession of a disadvantaged relative-state might be more likely to refrain from attempting to gain status through violent means if they were to simulate mating success through the use of prostitutes or sexbots—doing so would, in other words, provide “fake” fitness cues to underlying psychological adaptations, hence satisfy mating drives and thereby curtail if not obviate the drive to use aggression in the first place (Fleischman, 2018). It is possible that the effortless and regular access to sex that prostitutes and sexbots can allow for can provide the psychological adaptations of men with feedback that mimics the cues of actual reproductive success. In other words, it is possible that prostitutes and sexbots might provide the psychological adaptations of men with input that is processed as if they have successfully mated. Prima facie, though, it may seem that this hypothesis is in tension, if not direct contradiction, with the empirical observation that a surfeit of women relative to men in a local mating market is correlated with elevated levels of male aggression. Perhaps this apparent incongruity can be resolved by hypothesizing that the mating competition between men for access to those surplus women becomes more intense, which in turn increases the likelihood of violent confrontations, whereas prostitutes and sexbots might simply circumvent that intense mating competition altogether, or often enough. Hence, effortless and regular access to prostitutes and or sexbots might remove the kind of competition between men that might otherwise be liable to turn violent whenever women outnumber men in a local mating market. In any case, these hypotheses require a good deal of further empirical investigation in order for them to be adequately tested. In light of the considerations raised in this section, clinicians might therefore find some use in evolutionary approaches to understanding male aggression. For example, they may find that it helps in identifying young men who might perceive their prospects for social success to be uncertain—uncertain because such young men perceive themselves to be disadvantaged in some way, relative to their peer group. Of course, according to evolutionary approaches, the ways that people perceive and can come to understand social success will typically mirror the recurrent, fitness-relevant concerns of the evolutionary past—i.e., climbing status hierarchies; being liked or admired by others; finding a mate; etc. But, as should be clear from the approach developed in this paper, there are idiosyncratic aspects to the ways that individuals perceive and come to understand their own prospects for social success. Thus, clinicians working with aggressive individuals might find the evolutionary approach heuristically usefully in that it can help them identify routes to social success that are reasonably within reach of their clients, either now or with some effort. Just as importantly, it can help clinicians identify which of those paths their clients are also likely to see as attainable, meaningful, and as gaining them status. The potential heuristic value that the evolutionary approach can have for clinicians, therefore, has two broad aspects. On the one hand, it helps them zero in on the space of attainable and meaningful non-aggressive alternatives for achieving social success that their clients can pursue. And on the other hand, it allows clinicians to devise this course in a way that makes them sensitive to the idiosyncrasies of their clients that are relevant to devising such an alternative path through life. 9. A Darwinian perspective on war and gangs From a Darwinian perspective, war and the existence of gangs are perhaps unsurprising. For example, among our closest evolutionary cousins, Chimpanzees, troops will sometimes gradually and systematically kill off male members of a rival troop that wander alone near a shared territorial border (e.g., Wrangham & Glowacki, 2012). Indeed, this phenomenon mirrors the coalitional violence seen in our own species. Normally, chimpanzees from one group will attack a member of 39
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a rival troop when that member has been separated from their own troop—for instance, when a lone chimp has wandered to the border separating the territories of two respective troops. Chimps also appear to be more prone to attack other chimps when the attacking coalition is larger than the coalition being attacked, suggesting that they evolved an adaptation designed to track the relative-sizes of coalitions in realtime (Wrangham & Glowacki, 2012). Interestingly, there is also evidence that, when in the presence of other members in their own coalition, humans see solitary individuals from rival coalitions as physically smaller and less muscular, which suggests a parallel between humans and chimps so far as coalitional cognition is concerned (Fessler & Holbrook, 2013). Humans have indeed seemingly evolved a coalitional psychology designed for tackling the multifarious problems of living within and among coalitions—whether those coalitions are friendly, neutral, or hostile (e.g., Kurzban, Tooby, & Cosmides, 2001; Moya & Boyd, 2016; Tooby & Cosmides, 2010; Voorspoels, Bartlema, & Vanpaemel, 2014). Our overarching psychological adaptation for living in coalitions often also fuses our identity with those very coalitions, and to varying degrees (Swann Jr, Gómez, Seyle, Morales, & Huici, 2009; Swann Jr, Jetten, Gómez, Whitehouse, & Bastian, 2012). And fusing one's identity with a given coalition is at once a mechanism that strongly binds them to a group and raises the probability that, at least under certain conditions, one will experience strong enmity of rival groups, particularly if those rival groups are perceived as infringing on the welfare of one's group (e.g., Tooby & Cosmides, 2010). Various evolutionists have argued that humans evolved psychological and cultural adaptations for waging war with other groups (as well as peaceful relations with them) (e.g., Gat, 2009, 2015; Glowacki et al., 2017; Pitman, 2011).6 Such a view squares with archaeological, ethnographic, and historical evidence. Supplemental to this (as already mentioned) is evidence that humans have evolved a psychological adaptation for living in coalitions, and, on the flip side, dealing with other coalitions, at least some of which are likely to be rivals. At any rate, assuming that humans have adaptations that evolved for war, they are highly sensitive to many factors and hence do not ineluctably impel humans to be warlike, much less to actually engage in war. A key question, however, is that given that raids and battles against rival groups are intrinsically quite risky for even those individuals comprising the attacking coalition, why would men have evolved to participate in such attacks in the first place? Another question closely related to this one is why such motives for participating in war would have evolved in the first place, given that, over evolutionary history, individual men could have simply let other men in their groups do the risky attacking and then simply shared in the spoils of war. However, given elementary evolutionary considerations, if such spoils of war were distributed evenly or randomly to men in a given group irrespective of their participation in such wars, then the psychological adaptation underlying the propensity to participate in war would have been purged by natural selection. Specifically, the psychological adaptation underlying war would have been removed owing to the fact that participators would have had lower evolutionary fitness than their free-riding peers. Since this all seems paradoxical given the evidence that exists in support of psychological and cultural adaptations for war, it suggests that the above questions must have answers—that such prima facie problems were in fact solved by natural selection. Indeed, it has been argued that men do possess various motivations for war, and by which, crucially, they can derive fitness benefits. Specifically, men can often gain increased status within their coalitions through their participation in war—and especially for acting in ways
considered valuable and brave by their coalitions, including war heroism (Glowacki & Wrangham, 2013; Rusch, Leunissen, & van Vugt, 2015). And such status can of course lead to reproductive success, either directly through access to more and or better quality mates, or indirectly through, for instance, deference from others, more and or better allies, and so forth (e.g., von Rueden et al., 2010). Furthermore, other sources of possible benefits include capturing women from rival groups, and or stealing valuable items. Hence, in spite of the serious risks to life and limb, the psychological adaptation underlying war can, under the right sorts of conditions, galvanize men to participate in battles and raids, and so on. From an ancestral point-of-view, it is also plausible that groups came to blows over animal game, since the latter are likely to have moved across the landscape in such a way that disregarded any established territory that groups may have claimed for themselves (e.g., Gat, 2015). And, given that animal game was such a limited and crucially valuable resource throughout human evolution, there would have been ample incentive to at least sometimes disregard territorial boundaries, or at least compete with other groups for such animal game. Thus, there was more than enough room for tensions between groups to build up over access to such a prized resource. It is worth noting, however, that there are various reasons why participation in war might be compelled rather than because individuals derive benefits from their participation—for instance, there can be cultural institutions in place within a group that enforce punishment on those who fail to participate, or who fail to participate adequately, in war activities (Mathew & Boyd, 2011; Zefferman & Mathew, 2015). With regard to war and gangs, there is also scope for understanding their cultural aspects in terms of cultural group selection (e.g., Turchin, 2007, 2010; Turchin, Currie, Turner, & Gavrilets, 2013). For instance, when groups aggressively compete with one another with some frequency, cultural differences between those groups can, all else equal, make one more likely to ultimately prevail over the others. All else equal, then, certain cultures—or certain cultural beliefs, cultural values, or cultural practices—make for more aggressively formidable groups. For instance, in discussing the role of warfare in the rise of empires within the context of cultural group selection (or multi-level selection), Turchin (2007) notes the observation of the medieval historian Ibn Khaldun, who argued that certain cultures possessed greater levels of trust and cohesion—what he referred to with the Arab word “asabiyyah”—and which made them more effective in battle. Indeed, as Turchin (2007) argues, war can facilitate cultural evolution and, ultimately, the selection of certain cultural groups over others. It is perfectly reasonable, therefore, to examine the degree to which the various cultures of gangs and warring tribes have been shaped by processes of cultural group selection: namely, the degree to which aspects of their cultures have been selected-for (via the natural selection of units of cultural information) within the context of aggressive competition between those cultural groups. For instance, one might imagine the cultures of two warring tribes—or two gangs—coming to valorize ferocity more and more, and such that one tribe's culture comes to valorize ferocity even more as a result of the other tribe's culture elevating their own valorization of ferocity. Thus, both cultures can feedback on each other and thereby mutually increase their respective cultures' valorization of ferocity—they can, in order words, become enveloped by a ferocity spiral. And this kind of cultural evolution can even occur without any particular individuals consciously intending to change their culture in this manner (Dennett, 2017). Recent work on the “male warrior hypothesis” (McDonald, Navarrete, & Van Vugt, 2012) can also help shed light on some of the other aspects of evolved male psychology that might contribute to gang phenomena. Briefly stated, however, a core part of the male warrior hypothesis contends that men have evolved an inclination, under certain conditions, to join coalitions with other men and engage in conflict with other coalitions so as to gain access to fitness-enhancing resources, such as territory, food, and women. For example, for men whose relative-state is especially disadvantaged, joining a gang will often be a
6
The discussion of war in this section does not aim at explaining the unique aspects of warfare at or above the so-called “military horizon”. The focus of this section, rather, is warfare beneath the military horizon, which, as Pinker (2011) puts it, pertains to “the raids, ambushes, skirmishes, turf battles, feuds, and depredations that historians dismiss as ‘primitive’ warfare” (p. 199). 40
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tempting option, even if some or many men realize the inherent dangers of doing so. Simply put, since such men are disadvantaged in the pursuit of social success, gangs can offer the opportunity of gaining the status and resources that are otherwise difficult for them to obtain. Hence, an individual with low relative-state may find themselves especially receptive to coalitions (i.e., gangs) that market themselves in ways that are attractive to those looking for a path to life success—i.e., status and mating opportunities. For instance, this same sort of path to a violent lifestyle is not entirely dissimilar to the manner in which some men are attracted to the messaging of coalitions animated by violent jihad (Atran, 2010; McCauley & Moskalenko, 2010; Taşpınar, 2009). Whether a street gang or extremist organization, such coalitions appeal, whether explicitly or implicitly, to central Darwinian motives of men, particularly a desire for status and mating opportunities (e.g., Thayer & Hudson, 2010). Alternatively (or in conjunction with the above), such coalitions might offer an enticing opportunity for individuals with needs that are difficult for them to meet in non-violent ways, such as to satisfy drug addictions. Furthermore, the existence of local gangs can also present individuals with the threat of being exploited and physically harmed (e.g., O'Flaherty & Sethi, 2010). So, given the fact that gangs can simultaneously be a source of opportunity and threat for certain individuals, there will often be ample incentives for them to join one. A Darwinian understanding of gangs can also underscore the need for adequate policing to help curb the conditions that can help generate them in the first place. Most straightforwardly, Hobbesian-like conditions of anarchy that conduce to gang formation are most likely to be found in pre-state societies and failed states (Wrangham & Wilson, 2004). For under such conditions, there is no “Leviathan”—no overarching authority and policing mechanism—that can oversee the security of individuals, impartially enforce rules, and mete out punishment for violations of such rules. Likewise, once one gang has formed in a given location, it simultaneously creates a pressure for non-members to either join it or join together in a gang of their own, if for no other reason than to provide themselves with protection against that gang. In addition, honor can function at the level of coalitions—in this case, at the level of gangs. For instance, one gang might be widely perceived as “weak”—in particular, less likely or capable to defend against and avenge attacks and poaching. Under such conditions, and all else equal, we might expect that particular gang to more frequently be targeted by rival gangs, or to proactively attempt to elevate their honor. The dynamics of honor at the level of gangs can also spiral out of control, as when two or more gangs get caught in continual cycles of attack and counter-attack, which can quickly slide into a perpetual state of conflict between rival gangs. In such a case, all parties also have an incentive to stand their proverbial ground and maintain a reputation for toughness—that is to say, as a gang that is to be reckoned with and not taken advantage of or otherwise disrespected. In addition, individual gang members might also be incentivized, one way or another, to raise their rank within their gang by stealing from, physically attacking, or outright killing a member of a rival gang, all of which can add even more fuel to the fire of hostilities between gangs. From an evolutionary point of view, such actions can signal to fellow gang members that one has a variety of useful, valuable qualities that they bring to the gang and that they are committed to it, all of which increases their status within the gang and can even showcase their capacity to function in a leadership position (e.g., Donovan, 2012; Van Vugt, 2006). And, of course, petty disputes between members of rival gangs can also give rise to acts of violence, such as assault and homicide. Likewise—and to take one example—violent conflict between gangs can be sustained when they battle for hegemony over drug dealing in a local area. In sum, although gangs caught in the midst of such a destructive dynamic would objectively be better off if they could manage an armistice or sustained peace, insofar as the context in which their interactions occur is characterized by anarchic-like conditions, it will be difficult to interrupt their mutual hostilities. For without strong third-
party institutions to intervene and provide security or justice (i.e., police and courts), there is less incentive to cease their reciprocal and incessant violent antagonisms, all else equal. At root, and according to an evolutionary perspective on honor as it functions at the level of gangs, one of the central engines fueling such hostilities is a reputation for honor—a reputation that gangs seek to maintain and broadcast. 10. The evolutionary genetics and heritability of aggression A number of biosocial criminologists have attempted to illuminate aggression (as well as crime and delinquency more generally) in terms of its heritability. Here, my aim will be twofold: First, to bridge behavior genetics with the explanatory model developed in this paper, and then to briefly discuss the evolutionary processes that can act to generate heritable variation in traits connected to male aggression. Heritable variation in violent crime has been established by behavior geneticists (e.g., Barnes et al., 2014; DiLalla & Gheyara, 2011; Ferguson, 2010; Rhee & Waldman, 2002).7 On the one hand, these studies show us how much of the variance in a given population, at a given time, can be explained by heritable factors. Yet on the other hand, heritability studies are largely silent on the mechanistic and developmental details that subserve the heritability of traits. In order to see how these two sides of the coin are interrelated, we can start by considering the concept of reactive heritability, which sketches how heritable traits express or magnify themselves developmentally (e.g., Tooby & Cosmides, 1990; von Rueden, Lukaszewski, & Gurven, 2015). To illustrate how such processes can work, we can consider an example germane to aggression, whereby an individual inherits above average physical strength. From the figurative point-of-view of the underlying psychological adaptations that govern aggression (broadly speaking), and all else equal, it is unknown what the level of physical strength is in the organism that the adaptations are developing and operating in. However, it is possible that natural-selection can design such adaptations so that they can assess what the agent's physical strength level is—perhaps, for instance, by attending to feedback regarding how often, and to what degree, the agent is either successful or unsuccessful in physical conflicts of interest with other agents. Given these assessments, the underlying psychological adaptation can then compute an overall index of the agent's physical strength, and then utilize that index when judging if and when to instrumentally mete out aggression. Whether such an adaptation has actually evolved, and, if so, what its design features are, are of course empirical questions. However, evolutionary psychologists have indeed found experimental evidence that suggests that a psychological adaptation has evolved in men that can assess one's physical strength, and then use that assessment as an “internal regulatory variable” which governs, for instance, one's proneness to use anger as a bargaining tactic during conflicts of interest with other agents (Sell, Cosmides, et al., 2009; Sell, Tooby, & Cosmides, 2009). Similarly, one possible route through which lower levels of general intelligence—which is also quite heritable as a trait (e.g., Bouchard Jr, 2004; Bouchard & McGue, 2003; Plomin & Deary, 2015; Sniekers et al., 2017)—might in some cases give rise to violent crime, at least in contemporary environments, is via the feedback that those in possession of low cognitive ability receive. For example, and as discussed earlier, since cognitive ability is a strong predictor of academic success and educational attainment, low cognitive ability thereby places a constraint (at least to some degree) on what one can achieve in this regard. Accordingly, and else equal, one's economic prospects will hence be likewise constrained, since cognitive ability is a significant factor (albeit certainly not the only factor) that, on average, increases one's 7 Heritability measures are measures of variance in particular traits in certain populations at a given time. In principle, heritability measures can be different for different populations and they can change when causally relevant aspects of the environment change.
