Evolutionary theory in public health and the public health of evolutionary theory

Futures 43 (2011) 762–770

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Evolutionary theory in public health and the public health of evolutionary theory Daniel J. Kruger * School of Public Health, University of Michigan, 1420 Washington Heights, Ann Arbor, MI 48109-2029, United States

A R T I C L E I N F O

A B S T R A C T

Article history: Available online 24 May 2011

Evolutionary theory is the most powerful explanatory system in the life sciences and is the only framework that can unify knowledge in otherwise disparate fields of research. Considerable advances have been made in the application of evolutionary biology to health issues in recent decades. Health researchers and practitioners could benefit considerably from an understanding of the basic principles of evolution and how humans have been shaped by natural and sexual selection, even if they are not explicitly testing evolutionary hypotheses. Life History Theory is a powerful framework that can be used for examining modern human environments and developing environments that maximize opportunities for positive health outcomes. Many of the recommendations derived from this framework converge with the visions of current public health advocates. Despite the benefits of an evolutionary framework, the challenges that face those attempting to integrate evolutionary theory into public health are perhaps greater than those in the social sciences. Although considerable advancements in the understanding of health issues have already been made, health researchers with an evolutionary perspective are very few in number and face constraining disciplinary attributes. Advances in medical technology will continue to extend the boundaries of saving lives in danger, however traditional public health efforts may be reaching their limits of effectiveness in encouraging health-promoting behaviors. This may partially account for the current interest in broad social and policy change to enhance health and reduce health disparities amongst sub-populations. Such substantial physical and social restructuring will face many challenges and gradual progress may be enhanced by a strong foundation of evolutionary human science. The slow but eventual integration of evolutionary principles will gradually enhance the effectiveness of health interventions and provide an ultimate explanation for patterns in health outcomes that are otherwise puzzling. The speed at which the field of public health adopts a Darwinian framework has yet to be determined, and several futures are possible. This pace will depend on several factors, including the visible utility of evolutionary theory for addressing the health promotion goals of the field. ß 2011 Elsevier Ltd. All rights reserved.

1. Introduction Evolution by natural and sexual selection is the most powerful theoretical framework in the life sciences. As Dobzhansky famously wrote, ‘‘Nothing in biology makes sense except in the light of evolution’’ [13]. Evolution by selection is not just an