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economic prospects, at least in modern societies (e.g., Murray, 2013)—and so inheriting low cognitive ability is more likely to lead to poorer educational attainment, which in turn constrains one's economic prospects. And as outlined earlier in this paper, appraisals of which avenues for social success are available to a given agent, whether explicit or implicit (or a combination of both), can interact with processes such as the one just sketched. Thus, one can imagine circumstances in which certain individuals, for whatever reasons, think and feel that their prospects for social success are limited, which, in addition, can be exacerbated by low levels of general intelligence (at least in circumstances where low general intelligence limits one's educational prospects). So, in cases where one's relevant psychological adaptations have computed one's prospects for social success as poor, and as partly informed by developmental processes that interact with heritable traits such as general intelligence and conscientiousness, the psychological adaptations that underlie instrumental aggression, for example, may hence be more likely to impel the agent to aggressive, violent crime, at least in certain contexts. Similarly, this same trajectory might also raise the likelihood that an individual will consider joining a gang or other forms of organized crime, since those options might provide some prospects for social success that are otherwise assessed to be less likely. Recall, again, that heritability studies, though quite illuminating and very interesting in their own right, do not necessarily disclose much about the ways that heritable traits manifest themselves mechanistically (including througout development). Apart from processes of reactive heritability, a second way in which heritable variation in traits can manifest themselves is in a more direct fashion, namely by leading to developmental changes in the brain, oftentimes very early in ontogeny. For example, this more direct pathway manifests when a certain allele (gene variant) is shown to reliably cause a specific difference to some aspect of the brain and its functioning, typically very early in ontogeny. It is also important to point out that reactive heritability and the more direct manifestations of heritability—via more directly observable influences on the structure and functioning of the brain—are not necessarily mutually exclusive. So while it is possible in principle that either type of manifestation could account for some or even much of the heritable variance in traits related to aggression, it is quite possible that both kinds of processes are involved. For instance, one process might explain some traits while the other process explains other traits; or some or many traits might be explained by some combination of both processes: that is, certain traits might take on a certain form for congenital reasons very early in ontogeny and then be modified via the process of reactive heritability during development. Furthermore, a given trait might be flexibly calibrated over development in some individuals via reactive heritability and or responses to phenotypic and environmental factors, while perhaps being set by congenital factors in other individuals via direct genetic effects on the brain—and so a given trait might be affected by either such pathway in different individuals (e.g., Glenn, Kurzban, & Raine, 2011). Additionally, processes of reactive heritability, presuming they exist, can combine their effects with adaptations that respond in flexible ways to phenotypic and environmental contingencies. Hence, a given trait might be calibrated to an extent by a process of reactive heritability—whereby, say, a regulatory variable gets computed over the course of development by a psychological adaptation functionally-specialized to do so in response to certain heritable traits—which then is calibrated further—upwards or downwards—depending on other factors, such as, for example, one's relative-state, which itself can be at least partly influenced by heritable traits. In any case, and once again, the precise details must obviously be ascertained empirically. Importantly, however, the variance in aggression (or violent crime more generally) that can be accounted for by congenital damage, such as deficits in prefrontal cortex, might turn out to be quite high (e.g., Raine, Stoddard, Bihrle, & Buchsbaum, 1998). Thus, this possibility should serve to make us cognizant of the fact that certain aspects of the evolutionary model being developed in this paper might in the last analysis only be able to account for a modest amount
of male aggression once causes such as brain lesions and congenital factors such as brain abnormalities are accounted for. A separate question to the above pertains to the evolutionary source of heritable variation itself, and regardless of how such variation manifests mechanistically and developmentally. The two main types of evolutionary processes of relevance to this question are balancing-selection and mutation–selection balance. One form of balancing-selection occurs when more than one allele (i.e., gene variant) is maintained within a given gene pool owing to the fact that each of those alleles possesses equal fitness effects, on average. This can occur when each allele provides fitness benefits in certain spatial environments, or when each allele provides fitness benefits at certain times. For instance, an allele that gives rise to a certain kind of coloration in an organism could prove fitness-enhancing in certain patches within an ecological niche, but not in other patches, and an allele that causes an organism to forage for longer periods of time (relative to other organisms in possession of a different allele) could prove fitness-enhancing during certain generations, but not during others. Each of these sorts of fitness benefits, therefore, can maintain the corresponding alleles in the gene pool, since the fitness costs of a particular allele, whether at given spatial locations or temporal durations, are balanced by fitness benefits at other particular spatial locations or temporal durations. One possibility hereabouts is that alleles that underlie a propensity for aggression have been accordingly selected-for in the past, and are now found at certain frequencies within populations. For example, it is possible that certain alleles, such as the 2-repeat allele of the MAOA gene (e.g., Beaver, Wright, et al., 2013)—the so-called “warrior gene”—have been naturally-selected through the process of balancing-selection because they provided a fitness benefit to their bearers, on average. A second form of balancing-selection can occur when the fitness of a given allele is contingent on its prevalence within a particular population, otherwise known as frequency-dependent selection. For instance, certain alleles that underlie psychopathy might have been maintained at certain frequencies within certain populations because, at those given frequencies, psychopathy was—and perhaps still is—a social strategy that paid off in terms of fitness (e.g., da Silva, Rijo, & Salekin, 2015; Glenn et al., 2011; Mealey, 1995; Međedović, Petrović, Želeskov-Đorić, & Savić, 2017). However, if this kind of scenario can account for at least some of the heritable variance in psychopathy, it is likely that the underlying alleles are kept in balance through frequencydependent selection, which is a manifestation of balancing-selection that, in this case, would reduce the frequency of the underlying alleles when and if they exceeded a certain frequency. The idea here is that psychopathy, as a manipulative and predatory social strategy, was over some stretch of evolutionary time fitness-conducing, on average, but only insofar as, for instance, psychopaths did not encounter other psychopaths—which is a scenario that would have likely proved to be especially fitness-diminishing. The higher the frequency of the underlying alleles, however, the more likely they will be to encounter one another, all else equal. Hence, frequency-dependent selection can act to reduce the frequencies of such alleles once they rise above a certain level, thereby keeping those gene variants fit (that is, fitness-conducing) within a given population. At any rate, with regard to balancing-selection, it remains an open question whether some or much of the heritable variation in aggression—via traits such as psychopathy, for example—has been maintained over evolutionary time because aggression provided a fitness advantage in certain contexts. The other main type of evolutionary process that can maintain heritable variation, mutation–selection balance, occurs whenever the rate of harmful, fitness-reducing mutation outstrips to some degree the rate at which selection is able to remove such mutations from a given gene pool (e.g., Keller, 2008; Keller & Miller, 2006). In general, the number and effects of mutations vary between individuals, with each individual carrying an overall “mutation load” that has gradually accumulated over the generations of one's lineage. It is possible that much of an individual's relative-state and absolute state can be illuminated 42
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through the lens of mutation–selection balance, as the overall mutation load possessed by an individual can act to handicap them in various ways with regard to the traits that contribute to social success in general (whether in contemporary or ancestral environments). It is possible, for instance, that mutations can affect a trait like general intelligence (e.g., Yeo, Gangestad, Liu, Calhoun, & Hutchison, 2011). In which case, to the extent that general intelligence is connected to male aggression, the underlying heritable variation in male aggression will owe its source at least to some degree to mutation-selection balance, since it contributes to heritable variation in general intelligence. As another example, differences in self-control can explain some proportion of variation in male aggression (e.g., Moffitt et al., 2011). And some proportion of the variation in self-control, being heritable, perhaps owes some of its source to underlying mutations and is hence maintained by mutation–selection balance. In general, it remains to be seen how much of the heritable variation in male aggression can be explained by mutation–selection balance, and via which traits in particular it disrupts the functioning of.
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J. Klasios honor. Evolutionary Psychology, 3(1), 147470490500300126. Sharkey, P., Torrats-Espinosa, G., & Takyar, D. (2017). Community and the crime decline: The causal effect of local nonprofits on violent crime. American Sociological Review, 82(6), 1214–1240. da Silva, D. R., Rijo, D., & Salekin, R. T. (2015). The evolutionary roots of psychopathy. Aggression and Violent Behavior, 21, 85–96. Sniekers, S., Stringer, S., Watanabe, K., Jansen, P. R., Coleman, J. R., Krapohl, E., & Amin, N. (2017). Genome-wide association meta-analysis of 78,308 individuals identifies new loci and genes influencing human intelligence. Nature Genetics, 49(7), 1107. Sterelny, K. (2012). The evolved apprentice. MIT press. Swann, W. B., Jr., Gómez, A., Seyle, D. C., Morales, J., & Huici, C. (2009). Identity fusion: The interplay of personal and social identities in extreme group behavior. Journal of Personality and Social Psychology, 96(5), 995. Swann, W. B., Jr., Jetten, J., Gómez, Á., Whitehouse, H., & Bastian, B. (2012). When group membership gets personal: A theory of identity fusion. Psychological Review, 119(3), 441. Taşpınar, Ö. (2009). Fighting radicalism, not "terrorism": Root causes of an international actor redefined. SAIS Review of International Affairs, 29(2), 75–86. Thayer, B. A., & Hudson, V. M. (2010). Sex and the Shaheed: Insights from the life sciences on Islamic suicide terrorism. International Security, 34(4), 37–62. Tooby, J. (2014). Learning and culture. Retrieved from Edgehttp://www.edge.org/ response-detail/25343. Tooby, J., & Cosmides, L. (1990). On the universality of human nature and the uniqueness of the individual: The role of genetics and adaptation. Journal of Personality, 58(1), 17–67. Tooby, J., & Cosmides, L. (2010). Groups in mind: The coalitional roots of war and morality. Human morality and sociality: Evolutionary and comparative perspectives (pp. 91–234). . Tooby, J., & Cosmides, L. (2015). The theoretical foundations of evolutionary psychology. In D. M. Buss (Vol. Ed.), The handbook of evolutionary psychology(Second edition). 1. The handbook of evolutionary psychology (pp. 3–87). Foundations. Hoboken, NJ: John Wiley & Sons. Tooby, J., Cosmides, L., & Barrett, H. C. (2003). The second law of thermodynamics is the first law of psychology: Evolutionary developmental psychology and the theory of tandem, coordinated inheritances: Comment on Lickliter and Honeycutt. Vol. 2003. Trivers, R. L. (1972). Parental investment and sexual selection. In B. Campbell (Ed.). Sexual selection and the descent of man: 1871–1971 (pp. 136–179). Chicago: Aldine. Turchin, P. (2007). War and peace and war: The rise and fall of empires. Penguin. Turchin, P. (2010). Warfare and the evolution of social complexity: A multilevel-selection approach. Structure and Dynamics, 4(3). Turchin, P., Currie, T. E., Turner, E. A., & Gavrilets, S. (2013). War, space, and the
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Contents lists available at ScienceDirect
Aggression and Violent Behavior journal homepage: www.elsevier.com/locate/aggviobeh
Aggression among men: An integrated evolutionary explanation John Klasios
T
Toronto, Ontario, Canada
ARTICLE INFO
ABSTRACT
Keywords: Aggression Violence Evolution Evolutionary psychology Men Culture
This paper develops an integrated theoretical explanation of aggression among men, showing that much of that aggression is anchored in naturally-selected psychological adaptations—and, in the case of honor, importantly tied to cultural transmission—designed to solve the recurrent evolutionary problems of status and honor. Both of these problems are—or at least were—very crucial to the reproductive success of men. Maintaining and cultivating honor, engaging in theft, mating competition, war, and gangs are the main phenomena thereby explained in evolutionary terms. Drawing on theoretical and conceptual resources from the evolutionary sciences at large, and in particular evolutionary psychology, the explanation developed here also and importantly pulls together the psychological, developmental, cultural, and ecological dimensions of the phenomena at issue. Doing so allows the model to sketch the ways in which the psychological adaptations underlying aggression are sensitive to both external and individual contingencies and thereby open-ended and flexible. The evolutionary model developed here draws an additional strength from its ability to grapple with individual differences and evolutionarily-novel environments. Finally, the integrated explanation is also synthesized with the evolutionary genetics and heritability of aggression.
So that in the nature of man, we find three principal causes of quarrel. First, competition; secondly, diffidence; thirdly, glory. The first maketh men invade for gain; the second for safety; and the third for reputation. The first use violence, to make themselves masters of other men's persons, wives, children and cattle; the second, to defend them; the third, for trifles, as a word, a smile, a different opinion, and any other sign of undervalue, either direct in their persons or by reflection in their kindred, their friends, their nation, their profession, or their name. —Thomas Hobbes, The Leviathan, 1651 1. Introduction In this paper, I will develop an integrated theoretical explanation of aggression among men. The theory to be developed will have its foundations in evolutionary psychology and will therefore make use of its conceptual and theoretical resources. Specifically, the explanatory account will develop the view that aggression has been partly shaped by natural-selection so as to help solve the recurrent evolutionary problems of status and honor. Accordingly, the theory will attempt to explain how certain kinds of male aggression are strategically deployed in service to these two ends. Haig (2014) has argued that sound method in psychology and the behavioral sciences has, as one of its many features, a capacity and openness to engage in partial and even provisional
model building that is importantly connected to the general explanatory approach of abductive reasoning, otherwise known as inference to the best explanation. The approach taken in this paper should accordingly be seen in that same spirit. Thus, the theory developed here ought to be construed as very much open to being developed in further detail and amended where appropriate. Accordingly, there will be many places in this account that explicitly or implicitly call for further scientific work, in order to arbitrate questions and or fill in further details. So, the project pursued here is not merely one of theoretical synthesis and model building, but also an outline of how a larger research program could proceed in order to more fully develop an evolutionary-psychological understanding of aggression among men. Ultimately, it would be desirable if the explanatory model developed here were compared with other competing theories that aim to explain the same phenomena, and such that they are competitively assessed using a framework that places important emphasis on certain explanatory virtues, such as the approach generally known as inference to the best explanation (Durrant & Haig, 2001; Haig, 2014). It is important to stress that at least some aspects of the model developed here require more empirical testing. In general, and like any explanation in science, adaptationist explanations can come in varying strengths, depending on the amount, type, and quality of evidence that has accrued both in their favor and against them. One can even construe their likelihood of being correct in Bayesian terms, if one finds
E-mail address: [email protected]. https://doi.org/10.1016/j.avb.2019.02.015 Received 5 June 2018; Received in revised form 10 January 2019; Accepted 26 February 2019 Available online 13 March 2019 1359-1789/ © 2019 Elsevier Ltd. All rights reserved.
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that assessment approach fruitful. Indeed, some aspects of the model developed here should be understood as hypotheses rather than explanatory theories—including hypotheses that would be relatively difficult to test, either directly or indirectly. Although prior work aiming to develop an overarching theory of aggression—and crime more generally—has drawn from the evolutionary sciences at large (e.g., Barber, 2009a; Barnes, Boutwell, & Beaver, 2015; Boutwell et al., 2015; Buss & Shackelford, 1997; Durrant & Ward, 2015; Ferguson, 2011; Goetz, 2010; Keller, 2017; Pinker, 2011; Walsh, 2006; Walsh & Beaver, 2009; Wiebe, 2012; Wilson & Daly, 1985), there are still many possible avenues to be explored.1 Hence, the theoretical account developed here will build on prior work as well as draw on conceptual and empirical insights from evolutionary psychology that have, to my knowledge, been heretofore unexplored in the context of understanding the dimensions of male aggression related to status and honor. The main focus of the theory developed here will be on men, for reasons that will emerge throughout. A core reason for this, however, is that, all else equal, men are faced with adaptive problems that differ in some crucial ways from women (Campbell, 2013). In particular, various forms of competition between men are a core route through which men achieve reproductive fitness, although the form of this competition need not always involve direct physical aggression between men. However, in various circumstances, aggression is often a risky but adaptive strategy for attaining or retaining status or honor, both of which are important to men's evolutionary fitness (as will be shown). From a phylogenetic point of view, it may turn out, for instance, that the psychological adaptations implicated in aggressive risk-taking are found in homologous forms in other taxa. Or adaptations for risktaking might possibly have even evolved in other taxa via convergent evolution, whereby two or more lineages evolve the same trait independently of one another—as in the case, for instance, of the evolution of flight in birds and insects. Indeed, in the later discussion of war and gangs, we will see similarities emerge between humans and chimps. Phylogenetically speaking, there is reason to think that certain kinds of aggression found among men—and humans more generally—have been selected-for across a large swath of evolutionary time and thus are present in some form in other species as well. From a developmental point of view, there may also be ways in which various learning adaptations are implicated in making one prone to aggression—for instance, via processes that look similar to operant conditioning. Among primates, reproductive variance among males is linked to sexual dimorphism, and this is concordant with the fact that species with larger differences between the sexes in various traits—such as differences in average size—are also those that tend to exhibit larger skews in reproductive success among males (e.g., Archer, 2009; Puts, 2010). And like other primates, humans also exhibit sexual dimorphism, which suggests that men descend from ancestors who often engaged in risky and violent competition with one another—at least often enough, evolutionarily-speaking. Indeed, our close evolutionary relatives, chimpanzees, are also known to use aggression in ways relevant to genetic fitness (e.g., Glowacki, Wilson, & Wrangham, 2017; Wrangham & Glowacki, 2012). A key upshot of these considerations, therefore, is that men are likely to possess a corresponding psychological nature that appropriately reflects our evolutionary history of risky and violent status competition in service of reproductive fitness. In some cultures, such as the Yanomamo, the use of violence by men—particularly the homicide of other men—is closely associated with increased status and thereby reproductive fitness (Glowacki et al., 2017). Indeed, some evidence suggests that criminality is associated with
increased reproductive success, at least in some contemporary societies, and might conceivably reflect an alternative, naturally-selected strategy (e.g., Yao, Långström, Temrin, & Walum, 2014). And some Darwinian psychologists have even hypothesized the existence of a psychological adaptation functionally-specialized for planning and carrying out homicide (Duntley & Buss, 2011). 2. A science of human nature One of the virtues of evolutionary psychology is its aspiration to integrate relevant theoretical insights and empirical findings from the evolutionary sciences, natural sciences, and social sciences. One upshot of such an approach is the realization that disciplinary boundaries are often an impediment to understanding various naturalistic phenomena, particularly those that cut across different domains of scientific inquiry. To this end, I will contend that understanding violence among men should ultimately be placed on an evolutionary foundation. In modern evolutionary psychology, for instance, work has been done on both the universal aspects of the human mind and those aspects that vary between conspecifics (i.e., sex differences, individual differences). In considering the ways in which an evolutionary approach might be applied to the theory developed in this paper, we should be open-minded about how both universal and variable aspects of our evolved psychology may give rise to violence. One of the principal aims of evolutionary psychology is to develop a mature and rigorous science of human nature. And like much if not all of the natural sciences at large, one of the primary aims of evolutionary psychology, if not the primary aim, is to achieve the kind of explanatory unification which brings with it an understanding of how broader classes of phenomena are caused by underlying causal mechanisms. In particular, this would ultimately be an explanation of human cognition and behavior in terms of the mechanisms instantiated in the brain that were shaped by natural selection (viz., via blind variation of heritable traits and environmental filtration). The community of researchers pursuing this goal avail themselves of anything of relevance from branches of science such as neurobiology, cognitive science, anthropology, economics, and, of course, evolutionary biology (though this is not an exhaustive list of tributary disciplines). To begin with, I will outline a framework that has been developing in recent years within evolutionary psychology. Such a framework will (I contend) serve as a good foundation on which to formulate an explanatory account of aggression among men. 3. Evolutionary psychology: central concepts According to various evolutionary psychologists, the mind is comprised of a collection of functionally-specialized psychological adaptations (Barrett & Kurzban, 2006; Tooby & Cosmides, 2015). Psychological adaptations are biological adaptations, and biological adaptations are a widespread (Dawkins, 1986; Dennett, 1995; Williams, 2008) and, for many, very explanatorily important feature of the living world (Godfrey-Smith, 2001). And like biological adaptations more generally, each of these psychological adaptations possess an evolutionary history which shaped it—via natural selection—to perform a function (or multiple functions), roughly speaking. Although any given psychological adaptation may have been shaped gradually over extremely long periods of evolutionary time, evolutionary psychologists are often most interested in psychological adaptations—or elements of psychological adaptations—which were substantially if not mainly shaped and solidified over the last 2.5-million years, approximately speaking. It is this range of evolutionary time that evolutionary psychologists often refer to as the “Environment of Evolutionary Adaptedness” (or simply the “EEA”). Each psychological adaptation can be said to have an EEA, which, conceptually speaking, encompasses any and all of the selection pressures that were causally implicated in the shaping of the adaptation in question—and, in this sense, psychological adaptations are no
1 Some non-evolutionary explanations of crime, such as the one developed by Agnew (2016), are roughly compatible with evolutionary explanations and overlap with them to varying degrees.
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different from any other biological adaptation in the living world, as all adaptations owe their etiology to particular selective forces that have acted throughout historical time. To briefly illustrate the manner in which psychological adaptations are connected to their corresponding selective histories, we can consider disgust, which evolutionary psychologists have posited as a psychological adaptation (e.g., Tybur, Lieberman, Kurzban, & DeScioli, 2013). Concisely speaking, one of the postulated functions of disgust is to adaptively guide individuals away from substances—i.e., foods, excrement—close contact with which would not conduce to fitness—for in ingesting a poisonous food substance, say, an individual's survival and reproductive prospects might very well be interfered with, such that their fitness prospects would be better had they not ingested it. Current understanding of psychological adaptations within evolutionary psychology sees them as relatively responsive to environmental inputs of varying sorts, be they endogenous (events within the confines of the organism) or exogenous (events originating in the external physical ecology or cultural environment, etc.). A very useful way of conceptualizing the responsiveness of psychological adaptations at a relatively abstract level is to view them under the lens of the type/token distinction (Barrett, 2006). For instance—and to foreshadow an issue that will arise later—consider a psychological adaptation functionally designed to attend to honor—or, more specifically, anything pertaining to an “honor culture” and the standing of one's honor within their local social environment. In such a case, dealing with the existence of an honor culture (generally speaking), and assessing one's standing within it, would be the type of ancestral problem that the psychological adaptation evolved to solve. However, the exact details of one's particular honor—namely the reputation for honor that one actually has among their social peers at a given time—would be a token of the aforementioned type of ancestral problem. In this sense, a type description of a psychological adaptation specifies its design in relatively broad terms, whereas a token description is a more refined and detailed description of various manifestations of the psychological adaptation in view of its particular developmental history in a particular agent. Psychological adaptations are also properly seen as evolved developmental systems (as per evolutionary developmental biology), and so they each have an underlying logic which instantiates itself throughout development (Tooby, Cosmides, & Barrett, 2003). Barrett (2015) has developed a very useful understanding of psychological adaptations, according to which the type of ancestral problem for which a psychological adaptation evolved to solve is specified by its design space—its functionally-specialized, naturally-selected rationale(s). Correspondingly, the token expressions of a psychological adaptation are embodied in its phenotype space—its particular manifestation in any given individual at a given time. The functionally-specialized design space of a given psychological adaptation can also be conceptualized as inhabiting some region of an even larger design space, which can be construed as a massively multidimensional space of all hypothetically possible psychological adaptations that could arise in a biological organism. The manifestation in phenotype space of a given psychological adaptation in a given individual at a given time, on the other hand, can be conceptualized as inhabiting some region of an even larger phenotype space, which can be construed as a massively multidimensional space of all hypothetically possible phenotypic expressions that could arise in a biological organism. An adaptation's design space is intimately related to its phenotype space. Broadly speaking, an adaptation's particular design space developmentally interacts with the “environment” (viz., all causally-relevant properties and events) in particular ways, and such that a particular phenotype emerges through that interaction. So, an adaptation's design space can be conceptualized as all—or at least many—of the phenotypic expressions that have been selected-for during the evolutionary history of that adaptation. More generally, however, all of these phenotypic expressions are a subset of the larger phenotype space of all possible phenotypic expressions that might hypothetically be connected to a given adaptation. To reiterate, all of the
phenotypic expressions that have been selected-for during the evolutionary history of an adaptation constitute that adaptation's design space—thus, an adaptation's design space is equivalent to that particular subset of phenotype space. Moreover, an adaptation's design space may—and in many cases, can—give rise to phenotypic expressions that fall outside of the subset of phenotypic expressions in virtue of which that adaptation was selected-for in the evolutionary past. This is effectively the same as saying that an adaptation possesses a reaction norm which can produce a range of phenotypic expressions, and such that its phenotypic expressions depend in certain (often complex) ways on the wider developmental environment. So, the possible phenotypic expressions that can arise out of an adaptation's design space can be entirely novel vis-à-vis the phenotypic expressions that have arisen from that design space in the past lineage of an organism (during which the adaptation was selected-for). Ultimately, however, the phenotypic expressions that are actually possible expressions of an adaptation's design space are a complicated empirical issue that cannot be settled on conceptual grounds alone.2 Henceforth, I will use the term “design”, for short, to refer to an adaptation's design space. Of course, only careful empirical investigation will allow us to understand a given adaptation's design and the manner in which that design developmentally interacts with other psychological adaptations, the agent's body, and environmental variables to give rise to any of its phenotypic expressions. In order to forestall one possible objection, it should be noted that psychological adaptations can be designed to learn and process cultural information, which can accordingly interact with other psychological adaptations in the mind. Another key conceptual and methodological resource is the modeling of psychological adaptations, which in turn are instantiated in evolved developmental systems within the brain. Ultimately, understanding a psychological adaptation in a comprehensive manner would entail possessing a computational model that specifies both its cognitive specifications (e.g., Frankenhuis, Panchanathan, & Barrett, 2013) and the manner in which those specifications map onto the brain (e.g., Bechtel, 2012, 2006). Aiming for this full-blooded style of explanation is unnecessary for a fruitful understanding of psychological adaptations to be had in the interim, of course. Hence, those wishing to gain an evolutionary-psychological understanding of aggression among men need not specify the precise instantiation details of such aggression in terms of evolved developmental systems in the brain, although instantiation details—such as relevant physiological aspects—can most certainly help illuminate the “higher-level” phenomena which they ultimately instantiate, namely cognitive processes (e.g., Platek, Keenan, & Shackelford, 2007; Platek & Shackelford, 2009). Rather, for many purposes, it will be sufficient to develop computational models of the various functionally-specialized psychological adaptations that govern aggression among men. It is beyond the scope of the present paper to explore the manner in which the brain is computational. Those interested in fuller treatments of this topic may wish to consult Marcus (2003) and Gallistel and King (2011). Roughly speaking, computational models of psychological adaptations aim to specify their representations and algorithms, as well as the manner in which those adaptations interact both with the wider environment and the rest of the mind and body. Computational models of psychological adaptations, therefore, permit for scientifically rigorous explanations that integrate the highly complex matrix of cognition, development, and ecology (the latter of which also includes the cultural sphere). In addition to being integrative, an evolutionary-psychological approach allows researchers to aim at carving the mind's nature at its proverbial ontological joints, which is tantamount to providing a schematic of all of the mind's
2 Barrett (2015) provides a comprehensive and in-depth explanation of these issues. This style of abstract scientific modeling is indeed found throughout much of science. A clear and thorough analysis of such abstract and or idealized models is given by Chakravartty (2007, 2010).