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explanation for the diversity of life and its myriad biological mechanisms; it is also the only comprehensive theoretical framework that connects the various levels of biological study, from biochemistry to ecology. This framework holds the promise of consilience amongst the sciences, providing a scaffolding to unite findings from widely divergent methodologies [65]. Darwinian medicine is an emerging perspective in the health sciences and there is great potential to extend beyond clinical applications and advance the structure of our entire health system. Evolutionary theory provides some counterintuitive insights on health issues. Some symptoms of disease are actually protective mechanisms, and attempts to alleviate these symptoms might prolong and/or intensify illness [43]. These days, most people take the power of antibiotics for granted [64]. Insecticides and antibiotics have saved many lives, but they have also created a co-evolutionary arms race between quickly evolving organisms and applied scientists. We are now seeing destabilization in infectious disease patterns with the rise of antimicrobial resistance [39]. To elongate the duration of effectiveness of anti-parasitic agents, we may need to use these resources strategically and even shift the focus of efforts away from eradication and towards management [50]. Our immune systems are adapted for a higher parasite load than we typically experience in modern environments. When raised in an overly sterile environment, our immune systems may start reacting to seemingly innocuous antigens, triggering allergies. Children who grow up with frequent exposure to animals, such as pets and livestock, have lower rates of hay fever and asthma [58]. Chron’s disease occurs when the immune system attacks the gastrointestinal tract; it appears to be the result of a defense mechanism that was useful for a much higher parasite load. Based on this insight, cases of Chron’s disease have been successfully treated with ova from pig whipworms, which divert the immunological defenses towards a naturalistic target [60]. Evolution is most often slow, being the result of selection across many generations. We have dramatically changed our environment in the past ten thousand years, beginning with settlements and agriculture and continuing through the Information Age. The pace of these changes has accelerated since the Industrial Revolution [22]. We seek fats, salts, and sweets in our diet because these provide valuable and necessary energy, however they were scarce in our ancestral environment [15] and are now much easier to obtain today than they were even two hundred years ago. Food production consumed considerably more energy amongst our ancestors [37]. We exercise far less on average today, especially in automobile-centric cultures such as the USA. Modern public health and scientific medicine have dramatically reduced some of the main causes of death amongst our ancestors, such as infectious diseases [39]. Unhealthy lifestyles are a major contributor to the most prevalent causes of mortality today, including cardiovascular diseases, cancer, and diabetes [7]. High survival rates and weak selection pressure in modern environments will not enable adaptation to the rapid environmental changes occurring within generations. The best way to address modern health issues may be to change our environment so that health-promoting behaviors arise from the natural course of daily activities. Selection is constrained as there are limits on what will evolve based on the systems already in place, and the adaptiveness of intermediate forms. Every trait is a trade off; there will be conflicts of interest because of pleiotropic genes. Because fitness consequences are non-identical even between mothers and their offspring, they can also experience conflicts of interest [63]. Genetic imprinting on an offspring’s genes may partially mediate some of the most common prenatal disorders, including gestational diabetes, fetal growth restriction, preeclampsia, and miscarriage [20,40,41,51]. One of the fundamental insights of the evolutionary perspective is that organisms are shaped for reproductive success, not for health or longevity. This insight applies to our physiology as well as psychology. We discount future consequences and seek thrills, sometimes through relatively safe cultural creations such as roller coasters and horror movies, sometimes through more hazardous activities such as extreme sports and street drag racing. Males are usually more susceptible to risk taking, especially as adolescents and young adults, leading to substantially higher mortality rates from behavioral causes [31]. Our evolved psychology creates constraints for the effectiveness of health education-people will not always do what would be in their best long-term health interests. As stated previously, a large proportion of morbidity and mortality in modern populations stems from unhealthy lifestyles and modern environments. This does not imply that the solution to these ills is to return to or attempt to broadly replicate Pleistocene conditions. The hominid ancestral environment was considerably more dangerous than that of today, and life expectancy was much shorter and mortality rates were considerably higher across the lifespan. The environments of evolutionary adaptedness (EEA) are really a statistical amalgam of selection pressures that reach back millions of years, perhaps as far back as the origin of life itself. There was no Garden of Eden or single ideal environment that humans were perfectly adapted to. Life History Theory (LHT) is a powerful framework that can be used to understand variation in behavioral and physiological strategies as functional adaptations to environmental conditions. This framework may be extended to an examination of modern human environments as related to health issues and the development of environments that maximize opportunities for positive health outcomes, as discussed below. Behavioral and physiological strategies reflect tradeoffs in the allocation of effort towards specific aspects of survival and reproduction across the lifespan [52,59]. Because the total amount of effort is limited, organisms face tradeoffs between different possible forms of investment. In the early stages of an organisms’ life, the somatic effort of building and maintaining one’s body takes precedence over reproduction. Once an organism reaches sexual maturity, a greater portion of the organisms’ resources becomes devoted to reproduction. In addition to mating effort, humans exhibit very high levels of parental investment, which is proportionally higher than in many other mammalian species. Organisms must also make tradeoffs between current and future reproduction, and between the quantity of offspring produced and the amount