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component psychological adaptations. For our purposes, this means computationally modeling the developmental design of the psychological adaptations that underlie aggression among men, including the specific manner in which those psychological adaptations are designed to interact with the wider ecology. Because adaptations are always shaped by past selection processes, understanding their designs will also illuminate if and when their development and operation is dysfunctional—that is to say, mismatched with current environments (e.g., Kanazawa, 2004). The evolutionary-psychological account being developed in this paper, it should be underscored, aims at a “law-like” understanding of aggression between men, and one that aims to have universal scope. Finally, the claim that much about aggression between men can be understood in terms of modeling psychological adaptations absent much if any knowledge of their instantiation details in terms of neurobiology can be buttressed by recalling an episode from the history of science. Namely, one need only recall that Newton's law of universal gravitation was formulated and accepted as a (mathematical) explanation of the phenomenon even though a causal–mechanistic understanding of how gravity worked was wholly absent at the time, and remained unknown until Einsteinian relativity was established at a much later time (although the explanation of gravity provided by general relativity is not in terms of a “mechanism” per se, but rather in terms of space-time curvature). Indeed, as has been pointed out by evolutionary psychologists, discovery of the precise causal–mechanistic implementation details of psychological adaptations—that is to say, their neurobiology—can realistically only proceed once such psychological adaptations have been discovered in the first place. And this means that the manifold cognitive and behavioral regularities of those psychological adaptations need to first be detected and both adequately and progressively modeled in computational terms. To the extent that this is accomplished, neurobiological discovery will be more or less proportionately guided in informed and fruitful ways. Methodologically speaking, Schmitt and Pilcher (2004) and Andrews, Gangestad, and Matthews (2002) provide discussions of how empirical investigators can identify psychological adaptations, interpret their functional rationales, and understand their design features and the ways in which those adaptations develop.
Malamuth, Huppin, & Paul, 2005). Accordingly, one might wish to model the underlying psychological adaptation(s) that might govern such phenomena. To this end, various sorts of questions might be posed, such as what individual traits, in both the perpetrator and the victim, and what kinds of external conditions, might increase (or decrease) the likelihood of the hypothetical adaptation generating violence and threats of violence. It is worth underscoring that the existence of laws and punishments for such behaviors does not foreclose the possibility that there exist underlying psychological adaptations designed to give rise to violent behaviors under certain conditions. Behaviors in modern contexts that do not lead to the maximization of fitness can nonetheless arise from the proper functioning of naturally-selected adaptations, which would be analogous to a naturally-selected penchant for sugary or fatty foods leading some individuals to develop adverse health outcomes through the over-consumption of certain modern foods—such as pastries, ice cream, and French fries, etc.—even if the underlying preference was adaptive in the ancestral past, when the availability of sugar and fat was scarcer. Equally, a hypothetical psychological adaptation that contributes to modern occurrences of violence in some individuals and under certain conditions need not necessarily be fitnessmaximizing in contemporary contexts. So far as reproduction is concerned, a sexually-reproducing animal (such as a human) that persistently lacked any mating opportunities would of course fail to reproduce—although there are other ways in which it could enhance its inclusive fitness, namely by assisting the fitness of its relatives (Burnstein, 2005; Hamilton, 1964). So, we may hypothesize the existence of a psychological adaptation which becomes especially active under conditions in which an individual lacks offspring or persistently lacks mating opportunities. Accordingly, it might be hypothesized that such an adaptation leads them to be more inclined to engage in various forms of behavior, which, at least ancestrally, would have increased the probability of gaining mating opportunities. Of course, this is not to say that such a hypothetical psychological adaptation would operate in an obligate, reflexive manner; on the contrary, psychological adaptations are (or at least often are) highly sensitive to various environmental variables and to the operations of other psychological adaptions in the mind, including careful deliberation. In addition, given human sex-differences that govern obligatory parental investment in offspring (Trivers, 1972), an evolutionary perspective would also suggest the existence of important sex-differences in possible psychological adaptations that underlie the above hypothetical scenario. For instance, it is by dint of asymmetrical demands in parental investment among the sexes that we might also expect men to be more willing to utilize high-risk and even violent strategies to increase their reproductive prospects, even at the risk of serious injury or death (Wilson & Daly, 1985). Since sperm is cheap and ova are not, both sexes have evolved some key differences in mating strategies (e.g., Buss & Schmitt, 1993). Such selection pressures are widespread in the animal kingdom and fall under the general rubric of sexual selection (Andersson, 1994). Accordingly, women, on average, are choosier when selecting mating partners and will have an easier time securing a sperm donor for offspring. Correspondingly, men, on average, are less choosier when selecting mating partners and will have a relatively more difficult task securing ova to inseminate (although, of course, it should be noted that neither men nor women need consciously understand that such naturally-selected rationales underlie their cognition and behavior). So, sex differences in obligate parental investment have led women to evolve to be choosier when choosing mates, all else equal—in particular, in short-term mating contexts (cf. Miller, 2013). Hence, we might expect men to be more likely to deploy risky behaviors in various contexts, such that successful risk-taking in those contexts would tend to enhance their mating prospects. This is especially true—and importantly so—given that women are often seeking men with social status and access to valuable resources (e.g., Buss, 1989). In long-term mating contexts, such men are especially sought after by women due to the fact that such men, owing to their high social status and access to
4. Flexible designs for male aggression One initial first-pass attempt at illuminating the often complex and contingent nature of psychological adaptations is by considering them in the light of life-history theory (e.g., Kaplan & Gangestad, 2005). In its most general sense, life-history theory conceives of animal life as ultimately concerned with survival and reproduction. And it is life-history theory which highlights and attempts to understand the various tradeoffs between these two chief aims. In the case of humans, for instance, reproduction can be partitioned into mating effort and parenting effort, both of which can be traded-off with one another: an individual that decides to allocate time, resources, and energy to raising offspring at any given duration of time forsakes allocating them to the pursuit of another mating partner, and vice versa. It is important at this point to stress, once again, that the designs of psychological adaptations were all shaped by ancestral selection pressures. So, in the context of modern societies, there are no guarantees that they will operate in ways that conduce to biological fitness (viz., reproduction), either in any given individual or within a population in general. Indeed, there is no a priori guarantee that any given adaptation will even develop in a manner entirely congruent with its underlying design. Hence, it may turn out, for example, that certain types of violence were (or plausibly were) adaptive (in the biological fitness sense) in ancestral conditions, but are not (or at least not always) adaptive in modern conditions. For instance, some evolutionary psychologists have hypothesized that violence and threats of violence directed at mating partners may have evolved via natural selection because such behavior was ancestrally adaptive (at least under certain conditions, and at least in a probabilistic sense) (e.g., 32
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valuable resources, can parlay such status and resources into a woman's children, and by extension enhance her reproductive fitness (e.g., Marlowe, 2003; Von Rueden, Gurven, & Kaplan, 2010). Just as importantly, and much like many other species, men evince physical, cognitive, and behavioral features that reflect an ancestral past of at least some degree of aggressive competition with one another (Archer, 2009; Puts, 2010). Such aggressive competition between men would have been over access to women (as mating partners) or over valuable resources, including those resources that women valued in mating partners. In other words, then, men possess many traits that bear the hallmarks of sexual selection, traits which were selected, in this case, because of their adaptive benefits in competition with other men over evolutionary time (Darwin, 1871). Appreciating both the developmental and operational flexibility of psychological adaptations can also lead us to see criminology's wellknown typology of “adolescence-limited offenders” and “life-coursepersistent offenders” in a new light (Moffitt, 1993). For instance, as has been pointed out by Kanazawa and Still (2000), young men often lack some of the attributes which make men attractive long-term partners to women, such as access to resources and other traits. So it is reasonable to think that crimes committed by juvenile males may, at least in part, reflect the kinds of temporary constraints and deficiencies that they are typically beholden to at that phase of life (e.g., Ellis et al., 2012). Thus, the observed pattern of offending carried out by many adolescents may at least partially reflect the operations of some underlying psychological adaptation(s) designed to be strategically active during the phase of life—namely, adolescence—when certain individuals are often illequipped to gain status and valuable resources in a legal, non-violent manner. To put the point another way, such psychological adaptations would accordingly generate certain sorts of cognitive processes and behaviors under appropriate conditions. Such candidate psychological adaptations could profit from further investigation, particularly of the sort that aims to uncover their computational architecture. The view that risky behavior is deployed strategically so as to acquire status and resources, which are ultimately parlayed into reproductive success, is also supported by evidence that men in monogamous relationships are less prone to violence than men either not in monogamous relationships or in relationships but not monogamous (e.g., Seffrin, 2017). So, having obtained a mate and having formed a monogamous relationship with them, a man appears to have much less need and desire to engage in aggressive risk-taking, which underscores the view that aggressive risktaking in service of attaining status and acquiring resources is primarily motivated by mating success, evolutionarily-speaking. With respect to life-course-persistent offenders, one possible hypothesis is that the male mind contains a psychological adaptation for sampling one's social and physical ecology (and one's embodied capital—to be discussed later) for the purpose of assessing what strategies might be germane to fitness. Yet here it should be stressed that in speaking of strategy assessments carried out by hypothetical adaptations, we are specifically speaking of the naturally-selected rationales that would be embodied by their designs. This is, to be clear, importantly and altogether different than saying that an individual can appreciate those rationales. All that needed to occur for those adapted designs (and the genes underlying them) to have been selected-for ancestrally was for them to have increased their bearers' fitness. In terms of strategy, if the mind is by design geared to ascertain various kinds of routes to social success—with social success standing as a proxy for the kinds of status and resources that tend to lead to greater reproductive fitness—then it should be able to use various types of input for the purposes of forming a variegated array of desires, beliefs, and goals to that end. It might be hypothesized, therefore, that such adaptations are designed to generate desires, beliefs, and goals that are, relative to available alternatives, more likely to conduce to social success in one's social and physical ecology (or would have ancestrally). In forming such desires, beliefs, and goals, it might be further hypothesized that other psychological adaptations are also designed to carry out
various sorts of appraisals of one's abilities, alliance partners, and so forth—appraisals, that is, of the various sorts of resources that would have probabilistically indexed one's capacity to attain social status ancestrally, and thereby reproductive success. Both of these cognitive processes—namely, computing what options are available for attaining success, on the one hand, and computing the wherewithal one can bring to bear on trying to attain such success, on the other—can then hypothetically be compared in some manner. In such a case, an underlying psychological adaptation can then—and perhaps on an ongoing basis—appraise the likelihood that a given individual will experience social success (this topic will be discussed in more detail later). It can be reasonably hypothesized that the designs of hypothetical adaptations underlying strategic cognition and behavior are quite openended, in which case their corresponding phenotypes might potentially underlie a wide range of routes to social success in one's local culture. To sketch a brief illustration of how such adaptations might conceivably develop and operate, we might imagine a young man whose psychological adaptations lead him to perhaps gradually realize that a range of routes to social success are unlikely for him. In which case, underlying psychological adaptations might accordingly increase the likelihood of him using aggression in strategic ways. For instance, such adaptations may compute that aggressively robbing someone of jewellery would increase his perceived status among peers and prospective mates, which might cause other adaptations to mentally rehearse various action schemata that might facilitate successful theft (e.g., Carruthers, 2015). Since psychological adaptations can be highly interconnected with one another, they can impinge on each other's computational operations, and in an iterative and complex, non-linear manner—in other words, they can feature in cycles of cognitive activity. For example, a psychological adaptation in men that computes one's ability to leverage their physicality in conflicts of interest (Sell, Tooby, & Cosmides, 2009)—by, among other things, assessing their own upper-body strength—could accordingly increase or decrease the likelihood of carrying out an assault, say, or (in keeping with the above example) attempting a violent theft. Another interesting question that can be posed in the context of an adaptationist understanding of aggression is whether men possess a psychological adaptation functionally-specialized for dealing with weapons. For instance, should such an adaptation exist, it may regulate, in part, when men use aggression (e.g., in which contexts) and how they respond to others either displaying weapons, known to possess them, or suspected of possessing them. The extent to which aggressive behavior might be learned from others should also be given consideration (e.g., Bandura, 1978; Mummendey, 1978). For instance, one might hypothesize that certain individuals who find themselves relatively disadvantaged—and therefore, from a Darwinian point of view, at a relative fitness disadvantage—might be more likely to pay close attention to others who act aggressively—and or feel motivated to seek out others with a reputation for toughness and aggression. To the extent that this may be true, individuals could attempt to learn how to think and act aggressively by observing and talking with other aggressive individuals (i.e., in order to imitate their aggression). It is also possible that aggressive behavior could be reinforced to the extent that it provides the individual with positive feedback. Wright (2017), for instance, offers a lucid discussion of how psychological adaptations can process events that are objectively harmful to one's fitness prospects as if they are actually beneficial to one's fitness prospects. For instance—and to use an example discussed by Wright—frequently consuming a large number of jelly donuts covered with powdered sugar appears to reliably get registered by one psychological adaptation or another as if one has consumed fruit, which we can assume was a healthy and fitness-conducing action in ancestral conditions. In so doing, the underlying psychological adaptation typically produces a positive affective response—that is to say, eating such donuts causes many people to feel good (at least those who like them or who have a predilection for sweet foods). Such feelings, produced by 33
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adaptations, tend to make people more likely to act in much the same way in the future. Yet, presumably the underlying adaptation registering the consumption of jelly donuts covered in powdered sugar as a boon to one's fitness prospects would continue to do so even if, objectively speaking—and perhaps also unbeknownst to the individual—eating them was actually making them less healthy, or putting them on a trajectory likely to lead to some kind of health complication later on. So, roughly speaking, psychological adaptations can sometimes register feedback as if it were a good thing—viz., as if it were beneficial to one's evolutionary fitness prospects—even when, in actuality—and particularly in a modern environment—it is harmful to one's evolutionary fitness prospects. And such a mismatch is, as noted, still likely to cause psychological adaptations to produce positive affective responses, which in turn make the behavior in question more likely in the future. Thus, to the extent that aggression receives positive feedback, it might make desisting from aggression even more difficult, at least in some individuals. This would be true even if aggression decreases one's actual fitness prospects in the current environment, and even if aggression is actually not in the interests of one's own wellbeing.