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invested in each offspring. These inherent tradeoffs in allocation of investment are influenced by the environmental conditions in which organisms live. Individual physiological and behavioral strategies generally reflect adaptations to developmental conditions [52,59]. The original models of LHT predicted that species living in environments with resource instability and unpredictability of future events (high extrinsic mortality due to predation, for example) will tend to evolve clusters of traits associated with rapid reproduction, risky behavioral strategies, and relatively low investment in offspring [36,47]. In contrast, species living in stable and predictable environments are expected to instead have a long-term strategy, investing more so in their offspring as well as in their own physiological well-being. Species living in resource instable and unpredictable environments are said to be ‘‘r-selected’’ (r is the growth rate of the population), species living in more stable and predictable environments are said to be ‘‘K-selected’’ (K is the carrying capacity of the population). The terms fast and slow life histories are also used, respectively, especially when describing individual differences within species. Individual differences in life history within species are contingent on environmental conditions and thus LHT can be useful in understanding the causes of human individual differences in behavioral strategies and physiological functioning [53]. Although the heritability of life history strategies is evident, the degree to which these strategies are implemented in humans is likely shaped by environmental circumstances such as socio-economic, cultural, and ecological conditions, and physical constraints [23]. Theorists and previous research suggest that individuals developing in relatively less certain environments will exhibit riskier, present oriented, behavioral strategies because of the low probability of reproductive success for more cautious approaches. For example, neighborhood homicide rates are predicted by neighborhood life expectancy (controlling for the impact of homicide) and neighborhood income inequality [67]. People who had shorter lifespan estimates and higher estimates of the unpredictability of the future had a higher frequency of risk-taking [24]. Those living in chronically risky and uncertain environments are more likely to experience earlier menarche, earlier ages of reproduction, and higher reproductive rates [8,16,26,28]. Paternal investment in offspring is inversely related to pathogen load, as parental effort would be lower in environments where parenting cannot improve offspring survival [49]. In these environments, male strategies shift towards relatively higher levels of mating effort with greater risk taking. Public health professionals may associate characteristics of slow, or highly-K selected life history strategies as good or desirable. People who are relatively higher in K selected characteristics have more stable relationships, greater investment in their children, lower levels of risk taking, and may be more community oriented. In contrast, those who exhibit lower levels of K selected characteristics are more impulsive and have a greater disregard for social rules [17]. These individuals have a greater focus on short-term gains at the expense of long-term costs, at the individual and perhaps even the societal level. We should be careful to realize that in evolutionary terms, neither relatively fast nor relatively slow life history strategies, whether across or within species, are inherently ‘‘good’’ or ‘‘bad,’’ as a range of strategies have proven successful given the appropriate environmental conditions. As a species, all humans are strongly K-selected [35], so individual variation will typically occur towards the K end of the continuum. Convergent with LHT, the field of Behavioral Ecology follows the principle that behavioral strategies related to reproductive success are conditional based on the characteristics of the physical, economic, and social environment [10]. Our theoretical framework provides an understanding of why behavioral patterns arise, rather than a moral or ethical evaluation. Recommendations following from LHT are predicated on the valuation of low mortality rates, high life expectancy, lower levels of behavioral risk taking, stable parental relationships, high investment in children, and high degrees of helping and social support amongst kin and neighbors as desirable outcomes. Also, rather than being seen as an account of individuals fulfilling some genetically determined destiny, LHT offers guidance in how to generate environments that will encourage cautious, long-term strategies that engender healthy lifestyles (see the section below). The value of LHT models for health promotion stem from the explicit recognition of phenotypic flexibility rather than genetic determinism. So what does the future hold for the integration of evolutionary theory into public health? There is an increasing recognition of evolutionary influences on the heightened risk taking behaviors of young males, for example [42]. The American College of Epidemiology’s 2008 conference was themed ‘‘The Dawn of Darwinian Epidemiology’’. Hopefully this will prove to be an accurate description, but it could also be a brief flash of light, and before long, some other issue will capture the attention of the field. The future possibilities range from an enthusiastic and complete integration of evolutionary theory to complete and utter rejection of its applicability in public health. The eventual reality is likely to fall somewhere in-between. 2. Evolutionary theory becomes the foundation of public health Because of its sheer power and scope, the evolutionary framework is increasingly adopted as the foundation of understanding in the human sciences. This foundation makes it increasingly apparent that the health sciences (along with the other human sciences) are really complementary aspects that converge in a larger empirically driven account of humanity. Researchers exploring a wide range of topics with a vast array of techniques will not only report their esoteric findings, but will also provide the broader context in which the findings may be interpreted, to facilitate integration into the larger body of scientific knowledge. The evolutionary perspective will grow from a special interest area within each discipline into an organizing principle that pervades every corner of every field. Researchers will become de facto evolutionists even when their focus is on the minutiae of very specific phenomena.