environment, should one exist. Roughly speaking, in social environments with an honor culture present, the psychological adaptation designed for reputation management develops and operates so as to be sensitive to the appropriate violations and slights to one's honor. To briefly illustrate the underlying logic of honor, we can consider a particular individual residing in a society or rural environment lacking the aforementioned institutional guards, and who also possesses a reputation for being extremely tough, belligerent, and willing to violently avenge transgressions and slights—such as theft attempts and verbal acts of disrespect. In which case—and all else equal—it would be expected that this particular individual would be less likely to be targeted in such a manner by other individuals, particularly other men, owing to their reputation for violent retribution. In addition, the honor of a man can affect his value both as a potential mate and alliance partner, with tarnished honor serving as an indicator of lower status and deficiencies in the various abilities valued in potential mates and allies, among other things. Furthermore, in anarchic-like conditions, we might expect there to be incentives to eagerly pounce on or otherwise manufacture opportunities to demonstrate and thereby broadcast a reputation for being tough, given its currency in such an environment. Ergo, it is possible that men possess a psychological adaptation for strategically utilizing violence in such an opportunistic manner (Winegard, Winegard, & Geary, 2014). For instance, according to the “Crazy Bastard Hypothesis”, men sometimes engage in behaviors that can serve to broadcast their toughness, or at least a reputation for being tough (Fessler, Tiokhin, Holbrook, Gervais, & Snyder, 2014). Finally, there is empirical evidence that honor cultures are at least partly sustained by cultural transmission occurring across generations—that is, from one generation to the next (e.g., Latzer, 2018). For example, one study found that professional hockey players raised in Canada were more likely to defend their honor by acting more aggressively during games (measured by penalty minutes) if they had been raised in towns that historically had been relatively distant from law enforcement officials (Restrepo, 2015). A natural explanation for why such players had elevated rates of aggression is that, historically, those born in such towns needed to rely more on defending their honor, since law enforcement was either less reliable or unavailable, owing to their relatively distant location in relation to those towns. Since the underlying psychological adaptation that governs honor culture and its associated aggressive tendencies served the function of increasing fitness in certain anarchic-like ancestral conditions, such an adaptation is likely to develop and operate whenever individuals find themselves in such conditions. However, given that such a psychological adaptation at least party relies on cultural transmission across generations as an important input, it appears that honor cultures can persist over time even long after they are no longer required (and no longer fitnessconducing). Thus, in the study of professional hockey players born in towns historically situated in places remote from law enforcement and courts, we can thereby explain why an honor culture has persisted among them, even though they were raised in such towns during a time when law enforcement and courts were present and reliable. For completeness, it should also be noted that processes of cultural transmission must ultimately be facilitated by underlying psychological adaptations as well (e.g., Sterelny, 2012). More generally, much empirical work remains to be done in order to illuminate all of the various functionally-specialized psychological adaptations that underlie various channels of cultural transmission and how those adaptations interface with other psychological adaptations in the mind (e.g., Tooby, 2014). It is also quite possible that those who are competitively disadvantaged and thus perceive poor prospects for social success will tend to be more likely to be receptive to honor cultures in the first place. Hence, this could explain differences between individuals living in the same locale, some of which find themselves embracing an honor culture, while others opt to eschew it (or find it less appealing, relatively speaking). In terms of the evolution of honor cultures, it may be helpful to think of culture as comprised of units of information—“memes”—that
5. Violence via honor A central motivator of violence across cultures is honor (Cohen, Nisbett, Bowdle, & Schwarz, 1996). Both empirical evidence and “agent-based” modeling show that honor is an evolutionary phenomenon that provides a fitness advantage to individuals (or would have done so under ancestral conditions), in that cultures of honor emerge in environments lacking the institutional guards that would otherwise provide safety from exploitation (Linquist, 2016; Nowak, Gelfand, Borkowski, Cohen, & Hernandez, 2016; Shackelford, 2005). So, from an evolutionary point of view, humans appear to possess a psychological adaptation for cultivating and defending their honor within particular ecological and cultural contexts, as well as for appraising the honor of others. Fundamentally, the honor of an individual can deter exploitation, and it is one's reputation for toughness which serves as the primary vehicle for communicating such information. Specifically, honor cultures are typically found in environments either lacking or deficient in policing—or some other adequate mechanism(s) by which individuals can be monitored—and where a form of dispute resolution (i.e., a justice system) is absent, unreliable, or otherwise corrupt. It is precisely under such conditions that individuals cannot rely on impartial third-parties to provide safety from and retribution for exploitation and physical harm. Indeed, under such conditions, impartial third-parties are either largely or entirely absent. Hence, absent these countervailing institutions and social arrangements, it becomes rational to cultivate and defend a reputation for being defiant in the face of infringements such as physical attacks, theft, or even verbal insults, etc.—in other words, it becomes rational to develop and guard one's honor. Indeed, even threats of such infringements can be sufficient grounds to elicit a defense of one's honor, whether by getting angered at the offending party and or violently attacking them. At root, within honor cultures, and all else equal, an individual will feel motivated to avenge any act that infringes upon their honor by responding angrily towards the perpetrator or attacking them outright—and particularly if the act and the retaliatory response are witnessed by observers, as witnesses also provide the retaliator with an audience with which to broadcast a message to (namely that the retaliator should not be exploited, derided, or otherwise slighted). So, defense of honor can indeed entail violent retribution directed at those infringing one's honor, which is often other men. This motive to avenge slights—which is underpinned by the appropriate psychological adaptation—is rational from the point of view of evolutionary fitness, since it acts as the proximate means by which one's honor is maintained. Shackelford (2005) has postulated the existence of a psychological adaptation designed for solving the problem of reputation management, which we can further postulate interfaces with an honor culture in one's social 34
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can evolve in the way that genes do. For our purposes, insofar as we're focusing on the adaptive nature of honor cultures, we can understand the units of information that comprise honor cultures as being selectedfor in environmental contexts within which they provided a fitness benefit (statistically speaking). Furthermore, defending one's honor can—and, at least ancestrally, likely regularly did—enhance one's inclusive fitness. For instance, to the degree that honor helped to safeguard one's resources and or increased their access to resources, a man's kin is also likely to benefit as a result; and any fitness benefits accrued by one's kin can count towards increasing one's inclusive fitness.
there are psychological adaptations determining the extent to which one is competitively advantaged or disadvantaged among one's peer group along the two broad domains of need and ability. For example, in societies with bridewealth and polygyny, men without mates (especially younger men) appear more likely to strategically use aggression to better their chances at attracting a mate (e.g., Hudson & Matfess, 2017), which can include participating in wars (to be discussed later). “Young bachelors who cannot afford to marry also make easy recruits for rebel armies. If they fight, they can loot, and with loot, they can wed” (M.B., 2018, para. 3). This observation is congruent with the view that certain men, owing to their disadvantaged relative-state—in this context, absent a mate and not well positioned to acquire one—will be more prone to behave in risky, aggressive ways. As such, proneness to risky aggression will flow from a relative disadvantage in both need and ability—namely, the absence of a mate and poor prospects for acquiring one, given the circumstances. Furthermore, we may hypothesize, for example, that needs for various markers of status, such as valuable objects, may be generated by an underlying psychological adaptation in relation to some appropriately circumscribed peer group. Such markers of status, should they be acquired, would help increase one's status, thus making them more appealing as alliance partners and, at least among men, more attractive to women (at least as long-term partners), especially relative to rivals. In contemporary societies, for example, luxury consumer items that effectively act as markers of status could hypothetically engender violent or non-violent theft among men whose underlying psychological adaptation appraises them as being competitively disadvantaged in relation to rivals who possess luxury consumer items. Plausibly, men who contemplate or engage in such theft might be driven to do so by underlying psychological adaptations that have computed their ability to obtain such markers of status in non-aggressive ways as, say, too difficult if not unlikely (to be discussed later). Underlying psychological adaptations might further compute an individual's ability to facilitate aggressive theft of valuable items as enhanced in some way, owing to relative advantages, or the surpassing of a certain threshold, in traits such as strength, endurance, and so forth. Since they can serve as a reliable signal of various qualities held by their possessor, the display or consumption of luxury goods can also be used to elevate one's status over others. In evolutionary biology, costly signaling occurs whenever an animal broadcasts a signal that is a reliable indicator of some underlying quality. For instance, if the intensity of a birdsong is reliably correlated with overall health because only those in very good health can produce intense birdsongs, then quality of birdsong can hypothetically serve as a reliable indicator of overall health. So, because only healthy animals can afford to produce such displays, those displays are therefore “costly signals” of that quality (in this case, health)—and costly signals are ipso facto reliable due their costs (Zahavi & Zahavi, 1999). Correspondingly, conspecifics can evolve a capacity to assess signals for properties such as reliability and quality. From a Darwinian point-of-view, luxury goods can give rise to competitive runaway processes, whereby individuals attempt to one-up each other in an iterated fashion (Frank, 2001; Miller, 2009). Hypothetically, then, men might be expected to be more prone to theft whenever such men lack the ability to acquire such luxury goods in a legal, non-aggressive manner, and so as to keep pace with rivals on that score, or to get ahead of them. In the mating domain, luxury goods might also serve as costly signals of the possessor's underlying qualities. For instance, luxury goods might serve as indicators of the financial status of the possessor, and or their general wherewithal to secure resources. Hence, potential mates might thereby assess a man's capacity to provision via his display of luxury goods. In addition, luxury goods might also hypothetically function to broadcast one's value as a potential ally if they are reliably correlated with traits and or properties that make one a valuable ally—for instance, if the possession of such
6. Relative-state, theft, and aggression Mishra, Barclay, and Sparks (2017) have developed an empirically supported, comprehensive framework for understanding the dynamics of risk-taking, which can serve as an evolutionarily-informed component of a Darwinian approach to explaining theft and gang membership (the latter of which will be discussed later). According to the “relativestate model” developed by Mishra et al. (2017), there are two pathways to risk-taking in general: one based on ability, and the other based on need. The ability-based pathway, to a first-approximation, reflects one's skills, talents, support from kin and alliances, monetary and material resources, and so forth. The ability-based pathway, moreover, can include features of one's somatic condition, such as health. The needbased pathway, to a first-approximation, reflects the various needs that an individual may appraise themselves as having, such as food, valuable objects, or mating partners (among many other possible needs). Fundamentally, one's relative-state is fundamentally a comparative issue: namely, the manner in which one compares to others in terms of abilities and needs. For instance, one's social competitors may possess status or access to valuable resources that one lacks, or one's social competitors may possess certain abilities that leave one comparatively disadvantaged. We may provisionally postulate that the relative-state model of risktaking captures the fundamental logic of whatever the psychological adaptations are that actually govern risk-taking among individuals. One benefit of having such a model is that it can serve as a useful research heuristic for identifying whatever the underlying adaptations are and mapping out their various design features—including which sorts of cognitive, bodily, and ecological variables they are sensitive to. In terms of needs, we may presume, for Darwinian reasons, that the mind contains psychological adaptations designed to deal with core needs such as acquiring food and obtaining a mate. However, given the open-endedness of many psychological adaptations and their complex interaction with one another, there will be various instrumental needs that get generated in service to core Darwinian needs. Furthermore, we should expect the range of possible instrumental needs to be very large and generated according to the designs of the appropriate psychological adaptations underlying them. According to the relative-state model (Mishra et al., 2017), risktaking is sensitive to the needs of particular individuals relative to others—for example, how an individual's access to a particular valuable resource compares to another person's access to that same resource. Relative to other individuals, the greater the disadvantage that one has in satisfying certain needs—viz., the more disadvantaged one's relative state is—the greater the likelihood that one will take risks. Risk-taking, furthermore, is also sensitive to the relative abilities of particular individuals. In the realm of needs, a Darwinian approach would suggest that the needs of men are partly shaped with reference to one's local peers, who ancestrally would have comprised one's reproductive rivals and potential allies. Thus, it would be worthwhile to better understand the psychological adaptations that compute (or the singular psychological adaptation that computes) who gets registered as one's reproductive rivals and who gets registered as one's potential allies (including how the two might overlap). Likewise, we may hypothesize that 35
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goods is correlated with valuable skills or knowledge (Plourde, 2008), social status, or traits such as strength.3 It is worth noting that evolutionary novelties such as money and luxury cars function as token representations instantiated in the phenotype of the psychological adaptation tasked with assessing which objects in one's ecology are valued and status-enhancing. A key upshot for our purposes, however, is that there are good reasons to expect there to be an underlying psychological adaptation that increases the likelihood that certain individuals—especially certain men—will, under certain conditions, engage in theft to obtain such markers of status. Other Darwinians have discussed the reasons why men have evolved a psychology that regulates risk-taking in a way that is sensitive to reproductive competition and one's standing in relation to peers in a number of crucial fitness-relevant domains (e.g., Daly, 2001; Mishra et al., 2017). It may also turn out that a low absolute level of abilities might suffice to explain why some individuals engage in aggressive theft. In such a case, we might expect underlying psychological adaptations to register a very low absolute level of abilities, which might be interpreted by the adaptation as a sign that low-risk strategies are—or were, ancestrally—unlikely to pay off in terms of social success. Accordingly, the psychological adaptation might increase the likelihood that the individual will engage in some form(s) of risk-taking, including theft. As an empirical hypothesis, therefore, it is worth testing whether chronic failure at achieving forms of social success in a legal manner is often sufficient to cause or increase the likelihood of theft, whether violent or non-violent. Such an investigation can also aim at ascertaining what cues the underlying psychological adaptation uses to compute chronic failure at achieving forms of social success in a legal manner—and whether there are specific thresholds, or whether the probability of such behavior is regulated in a way proportionate to the level and or frequency of failure. Similarly, it is also worth testing whether certain types of embodied and ecological parameters are attended to by underlying psychological adaptations as bellwethers of how likely nonaggressive strategies will garner social success for a particular individual. In which case, perhaps such parameters can be used as input into such adaptations for the purposes of impelling individuals towards more riskier, violence-prone social strategies. As per the risk-taking framework developed by Mishra et al. (2017), risk should be construed in a domain-specific rather than domaingeneral way (even though, among some individuals, it is often the case that risk-taking across various domains is correlated to some extent, and for reasons that the model can elegantly explain). Accordingly, risktaking is better viewed as arising not from a generalized propensity for risk, but rather as arising in a more specific manner, with individuals adjusting their risk-taking proclivities from domain-to-domain.4 For example, in domains where successful competition hinges heavily on strength, assessing that one is physically stronger than rivals would accordingly increase the likelihood that they would take risks in those domains, all else equal. For being stronger than one's rivals augurs well for being successful in those very domains (viz., where strength is an important factor for success). Hence, we may predict that men who are physically weaker will be less likely to engage in violent crimes, such as violent theft, whose successful execution depends in some substantial degree on physical strength, all else equal. Of relevance to this issue,