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Public health professionals will appreciate that the implications of evolutionary insights converge nicely with recommendations for social conditions that facilitate health, yet provide a deeper understanding of the causal framework behind social and health patterns. Population health improvements in the past 150 years have generally been from social, economic, and environmental changes, and future improvements are also likely to stem from these factors [21,39]. Sustainable health improvements will entail a negotiation between individual freedoms and large-scale social change for the public good [64]. Disciplinary and departmental boundaries will blur, as students are able to transfer knowledge to other areas with increasing ease. All introductory courses will be explicitly evolutionary, as this will facilitate the understanding necessary for increasing specialization. Journals will require authors to address evolutionary implications. Academic and professional societies will enter into federations to promote dialogue based on interest areas, rather than levels and methods of analyses. The unified theoretical foundation will accelerate the progress of the scientific understanding of humans and their world, to reach the limits of available research technology. 3. Public health rejects evolutionary theory Much of the previous forecast may eventually come to fruition, although it is likely to occur over the course of several academic generations. Evolutionists may be especially aware of the challenges and limitations in promoting even the most powerful theoretical approach. Human nature constrains scientific progress both in the mental limitations of individuals and social dynamics of the production of knowledge. Academic discourse, whether in presentations and debates or peer reviewed articles and books, does not create some sort of group mind that automatically adopts the ideas which best account for the given evidence. The selection pressures in our ancestral environments have shaped the capabilities of our minds. Sub-atomic physics is far less intuitive to us than the movements of the much larger projectiles that may also help or harm us. Our mind evolved to perceive only objects and events that are in the natural range of human experience [12]. The value of quantum theory is negligible when one only has access to Stone Age (or even early 20th Century) technology. It is also difficult for many to accept that the apparent design seen in complex organisms is the product of millions of iterations of selection on a chemical code. Such an understanding is far removed from the types of knowledge that helped our ancestors find shelter, forage for food, and protect themselves from predators and hostile hominids. We have tendencies to infer agency and intentional causality where there is none because many of our higher cognitive abilities evolved to aid us in social situations [3]. Even amongst academics, there will be those who may accept biological evolution as an explanation for our physiology, but not the mental capacities generated by our evolved physiology. There are other challenges to the adoption of the evolutionary perspective that are general across sectors of research. There is a healthy skepticism of theories that claim to be dramatic advancements on currently held beliefs. We should not expect something so radical to be easily adopted. Researchers may be threatened by new approaches that claim to be advances on current practices. Of course many researchers and scholars consider themselves to be seekers of Truth, but they are also embedded in career tracks and multiple social hierarchies. There is competition for the upper echelon of academic positions, within departments and across institutions. Although knowledge is often assumed to be cumulative, many see the mechanics of producing knowledge as a zero sum game, where the success of one’s competitors detract from one’s own standing. Finding a niche and exploiting it to the fullest, sometimes generating many manuscripts with minimally publishable differences establishes research careers. Any change that may create a deviation from this process or its acceptability may be seen as a threat. There are also disciplinary issues specific to or more relevant for public health that may slow the process of evolutionary integration. The sciences largely focus on theory building and hypothesis testing; the goal is advancing knowledge and understanding. Even in the applied area of Clinical Psychology, the dominant Boulder Model advocates the theme of clinicians as scientist–practitioners. Public health is largely an applied profession, most of the actual work in the field focuses on health education, service delivery, geographically or sub-population specific trends in health issues, and intervention. The types of career roles are even more diverse in public health than in Psychology, and the proportion of the field in academic or other basic research settings is much smaller. For those working outside of academic settings, there may be a perception that evolutionary theory yields little or no practical implications [54]. Some public health practices explicitly follow psychological models, such as the Theory of Planned Behavior [18]. There are also implicit assumptions about human psychology and behavior embedded in much of the public health framework, which tend towards the tabula rasa school of thought regarding the human mind. Also, in Psychology the focus is on the individual, the current center of attention in public health is the influence of socio-economic factors. These factors are known as the social determinants of health [9], a label that reflects beliefs of causality in the contemporary perspective of the field. Of course, the work of public health is also much more focused on direct benefits to individuals and society than most psychological research. The goal is the improvement of health and the elimination of inequalities in health outcomes across groups. Public health is also much more political than psychology, in the ‘‘big P’’ sense. Many of those working in the field have an explicit or implicit ideology, which may be informed by work related experiences of adverse health outcomes. There is strong interest in changing public policy across a wide range of issues, not just those specifically related to health care. Ideological constraints may slow considerations of evidence for evolutionary theory. The ‘‘baby boomer’’ generation that now dominates