there is evidence of a psychological adaptation designed to compute an individual's strength (Sell, Tooby, & Cosmides, 2009) as well as the strength of others (Sell et al., 2009). Such assessments, therefore, can be used by other psychological adaptations implicated in computing the extent to which one should be disposed to deploying physical violence against certain individuals, in certain contexts. Equally, however, it is quite possible that possession of a weapon (and whether a potential target ostensibly possesses a weapon or is suspected of possessing one) can alter the computations of whatever the relevant psychological adaptations are that are implicated in aggressive theft, such that even relatively weak men will find aggressive theft to be a valuable option under such conditions (Fessler, Holbrook, & Snyder, 2012). Because ancestral humans probably generally gained reproductive fitness benefits from increased status (e.g., von Rueden et al., 2010; von Rueden & Jaeggi, 2016), it stands to reason that individuals—and men, in particular—would have evolved a psychological adaptation that allowed them to increase their status and or keep ahead of competitors via strategic risk-taking. Indeed, Ermer, Cosmides, and Tooby (2008) suggest the existence of a psychological adaptation that leads to riskybehavior among men in a functionally-specialized and context-sensitive manner. Specifically, and in line with their Darwinian-derived hypotheses, Ermer et al. (2008) found that men, but not women, are more likely to engage in risk-taking aimed at recouping a loss of resources—but not after gaining resources or after a loss of resources irrelevant to competition between men—and only when other men of equivalent status were observing them. These results suggest that the psychological adaptation governing risk-tasking in men is sensitive to status cues—specifically, cues that men of equal status are observing oneself. Such empirical results underscore men's sensitivity to relativestatus and lend support to the hypothesis that they have evolved an underlying psychological adaptation designed to be aware of one's relative-status and to deal with this reality in a fitness-conducing way. Indeed, such findings might lend credence to the earlier contention that violent risk-taking among men in service of acquiring luxury goods is closely connected to appraisals of relative status among reproductive competitors. In sum, aggressive risk-taking appears to be governed by underlying psychological adaptations sensitive to the ways in which one's needs and abilities compare to a reference class comprised by one's peers. Accordingly, some types of aggressive risk-taking might be explained by dint of individuals experiencing pressing needs, such as hunger, a need to maintain one's status among equal-status peers, or perhaps even sex, while other types of aggressive risk-taking will be more straightforwardly explained as a function of deficiencies or advantages in abilities, relative to some suitably circumscribed reference class of peers (Mishra et al., 2017). Fundamentally, however, it is plausible that much if not most aggressive risk-taking will occur among men for whom underlying psychological adaptations appraise as possessing abilities that make legal, non-violent routes to social success less likely if not effectively foreclosed—although, as will be discussed later, such appraisals need not be objectively accurate, as there is scope for error, especially in evolutionarily-novel environments. 7. Sex-ratios and predictive adaptive responses Another factor which may be significant for understanding aggression among men is sex-ratios, which at the very least appear to be correlated with violence (e.g., Barber, 2009b). However, even with respect to the correlation between sex-ratios and violence, some caveats are in order. Firstly, although it is often the case that an overabundance of males relative to females is often correlated with elevated rates of competitive risk-taking among males of various species, it appears as if the reverse is the case in humans (Schacht, Rauch, & Mulder, 2014; Schacht, Tharp, & Smith, 2016). In particular, an excess of women relative to men in a particular location is associated with elevated rates of violence among men. One interpretation of this pattern is that, when
3
In a related vein, Gambetta (2011) details the various ways in which signaling processes help facilitate organized crime. 4 It is worth pointing out that, in addition to helping to explain violent crimes, the framework of Mishra et al. (2017) can also help to explain “white collar” crime and non-criminal (or non-violent) forms of risk-taking, such as gambling and rock climbing. Although it might prima facie seem as if white collar crime is a maladaptive, unwise, and unnecessary form of risk-taking, its underlying rationale might make more sense when seen as a form of risk-taking stemming from the relative advantages of certain individuals, which in turn increases the likelihood of success at specific risky endeavors. 36
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women are the abundant sex, men stand to potentially benefit, from a fitness point-of-view, if they can secure more mating partners or mating opportunities via a more promiscuous mating strategy. Hence, under such a scenario, men appear to engage in more competition with one another, which could very well be tied to direct competition for mating opportunities with women (e.g., Griskevicius et al., 2009). Such competition might at least sometimes be used by women as a criterion for selecting short-term mating partners under conditions where they are the more abundant sex in a locale, or such competition between men might alternatively be used to neutralize the mating opportunities of rivals—which could thereby give competitively triumphant men better prospects for successfully courting mates (e.g., Puts, 2010). If deployed at least partially as a mate selection criterion, then, it is possible that women monitor aggressive competition between men and use it as an indicator of men's genotypic and or phenotypic quality (Gangestad, Simpson, Cousins, Garver-Apgar, & Christensen, 2004)—and or as an indicator of men's capacity to acquire resources (which would prove valuable should a woman form a long-term relationship with such men). Naturally, then, under conditions where competition between men is elevated, we could expect to see rates of violence between them elevated as well, which could explain the empirical association between violence on the one hand, and sex-ratios where women outnumber men on the other. In any case, it would be useful to model how an underlying psychological adaptation tracks the relevant sex-ratio in a given locale, and how such tracking feeds into other psychological adaptations in men that govern the propensity to engage in the kinds of risktaking that can lead to violence with other men. Empirical work by Schacht et al. (2014) is germane to this issue, as is their evolutionarilyinformed conceptualization of sex-ratios in humans. Another interesting observation of relevance here, noted by Schacht et al. (2016), is the feedback loop that incarceration can have on rates of violence between men.5 Specifically, in removing some number of reproductively active men from a given locale (at least for some time frame), incarceration is one factor that acts to alter sex-ratios, and can thereby even exacerbate sex-ratios that are already female-heavy, which in turn can increase aggressive competition between men even further, leading to elevated rates of violence. Once again, this is because of the increased mating competition that increasingly female-biased sex-ratios elicit—that is to say, the imbalance of more women relative to men tends to produce more potential mating opportunities for men, which at the same time incentivizes them to be more likely to forgo long-term commitment. Cultural norms and practices can also potentially affect rates of aggression. Socially penalizing promiscuity (e.g., Baumeister & Twenge, 2002), for instance, is a cultural norm that can regulate mating and, in so doing, significantly reduce mating competition even in contexts with sex-ratios where women outnumber men. And by dint of reducing mating competition significantly, a cultural norm that socially penalizes promiscuity can indirectly reduce aggressive competition among men. In addition, it is also plausible that female-heavy sex-ratios can contribute to violence in an additional, parallel manner via lowered rates of marriage (or lowered rates of stable pair-bonds). For instance, it is possible that male offspring being reared by single parents are, all else equal, disadvantaged in various ways relative to other offspring reared by intact families (that is, families with both parents present). Accordingly, since they might leave individuals competitively disadvantaged, it is possible that such developmental environments negatively affect an individual's relative-state in some ways, which could thus serve to increase the likelihood that they will ultimately deploy aggressive risk-taking as they mature. Empirically, family disruption is associated with rates of violent crime (e.g., Messner & Sampson, 1991). However, such a causal pathway should be investigated carefully, in particular with an eye towards evaluating it with, say, methods in
behavior genetics, which can control for the possible effects of genes, as heritable factors can confound an association between family disruption and increased levels of violent crime. At any rate, there is some evidence in behavior genetics—which controls for the potential confounding of heredity—that suggests that family disruption might ultimately negatively affect the relative-state of offspring (e.g., Burt, Barnes, McGue, & Iacono, 2008). In the realm of sexual competition, the psychological adaptation that underlies men's jealousy can, under certain conditions, lead to men exacting physical revenge on the men perceived to have had sex with their partners, whether real or imagined (and, no doubt, men can also exact physical revenge on their partners, and regardless of whether an act of cuckoldry is either real or imagined) (e.g., Buss & Shackelford, 1997). Of course, exacting such revenge on other men can lead to homicide as well. There are at least two naturally-selected rationales embodied by the psychological adaptation governing such acts (Buss, 2015). One rationale is to prevent a man's partner from cuckolding him in the first place, primarily by exercising vigilance over her. A second rationale is to maintain a man's honor among peers in the event that he has either been cuckolded or merely suspected of having been—the idea here, as with honor more generally, is that when others know or merely believe that a man has been cuckolded by his partner, but where he has also not acted to restore his honor, it broadcasts a signal that the man can be taken advantage of without reprisal. Recent work on “predictive adaptive responses” may also be relevant to understanding the evolutionary psychology of aggression among men. Predictive adaptive responses are hypothesized to be responses to particular variables, either within the organism or in the external environment, which occur during development (Nettle, Frankenhuis, & Rickard, 2013). As such, their naturally-selected designs can allow for organisms to develop in ways that would be adaptively optimal (at least under ancestral conditions) given the situation they find themselves in, whether ecologically and or in terms of physical and mental condition. One possible hypothesis in relation to male aggression pertains to the way in which the psychological adaptations underlying predictive adaptive responses might provide input into the psychological adaptation governing risk-taking. Specifically, it may be that particular inputs—for instance, very poor nutrition and or poor health—could function as input that causes the underlying psychological adaptation governing risk-taking to compute one's relative-state as disadvantaged (to some degree). Similarly, Frankenhuis and Panchanathan (2011) have discussed the ways in which psychological adaptations might be designed to “sample” environments for input on how to optimally develop. 8. Putting developmental trajectories and evolutionary mismatch in computational perspective Given the overarching theoretical model being developed in this paper, the understanding of aggressive risk-taking in terms of relativestate can be complemented by generating hypotheses about some of its other developmental and computational aspects. For instance, one hypothesis might examine the manner in which traits such as general intelligence and conscientiousness are processed by the underlying psychological adaptation that computes one's relative-state over time. Accordingly, one could, for instance, devise a variety of empirical tests that aim to look at whether variations in such traits in adolescents affect their aggressive risk-taking propensities—and if so, the particular domains to which such aggressive risk-taking is directed at. Many biosocial criminologists, for instance, would likely see these sorts of hypotheses as quite plausible, as they have frequently pointed out correlations between criminal and violent phenomena on the one hand, and traits such as intelligence (and scholastic achievement) on the other (e.g., Beaver et al., 2013; Schwartz et al., 2015). Taking this at face value, it may be that an underlying psychological adaptation computes one's abilities as it gradually receives various sorts of feedback
5 Similarly, incarceration rates, in altering sex-ratios, can reduce marriage rates (e.g., Charles & Luoh, 2010).
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throughout development, via interaction with the environment. In that case, an individual's underlying psychological adaptation might compute a disadvantaged relative-state of some magnitude when it consistently registers poor performance on certain kinds of tasks, and in comparison with peers—owing substantially, in this case, to lower levels of general intelligence. Such a process might operate in the context of modern societies when individuals low in general intelligence (and or conscientiousness) experience consistent negative feedback in the form of, say, failed tests at school, low school grades, etc., and where cues of one's poor standing relative to others are registered. Hypothetically, an individual need not even necessarily be fully cognizant of any of these cues so long as an underlying psychological adaptation detects and appropriately registers them. Once computed, the magnitude of the disadvantaged relative-state will then serve to regulate the individual's aggressive risk-proneness, although the manner in which that aggressive risk-proneness gets expressed might be specific to certain domains. Of course, the exact range of cues that such an adaptation would take in as input in determining one's relative-state at a given time is an empirical question. But in general, once such a disadvantaged relative-state was computed, it would influence the way in which the individual interacted with their environment such that opportunities for aggressive risktaking would be proportionally more likely to be sought after and capitalized on, all else equal. Empirical work by other evolutionary psychologists can also dovetail on these issues. For example, stronger men (as indexed by upper-body strength) have been found to be more likely to be assertive in contexts where there are conflicts of interest (Sell, Cosmides, et al., 2009; Sell, Tooby, & Cosmides, 2009). Sell, Cosmides, et al. (2009) and Sell, Tooby, and Cosmides (2009) argued that this phenomenon is governed by a psychological adaptation that assesses one's physical prowess and uses it as an input to compute an internal regulatory variable that governs behavior such as proneness to anger and feeling entitled to having conflicts of interest solved in one's favor. It is quite conceivable that such an internal regulatory variable that indexes physical prowess could influence where and when one engages in violence—for instance, the conditions under which one aggressively steals a valuable item, or whom one physically retaliates against in order to avenge a verbal derogation. In which case, the internal regulatory variable that indexes physical prowess would be available as input into the overarching psychological adaptation that governs aggressive risk-taking. More specifically, physical prowess can potentially be used as a relative advantage within broader contexts of relative disadvantage, as when an otherwise dim, poorly educated, impulsive individual uses their above average strength to overpower others in order to aggressively steal a valuable item or win a dominance competition of some kind. Interestingly, when specific relative disadvantages and specific relative advantages are juxtaposed against one another, it may be possible to predict or explain particular developmental paths taken by such individuals. For instance, in the case of especially strong individuals lacking in education, intelligence, and self-control, among other things, we might empirically predict that such individuals will be more likely to engage in more fights and be charged for violent crimes. In that sense, this particular suite of traits might be increasing the likelihood that such individuals follow certain kinds of lifestyles, the particularities of which are shaped and constrained by the ecological and cultural environment in which those individuals are embedded. If borne out empirically, such a prediction would support the adaptationist hypothesis that such individuals, probabilistically speaking, are utilizing one relative advantage—above average strength—to further their ends within the larger context of relative disadvantage, where they lack educational credentials, intelligence, self-control, and so forth. In sum, the precise developmental and computational design of the underlying psychological adaptations hypothesized in the foregoing must of course ultimately be mapped through much careful empirical investigation. This computational and developmental view of the
psychological adaptations underlying aggressive risk-taking will reemerge in our discussion of reactive heritability. At this point, it is worth reiterating the fact that the designs of psychological adaptations have been shaped by ancestral selection pressures. So, in the case of psychological adaptations underlying aggressive risk-taking, we should expect that their designs will not perfectly reflect the environments encountered in modern societies. In which case, this kind of evolutionary “mismatch” introduces one source of possible error when it comes to the ways in which psychological adaptations develop and function. For instance, the underlying psychological adaptations governing aggressive risk-taking might often lead individuals in modern societies to engage in criminal activities even if doing so is, in an objective sense, unnecessary to achieve a satisfactory level of social success (whatever that level and kind of success might be). Accordingly, the relative-state model of risk-taking can accommodate cases where individuals are inclined towards certain kinds of aggressive risk-taking even when a more objective assessment of their relevant abilities would suggest that such risk-taking is unnecessary and or overly rash—viz., more rash than the underlying adaptation “believes” it to be, since the adaptation's design reflects ancestral rather than modern environments. For since one's abilities are ultimately represented (i.e., instantiated) by an underlying psychological adaptation, the psychological adaptation might very well erroneously appraise an individual's prospects for social success. In which case, the underlying psychological adaptation could construe things “as if” the individual's abilities left them at a disadvantage in the pursuit of social success, whether that disadvantage was in absolute terms or relative to some reference class of social competitors. The upshot to this is that since psychological adaptations merely execute their underlying developmental designs, objective assessment can certainly be a mark that they miss in practice. Incidentally, being cognizant of the fact that psychological adaptations were naturally-selected in ancestral conditions can also help to partially illuminate why novel substances such as alcohol can affect cognition in a way that increases the likelihood of aggression (e.g., Pihl & Peterson, 1995). For, presumably, such psychological adaptations did not evolve under conditions where such substances (i.e., alcohol) were available. To further expatiate on some of the foregoing issues, we might hypothesize that men possess the capacity to make conscious, cognitive discriminations pertaining to whether to engage in aggressive behavior, desist from it, or avoid it altogether. For instance, it may turn out that the psychological adaptations that facilitate the rehearsal of action schemata interact with other psychological adaptations, and such that the latter adaptations bias the manner in which mental rehearsals are generated and evaluated. Furthermore, psychological adaptations can also operate in ways that are beneath the conscious awareness of individuals. This issue appears to be rather complex and rather tricky to arbitrate absent more empirical details. From the point of view of evolutionary psychology, a further complication arises from the fact that psychological adaptations are designed for past environments, not the present. So, all else equal, the capacity to objectively appraise current environmental contexts will be hampered to the extent that the design specifications and or phenotypic expressions of those adaptations are mismatched with the environmental contexts that an individual currently finds themselves within. For instance, since formal education is an evolutionary novelty for which our psychological adaptations are not adapted, when one is deliberating about one's educational prospects, one is engaging in deliberations for which one possesses no psychological adaptations specifically designed for that end—that is to say, we do not possess a psychological adaptation that was designed specifically for the function of thinking about one's educational prospects. Hence, all else equal, there would be greater scope for appraisal errors to be made by individuals, since the appraisal of one's educational prospects would be generated by the cognitive activity of psychological adaptations that are not designed for that end—such adaptations must instead be pressed in the service of making 38
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an appraisal of a situation that is very highly evolutionarily-novel. As a more general upshot, then, mismatches between the designs of psychological adaptations and the contemporary environments that they develop and operate in might make aggressive behavior more likely, even if, objectively, the fitness consequences for various individuals are likely to be worse as a result. Since aggression is by hypothesis taken to be generated by underlying psychological adaptations designed by natural selection to be deployed in certain contexts so as to enhance one's fitness prospects, there is no guarantee that those adaptations will function to that end in modern environments—at least to the degree that those modern environments diverge from the past environments that shaped the adaptations implicated in aggression. To illustrate the foregoing, however, we might imagine a particular scenario in a modern environment in which one's psychological adaptations bias them towards an aggressive action, but where the aggressive action objectively stands a very slim chance of actually increasing that individual's reproductive fitness. However, counterfactually, it may be that the same kind of aggressive action would have stood a higher likelihood of increasing one's fitness prospects ancestrally. Whereas the latter (ancestral) scenario might ultimately garner the individual an increase in status which they then parlay into enhanced reproductive fitness, the former (modern) scenario might lead to a prison sentence and no enhancement of reproductive fitness. In this pair of contrasting hypothetical scenarios, the key difference that makes the difference, roughly speaking, would be the mismatch that exists between the environment and relevant psychological adaptations in one scenario but not the other. Aside from various sorts of mismatch between psychological adaptations and contemporary environments, however, we might expect that aggressive risk-taking generally and accurately reflects one's abilities, and generally and accurately reflects actual advantages and disadvantages in relative-state. But it is quite possible for an appropriate psychological adaptation to erroneously assess which avenues for social success are objectively open to an individual. Accordingly, such a psychological adaptation might simply be unaware of avenues for nonaggressive, legal social success that are in principle available to a given individual. One interesting corollary to this is that certain inclinations towards aggressive risk-taking in at least some individuals might be dampened or perhaps eliminated if the underlying psychological adaptations become “convinced”—by whatever means—that non-aggressive, legal avenues for social success could be effectively traversed. Similarly, individuals could be introduced to ways of gaining status that they were previously unaware of. For instance, perhaps a young man who might otherwise be prone to violent crime, owing to certain disadvantages in abilities, and against the backdrop of currently perceived options for gaining status, can be convinced that, say, broadcasting his singing or acting abilities on social media would grant him the peer esteem that he desires (e.g., Patterson Jr, 2015). Similarly, perhaps an individual otherwise prone to violent crime could be convinced that there were educational opportunities of some kind available to them which could lead to some form of social success that they desire. Empirical tests of these ideas could be conducted, and hypothetical policies could be developed that, for instance, offer aggression-prone individuals options for escaping dangerous living conditions and pursuing newly discovered avenues for social success. Apropos to the topic of reducing aggression, neighborhood residents and (i.e., non-profit) organizations might potentially exert various positive effects on a local community, such that it can have meliorative effects on crime prevalence in that community (e.g., Sharkey, Torrats-Espinosa, & Takyar, 2017). More generally, the adaptationist model developed in this paper is also compatible with the idea that individuals—including, for our purposes, men—can be dissuaded from considering aggressive risktaking and violent crime as an option by, for instance, reconsidering the manner in which they narratively construe their life (e.g., Peterson, 2002). To this end, Ward and Fortune (2013) discuss a rehabilitation program dubbed the “Good Lives Model”, which, among other things,
aims at helping individuals develop skills and acquire various kinds of supports that could assist them in attaining the kinds of social success that they desire. Moreover, it is quite possible that many men in possession of a disadvantaged relative-state might be more likely to refrain from attempting to gain status through violent means if they were to simulate mating success through the use of prostitutes or sexbots—doing so would, in other words, provide “fake” fitness cues to underlying psychological adaptations, hence satisfy mating drives and thereby curtail if not obviate the drive to use aggression in the first place (Fleischman, 2018). It is possible that the effortless and regular access to sex that prostitutes and sexbots can allow for can provide the psychological adaptations of men with feedback that mimics the cues of actual reproductive success. In other words, it is possible that prostitutes and sexbots might provide the psychological adaptations of men with input that is processed as if they have successfully mated. Prima facie, though, it may seem that this hypothesis is in tension, if not direct contradiction, with the empirical observation that a surfeit of women relative to men in a local mating market is correlated with elevated levels of male aggression. Perhaps this apparent incongruity can be resolved by hypothesizing that the mating competition between men for access to those surplus women becomes more intense, which in turn increases the likelihood of violent confrontations, whereas prostitutes and sexbots might simply circumvent that intense mating competition altogether, or often enough. Hence, effortless and regular access to prostitutes and or sexbots might remove the kind of competition between men that might otherwise be liable to turn violent whenever women outnumber men in a local mating market. In any case, these hypotheses require a good deal of further empirical investigation in order for them to be adequately tested. In light of the considerations raised in this section, clinicians might therefore find some use in evolutionary approaches to understanding male aggression. For example, they may find that it helps in identifying young men who might perceive their prospects for social success to be uncertain—uncertain because such young men perceive themselves to be disadvantaged in some way, relative to their peer group. Of course, according to evolutionary approaches, the ways that people perceive and can come to understand social success will typically mirror the recurrent, fitness-relevant concerns of the evolutionary past—i.e., climbing status hierarchies; being liked or admired by others; finding a mate; etc. But, as should be clear from the approach developed in this paper, there are idiosyncratic aspects to the ways that individuals perceive and come to understand their own prospects for social success. Thus, clinicians working with aggressive individuals might find the evolutionary approach heuristically usefully in that it can help them identify routes to social success that are reasonably within reach of their clients, either now or with some effort. Just as importantly, it can help clinicians identify which of those paths their clients are also likely to see as attainable, meaningful, and as gaining them status. The potential heuristic value that the evolutionary approach can have for clinicians, therefore, has two broad aspects. On the one hand, it helps them zero in on the space of attainable and meaningful non-aggressive alternatives for achieving social success that their clients can pursue. And on the other hand, it allows clinicians to devise this course in a way that makes them sensitive to the idiosyncrasies of their clients that are relevant to devising such an alternative path through life. 9. A Darwinian perspective on war and gangs From a Darwinian perspective, war and the existence of gangs are perhaps unsurprising. For example, among our closest evolutionary cousins, Chimpanzees, troops will sometimes gradually and systematically kill off male members of a rival troop that wander alone near a shared territorial border (e.g., Wrangham & Glowacki, 2012). Indeed, this phenomenon mirrors the coalitional violence seen in our own species. Normally, chimpanzees from one group will attack a member of 39
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a rival troop when that member has been separated from their own troop—for instance, when a lone chimp has wandered to the border separating the territories of two respective troops. Chimps also appear to be more prone to attack other chimps when the attacking coalition is larger than the coalition being attacked, suggesting that they evolved an adaptation designed to track the relative-sizes of coalitions in realtime (Wrangham & Glowacki, 2012). Interestingly, there is also evidence that, when in the presence of other members in their own coalition, humans see solitary individuals from rival coalitions as physically smaller and less muscular, which suggests a parallel between humans and chimps so far as coalitional cognition is concerned (Fessler & Holbrook, 2013). Humans have indeed seemingly evolved a coalitional psychology designed for tackling the multifarious problems of living within and among coalitions—whether those coalitions are friendly, neutral, or hostile (e.g., Kurzban, Tooby, & Cosmides, 2001; Moya & Boyd, 2016; Tooby & Cosmides, 2010; Voorspoels, Bartlema, & Vanpaemel, 2014). Our overarching psychological adaptation for living in coalitions often also fuses our identity with those very coalitions, and to varying degrees (Swann Jr, Gómez, Seyle, Morales, & Huici, 2009; Swann Jr, Jetten, Gómez, Whitehouse, & Bastian, 2012). And fusing one's identity with a given coalition is at once a mechanism that strongly binds them to a group and raises the probability that, at least under certain conditions, one will experience strong enmity of rival groups, particularly if those rival groups are perceived as infringing on the welfare of one's group (e.g., Tooby & Cosmides, 2010). Various evolutionists have argued that humans evolved psychological and cultural adaptations for waging war with other groups (as well as peaceful relations with them) (e.g., Gat, 2009, 2015; Glowacki et al., 2017; Pitman, 2011).6 Such a view squares with archaeological, ethnographic, and historical evidence. Supplemental to this (as already mentioned) is evidence that humans have evolved a psychological adaptation for living in coalitions, and, on the flip side, dealing with other coalitions, at least some of which are likely to be rivals. At any rate, assuming that humans have adaptations that evolved for war, they are highly sensitive to many factors and hence do not ineluctably impel humans to be warlike, much less to actually engage in war. A key question, however, is that given that raids and battles against rival groups are intrinsically quite risky for even those individuals comprising the attacking coalition, why would men have evolved to participate in such attacks in the first place? Another question closely related to this one is why such motives for participating in war would have evolved in the first place, given that, over evolutionary history, individual men could have simply let other men in their groups do the risky attacking and then simply shared in the spoils of war. However, given elementary evolutionary considerations, if such spoils of war were distributed evenly or randomly to men in a given group irrespective of their participation in such wars, then the psychological adaptation underlying the propensity to participate in war would have been purged by natural selection. Specifically, the psychological adaptation underlying war would have been removed owing to the fact that participators would have had lower evolutionary fitness than their free-riding peers. Since this all seems paradoxical given the evidence that exists in support of psychological and cultural adaptations for war, it suggests that the above questions must have answers—that such prima facie problems were in fact solved by natural selection. Indeed, it has been argued that men do possess various motivations for war, and by which, crucially, they can derive fitness benefits. Specifically, men can often gain increased status within their coalitions through their participation in war—and especially for acting in ways
considered valuable and brave by their coalitions, including war heroism (Glowacki & Wrangham, 2013; Rusch, Leunissen, & van Vugt, 2015). And such status can of course lead to reproductive success, either directly through access to more and or better quality mates, or indirectly through, for instance, deference from others, more and or better allies, and so forth (e.g., von Rueden et al., 2010). Furthermore, other sources of possible benefits include capturing women from rival groups, and or stealing valuable items. Hence, in spite of the serious risks to life and limb, the psychological adaptation underlying war can, under the right sorts of conditions, galvanize men to participate in battles and raids, and so on. From an ancestral point-of-view, it is also plausible that groups came to blows over animal game, since the latter are likely to have moved across the landscape in such a way that disregarded any established territory that groups may have claimed for themselves (e.g., Gat, 2015). And, given that animal game was such a limited and crucially valuable resource throughout human evolution, there would have been ample incentive to at least sometimes disregard territorial boundaries, or at least compete with other groups for such animal game. Thus, there was more than enough room for tensions between groups to build up over access to such a prized resource. It is worth noting, however, that there are various reasons why participation in war might be compelled rather than because individuals derive benefits from their participation—for instance, there can be cultural institutions in place within a group that enforce punishment on those who fail to participate, or who fail to participate adequately, in war activities (Mathew & Boyd, 2011; Zefferman & Mathew, 2015). With regard to war and gangs, there is also scope for understanding their cultural aspects in terms of cultural group selection (e.g., Turchin, 2007, 2010; Turchin, Currie, Turner, & Gavrilets, 2013). For instance, when groups aggressively compete with one another with some frequency, cultural differences between those groups can, all else equal, make one more likely to ultimately prevail over the others. All else equal, then, certain cultures—or certain cultural beliefs, cultural values, or cultural practices—make for more aggressively formidable groups. For instance, in discussing the role of warfare in the rise of empires within the context of cultural group selection (or multi-level selection), Turchin (2007) notes the observation of the medieval historian Ibn Khaldun, who argued that certain cultures possessed greater levels of trust and cohesion—what he referred to with the Arab word “asabiyyah”—and which made them more effective in battle. Indeed, as Turchin (2007) argues, war can facilitate cultural evolution and, ultimately, the selection of certain cultural groups over others. It is perfectly reasonable, therefore, to examine the degree to which the various cultures of gangs and warring tribes have been shaped by processes of cultural group selection: namely, the degree to which aspects of their cultures have been selected-for (via the natural selection of units of cultural information) within the context of aggressive competition between those cultural groups. For instance, one might imagine the cultures of two warring tribes—or two gangs—coming to valorize ferocity more and more, and such that one tribe's culture comes to valorize ferocity even more as a result of the other tribe's culture elevating their own valorization of ferocity. Thus, both cultures can feedback on each other and thereby mutually increase their respective cultures' valorization of ferocity—they can, in order words, become enveloped by a ferocity spiral. And this kind of cultural evolution can even occur without any particular individuals consciously intending to change their culture in this manner (Dennett, 2017). Recent work on the “male warrior hypothesis” (McDonald, Navarrete, & Van Vugt, 2012) can also help shed light on some of the other aspects of evolved male psychology that might contribute to gang phenomena. Briefly stated, however, a core part of the male warrior hypothesis contends that men have evolved an inclination, under certain conditions, to join coalitions with other men and engage in conflict with other coalitions so as to gain access to fitness-enhancing resources, such as territory, food, and women. For example, for men whose relative-state is especially disadvantaged, joining a gang will often be a