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in academic positions of power in the USA is certainly not homogeneous, however many of these academics were shaped by experiences of historical events in ways that influence academic discourse. The generations that were raised during, and participated in, the civil rights era of the 1950s and 1960s may be particularly idealistic and sensitive regarding social equality. Any explanation that recognized individual differences not caused by the social structure could be perceived to undermine quasi-Marxist worldviews [57]. This may be especially true for those in public health, a field with a strong focus on helping others. Public health workers may be self-selecting in both the intention to do good works as well as the relatively lower value placed on the pursuit of social status and material wealth, compared to peers who pursued more lucrative professions. Health researchers and practitioners may be especially wary of the application of evolutionary theory to their field because they may associate this with the eugenics movements of the early 20th Century. Sociobiology was perceived to advocate racism, eugenics, and genocide simply because it suggested that human behavior could be genetically influenced, rather than being solely determined by socialization and culture [56]. Inspired by eminent public figures such as H.G. Wells, John Maynard Keynes, and W.K. Kellogg (whose eponymous foundation funds many public health projects today), eugenics programs ranged from family planning and prenatal care programs for mothers to forced sterilization and state laws banning interracial marriage. After the revelation that Nazi officials justified euthanasia and genocide with their interpretation of eugenics principles, eugenics fell out of favor. Despite this, forced sterilizations continued in the USA through the early 1980s [25]. It is very important to understand the distinction between modern evolutionary research and the selective breeding programs promoted in previous eras of human history. Modern biologists recognize that there is no teleology in evolution; no person or people are more highly evolved than any other persons or peoples. Everyone alive today is descended from a very long line of successful ancestors. Simultaneously, some health disparities may partially be a result of differential selection pressures on ancestral populations. Humans have colonized nearly every land area on the surface of the earth, and each of these diverse ecologies shaped the genotype of ancestral populations. For example, the genes that cause sickle cell anemia when homozygous, was likely selected for because of the advantage to heterozygous individuals in resisting malaria [33]. Certain alleles may cause or exacerbate health problems when expressed in modern environments. Although genes for lactose tolerance evolved independently in several human populations that domesticated livestock [62], the likelihood of lactose tolerance differs by ancestry. Those who are lactose intolerant have a greater susceptibility to environmental lead poisoning due to lower levels of calcium [4]. 4. Evolutionary theory is incorporated into specific aspects of public health Neither extreme is the most likely future scenario. We will probably have some degree of evolutionary integration, the extent and speed to which this occurs has yet to be determined. Some areas of public health may be more immediately receptive than others, based on the perceived relevance of evolutionary theory to the specific theory or practice. Some prospective areas are covered below, these include the traditionally domains of public health practice as well as domains which reflect an understanding of the factors important to mental and physical well being. 4.1. Nutrition Some researchers recommend a Paleolithic diet of lean meat, fish, fruits, vegetables, root vegetables, eggs, nuts and lower levels of sodium. This diet contrasts with the grains, dairy products, refined sugar, fats, and oils that constitute most of the calories in contemporary Western societies. Proponents have found the Paleolithic diet to prevent obesity, digestive problems, heart disease, stroke and some forms of cancer [34]. These recommendations are based on the notion that the human genotype has changed little in the past 10,000 years, and our digestive system has not adequately adapted to changes in diet since the Pleistocene [15]. More recently, genetic studies have shown that the rate of human evolution has increased since Homo sapiens began leaving Africa 40,000 years ago, and since agriculture emerged 10,000 years ago, the rate of genetic change has accelerated to 100 times those of historical levels [24]. Rising populations created more opportunities for beneficial mutations to spread, and environmental changes in ecology, disease, and diet likely created selection pressures. The independent origin and spread of adult lactose tolerance in European, South Asian, and East African populations demonstrates a nutritional advantage for those who can consume dairy products beyond infancy [24]. Migration away from the equator selected for mutated genetic alleles that influence salt homeostasis, alleles that also play a role in the metabolism of environmental carcinogens and prescription drugs [61]. Further research will be needed to identify optimal diets, which may be contingent on one’s ancestral heritage. Human cultures exhibit a wide range of diets, although the modern food surplus is an anomaly for the vast majority of the population. 4.2. Health psychology and health education In the next decade, we are likely to see a greater fusion of health psychology with the insights provided by an understanding of evolutionary selection pressures. These insights will not only include the ultimate explanation for why people do not always act in their best long term health interests, but will also improve the effectiveness of health education