6
The discussion of war in this section does not aim at explaining the unique aspects of warfare at or above the so-called “military horizon”. The focus of this section, rather, is warfare beneath the military horizon, which, as Pinker (2011) puts it, pertains to “the raids, ambushes, skirmishes, turf battles, feuds, and depredations that historians dismiss as ‘primitive’ warfare” (p. 199). 40
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tempting option, even if some or many men realize the inherent dangers of doing so. Simply put, since such men are disadvantaged in the pursuit of social success, gangs can offer the opportunity of gaining the status and resources that are otherwise difficult for them to obtain. Hence, an individual with low relative-state may find themselves especially receptive to coalitions (i.e., gangs) that market themselves in ways that are attractive to those looking for a path to life success—i.e., status and mating opportunities. For instance, this same sort of path to a violent lifestyle is not entirely dissimilar to the manner in which some men are attracted to the messaging of coalitions animated by violent jihad (Atran, 2010; McCauley & Moskalenko, 2010; Taşpınar, 2009). Whether a street gang or extremist organization, such coalitions appeal, whether explicitly or implicitly, to central Darwinian motives of men, particularly a desire for status and mating opportunities (e.g., Thayer & Hudson, 2010). Alternatively (or in conjunction with the above), such coalitions might offer an enticing opportunity for individuals with needs that are difficult for them to meet in non-violent ways, such as to satisfy drug addictions. Furthermore, the existence of local gangs can also present individuals with the threat of being exploited and physically harmed (e.g., O'Flaherty & Sethi, 2010). So, given the fact that gangs can simultaneously be a source of opportunity and threat for certain individuals, there will often be ample incentives for them to join one. A Darwinian understanding of gangs can also underscore the need for adequate policing to help curb the conditions that can help generate them in the first place. Most straightforwardly, Hobbesian-like conditions of anarchy that conduce to gang formation are most likely to be found in pre-state societies and failed states (Wrangham & Wilson, 2004). For under such conditions, there is no “Leviathan”—no overarching authority and policing mechanism—that can oversee the security of individuals, impartially enforce rules, and mete out punishment for violations of such rules. Likewise, once one gang has formed in a given location, it simultaneously creates a pressure for non-members to either join it or join together in a gang of their own, if for no other reason than to provide themselves with protection against that gang. In addition, honor can function at the level of coalitions—in this case, at the level of gangs. For instance, one gang might be widely perceived as “weak”—in particular, less likely or capable to defend against and avenge attacks and poaching. Under such conditions, and all else equal, we might expect that particular gang to more frequently be targeted by rival gangs, or to proactively attempt to elevate their honor. The dynamics of honor at the level of gangs can also spiral out of control, as when two or more gangs get caught in continual cycles of attack and counter-attack, which can quickly slide into a perpetual state of conflict between rival gangs. In such a case, all parties also have an incentive to stand their proverbial ground and maintain a reputation for toughness—that is to say, as a gang that is to be reckoned with and not taken advantage of or otherwise disrespected. In addition, individual gang members might also be incentivized, one way or another, to raise their rank within their gang by stealing from, physically attacking, or outright killing a member of a rival gang, all of which can add even more fuel to the fire of hostilities between gangs. From an evolutionary point of view, such actions can signal to fellow gang members that one has a variety of useful, valuable qualities that they bring to the gang and that they are committed to it, all of which increases their status within the gang and can even showcase their capacity to function in a leadership position (e.g., Donovan, 2012; Van Vugt, 2006). And, of course, petty disputes between members of rival gangs can also give rise to acts of violence, such as assault and homicide. Likewise—and to take one example—violent conflict between gangs can be sustained when they battle for hegemony over drug dealing in a local area. In sum, although gangs caught in the midst of such a destructive dynamic would objectively be better off if they could manage an armistice or sustained peace, insofar as the context in which their interactions occur is characterized by anarchic-like conditions, it will be difficult to interrupt their mutual hostilities. For without strong third-
party institutions to intervene and provide security or justice (i.e., police and courts), there is less incentive to cease their reciprocal and incessant violent antagonisms, all else equal. At root, and according to an evolutionary perspective on honor as it functions at the level of gangs, one of the central engines fueling such hostilities is a reputation for honor—a reputation that gangs seek to maintain and broadcast. 10. The evolutionary genetics and heritability of aggression A number of biosocial criminologists have attempted to illuminate aggression (as well as crime and delinquency more generally) in terms of its heritability. Here, my aim will be twofold: First, to bridge behavior genetics with the explanatory model developed in this paper, and then to briefly discuss the evolutionary processes that can act to generate heritable variation in traits connected to male aggression. Heritable variation in violent crime has been established by behavior geneticists (e.g., Barnes et al., 2014; DiLalla & Gheyara, 2011; Ferguson, 2010; Rhee & Waldman, 2002).7 On the one hand, these studies show us how much of the variance in a given population, at a given time, can be explained by heritable factors. Yet on the other hand, heritability studies are largely silent on the mechanistic and developmental details that subserve the heritability of traits. In order to see how these two sides of the coin are interrelated, we can start by considering the concept of reactive heritability, which sketches how heritable traits express or magnify themselves developmentally (e.g., Tooby & Cosmides, 1990; von Rueden, Lukaszewski, & Gurven, 2015). To illustrate how such processes can work, we can consider an example germane to aggression, whereby an individual inherits above average physical strength. From the figurative point-of-view of the underlying psychological adaptations that govern aggression (broadly speaking), and all else equal, it is unknown what the level of physical strength is in the organism that the adaptations are developing and operating in. However, it is possible that natural-selection can design such adaptations so that they can assess what the agent's physical strength level is—perhaps, for instance, by attending to feedback regarding how often, and to what degree, the agent is either successful or unsuccessful in physical conflicts of interest with other agents. Given these assessments, the underlying psychological adaptation can then compute an overall index of the agent's physical strength, and then utilize that index when judging if and when to instrumentally mete out aggression. Whether such an adaptation has actually evolved, and, if so, what its design features are, are of course empirical questions. However, evolutionary psychologists have indeed found experimental evidence that suggests that a psychological adaptation has evolved in men that can assess one's physical strength, and then use that assessment as an “internal regulatory variable” which governs, for instance, one's proneness to use anger as a bargaining tactic during conflicts of interest with other agents (Sell, Cosmides, et al., 2009; Sell, Tooby, & Cosmides, 2009). Similarly, one possible route through which lower levels of general intelligence—which is also quite heritable as a trait (e.g., Bouchard Jr, 2004; Bouchard & McGue, 2003; Plomin & Deary, 2015; Sniekers et al., 2017)—might in some cases give rise to violent crime, at least in contemporary environments, is via the feedback that those in possession of low cognitive ability receive. For example, and as discussed earlier, since cognitive ability is a strong predictor of academic success and educational attainment, low cognitive ability thereby places a constraint (at least to some degree) on what one can achieve in this regard. Accordingly, and else equal, one's economic prospects will hence be likewise constrained, since cognitive ability is a significant factor (albeit certainly not the only factor) that, on average, increases one's 7 Heritability measures are measures of variance in particular traits in certain populations at a given time. In principle, heritability measures can be different for different populations and they can change when causally relevant aspects of the environment change.
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economic prospects, at least in modern societies (e.g., Murray, 2013)—and so inheriting low cognitive ability is more likely to lead to poorer educational attainment, which in turn constrains one's economic prospects. And as outlined earlier in this paper, appraisals of which avenues for social success are available to a given agent, whether explicit or implicit (or a combination of both), can interact with processes such as the one just sketched. Thus, one can imagine circumstances in which certain individuals, for whatever reasons, think and feel that their prospects for social success are limited, which, in addition, can be exacerbated by low levels of general intelligence (at least in circumstances where low general intelligence limits one's educational prospects). So, in cases where one's relevant psychological adaptations have computed one's prospects for social success as poor, and as partly informed by developmental processes that interact with heritable traits such as general intelligence and conscientiousness, the psychological adaptations that underlie instrumental aggression, for example, may hence be more likely to impel the agent to aggressive, violent crime, at least in certain contexts. Similarly, this same trajectory might also raise the likelihood that an individual will consider joining a gang or other forms of organized crime, since those options might provide some prospects for social success that are otherwise assessed to be less likely. Recall, again, that heritability studies, though quite illuminating and very interesting in their own right, do not necessarily disclose much about the ways that heritable traits manifest themselves mechanistically (including througout development). Apart from processes of reactive heritability, a second way in which heritable variation in traits can manifest themselves is in a more direct fashion, namely by leading to developmental changes in the brain, oftentimes very early in ontogeny. For example, this more direct pathway manifests when a certain allele (gene variant) is shown to reliably cause a specific difference to some aspect of the brain and its functioning, typically very early in ontogeny. It is also important to point out that reactive heritability and the more direct manifestations of heritability—via more directly observable influences on the structure and functioning of the brain—are not necessarily mutually exclusive. So while it is possible in principle that either type of manifestation could account for some or even much of the heritable variance in traits related to aggression, it is quite possible that both kinds of processes are involved. For instance, one process might explain some traits while the other process explains other traits; or some or many traits might be explained by some combination of both processes: that is, certain traits might take on a certain form for congenital reasons very early in ontogeny and then be modified via the process of reactive heritability during development. Furthermore, a given trait might be flexibly calibrated over development in some individuals via reactive heritability and or responses to phenotypic and environmental factors, while perhaps being set by congenital factors in other individuals via direct genetic effects on the brain—and so a given trait might be affected by either such pathway in different individuals (e.g., Glenn, Kurzban, & Raine, 2011). Additionally, processes of reactive heritability, presuming they exist, can combine their effects with adaptations that respond in flexible ways to phenotypic and environmental contingencies. Hence, a given trait might be calibrated to an extent by a process of reactive heritability—whereby, say, a regulatory variable gets computed over the course of development by a psychological adaptation functionally-specialized to do so in response to certain heritable traits—which then is calibrated further—upwards or downwards—depending on other factors, such as, for example, one's relative-state, which itself can be at least partly influenced by heritable traits. In any case, and once again, the precise details must obviously be ascertained empirically. Importantly, however, the variance in aggression (or violent crime more generally) that can be accounted for by congenital damage, such as deficits in prefrontal cortex, might turn out to be quite high (e.g., Raine, Stoddard, Bihrle, & Buchsbaum, 1998). Thus, this possibility should serve to make us cognizant of the fact that certain aspects of the evolutionary model being developed in this paper might in the last analysis only be able to account for a modest amount
of male aggression once causes such as brain lesions and congenital factors such as brain abnormalities are accounted for. A separate question to the above pertains to the evolutionary source of heritable variation itself, and regardless of how such variation manifests mechanistically and developmentally. The two main types of evolutionary processes of relevance to this question are balancing-selection and mutation–selection balance. One form of balancing-selection occurs when more than one allele (i.e., gene variant) is maintained within a given gene pool owing to the fact that each of those alleles possesses equal fitness effects, on average. This can occur when each allele provides fitness benefits in certain spatial environments, or when each allele provides fitness benefits at certain times. For instance, an allele that gives rise to a certain kind of coloration in an organism could prove fitness-enhancing in certain patches within an ecological niche, but not in other patches, and an allele that causes an organism to forage for longer periods of time (relative to other organisms in possession of a different allele) could prove fitness-enhancing during certain generations, but not during others. Each of these sorts of fitness benefits, therefore, can maintain the corresponding alleles in the gene pool, since the fitness costs of a particular allele, whether at given spatial locations or temporal durations, are balanced by fitness benefits at other particular spatial locations or temporal durations. One possibility hereabouts is that alleles that underlie a propensity for aggression have been accordingly selected-for in the past, and are now found at certain frequencies within populations. For example, it is possible that certain alleles, such as the 2-repeat allele of the MAOA gene (e.g., Beaver, Wright, et al., 2013)—the so-called “warrior gene”—have been naturally-selected through the process of balancing-selection because they provided a fitness benefit to their bearers, on average. A second form of balancing-selection can occur when the fitness of a given allele is contingent on its prevalence within a particular population, otherwise known as frequency-dependent selection. For instance, certain alleles that underlie psychopathy might have been maintained at certain frequencies within certain populations because, at those given frequencies, psychopathy was—and perhaps still is—a social strategy that paid off in terms of fitness (e.g., da Silva, Rijo, & Salekin, 2015; Glenn et al., 2011; Mealey, 1995; Međedović, Petrović, Želeskov-Đorić, & Savić, 2017). However, if this kind of scenario can account for at least some of the heritable variance in psychopathy, it is likely that the underlying alleles are kept in balance through frequencydependent selection, which is a manifestation of balancing-selection that, in this case, would reduce the frequency of the underlying alleles when and if they exceeded a certain frequency. The idea here is that psychopathy, as a manipulative and predatory social strategy, was over some stretch of evolutionary time fitness-conducing, on average, but only insofar as, for instance, psychopaths did not encounter other psychopaths—which is a scenario that would have likely proved to be especially fitness-diminishing. The higher the frequency of the underlying alleles, however, the more likely they will be to encounter one another, all else equal. Hence, frequency-dependent selection can act to reduce the frequencies of such alleles once they rise above a certain level, thereby keeping those gene variants fit (that is, fitness-conducing) within a given population. At any rate, with regard to balancing-selection, it remains an open question whether some or much of the heritable variation in aggression—via traits such as psychopathy, for example—has been maintained over evolutionary time because aggression provided a fitness advantage in certain contexts. The other main type of evolutionary process that can maintain heritable variation, mutation–selection balance, occurs whenever the rate of harmful, fitness-reducing mutation outstrips to some degree the rate at which selection is able to remove such mutations from a given gene pool (e.g., Keller, 2008; Keller & Miller, 2006). In general, the number and effects of mutations vary between individuals, with each individual carrying an overall “mutation load” that has gradually accumulated over the generations of one's lineage. It is possible that much of an individual's relative-state and absolute state can be illuminated 42
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through the lens of mutation–selection balance, as the overall mutation load possessed by an individual can act to handicap them in various ways with regard to the traits that contribute to social success in general (whether in contemporary or ancestral environments). It is possible, for instance, that mutations can affect a trait like general intelligence (e.g., Yeo, Gangestad, Liu, Calhoun, & Hutchison, 2011). In which case, to the extent that general intelligence is connected to male aggression, the underlying heritable variation in male aggression will owe its source at least to some degree to mutation-selection balance, since it contributes to heritable variation in general intelligence. As another example, differences in self-control can explain some proportion of variation in male aggression (e.g., Moffitt et al., 2011). And some proportion of the variation in self-control, being heritable, perhaps owes some of its source to underlying mutations and is hence maintained by mutation–selection balance. In general, it remains to be seen how much of the heritable variation in male aggression can be explained by mutation–selection balance, and via which traits in particular it disrupts the functioning of.
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