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efforts through the recognition of motivations and concerns emerging from ancestral selection pressures. Scholars of health futures appreciate the need for attention to people’s motivations and preferences [21]. For example, framing sun exposure in terms of perceived aging of skin for women and linking smoking to erectile dysfunction in men may be more effective than messages framed around increased mortality risk [56]. Interventions that take advantage of evolved psychological mechanisms may address men’s desires to gain and maintain social status and women’s relatively greater concerns for physical attractiveness. Parents may be motivated to follow actions framed as facilitating the success of their children, and grandparents may be motivated by messages related to generativity and social connection. Our psychological time horizons may be unsuitably brief for maintaining health behaviors whose benefits are not seen in the short term. The high mortality rates and unpredictability of ancestral environments have left us with a penchant for future discounting. It may be useful to build in an incentive structure that rewards people in the short-term for maintaining exercise and weight goals. In addition to rewards for beneficial behaviors, we can also make unhealthy behaviors more immediately costly. For example, increasing taxes on automotive fuels and creating-built environments that facilitate walking and other non-motorized transportation will promote exercise and possibly greater levels of social interaction. Indulgence taxes on junk foods could mimic high taxes on tobacco products. Artificially intelligent companions may be able to provide guidance when navigating health risks and monitoring health behaviors [2], but must be implemented carefully lest they become nagging nuisances as satirized in the dystopian film Demolition Man. 4.3. The health consequences of social status gradients Socio-economic inequality is one of the factors influencing health outcomes [38]. There are likely many mechanisms underlying this relationship, including lack of access to health services and residence in less affluent neighborhoods amongst those with lower socio-economic status. The relationship between social position and health is even stronger for men than it is for women [31,32,38,55]. This is because wealth and social status is related to male reproductive success and mating competition across human history and societies [26,35]. Because men are more likely to be evaluated on their achieved social position [6,30], men have stronger tendencies for risk-taking and competitiveness in the service of social advancement, and a greater sensitivity to hierarchy [11]. This creates a paradox, for despite the substantial evidence on the adverse health impact of social status inequality, especially on men, there will be substantial political opposition to redistributions of wealth or resource control, especially from men. Men are both more sensitive to their position in the social hierarchy as well as to perceived threats to their relative status. The fragility of socialist utopias such as the Paris Commune of 1871 and other intentional communities without status differentials indicates the difficulty of sustainably implementing such social structures. Modern states that are nominally socialist or communist are in fact totalitarian. Evolutionary biologist Edward O. Wilson once remarked that ‘‘Karl Marx was right, socialism works, it is just that he had the wrong species’’ [44]. Wilson of course was referring to the true eusocial insect species, where one female specializes in reproduction and the haplodiploid reproductive system gives other females an incentive for working together to raise their sisters rather than reproducing themselves. Our solutions must be within the possible range of human adaptation; otherwise they will fail. We have norms of reaction that are influenced by environmental factors, but our phenotypes are not completely plastic. It may be impossible to eliminate all status differentials, however relatively egalitarian foraging societies exist and may serve as a model for providing equality of opportunity. 4.4. Naturalizing the built environment Research on environmental influences on health initially focused on the negative effects of hazardous agents such as toxic chemicals and radioactivity [19]. More recently there has been greater recognition of the health promoting aspects of naturalistic environments. Our health may benefit from natural settings and constructed environments which extensively incorporate natural features. We appear to have an affinity for the natural settings of our ancestral past, preferences that developed over millions of years of evolution [66]. Landscapes with features necessary for survival and sustenance; fresh running water, plants and non-human animals, defensible space, moderately dense forestation, all promote physical and mental health [19]. This phenomenon encourages efforts to create more green space in urban and suburban environments and incorporate naturalistic features into our buildings such as open running water and extensive vegetation. Architects and landscape planners such as Fredric Law Olmstead have recognized the importance of naturalistic elements for well being, showing an inherent understanding of human biophilia [66]. In the next decade, there will be increasing numbers of currently existing projects such as community gardens, which provide locally produced fresh produce, better air quality, and additional public green space. Such projects will increasingly take advantage of both horizontal and vertical urban space. Vertical space in urban areas is a largely untapped resource for growing vegetation, and multiple stories increase the potential arable space beyond the building’s footprint. Other integrations of the natural environment, from green rooftops to biking and walking paths, will further erode the Brutalist concrete jungle often featured in the past half century of urban construction. Modernist architects vilified decoration and ornamentation and found inspiration in mass production industrial processes such as Henry Ford’s assembly line [1]. The modernists created buildings and landscapes with smooth walls, simple forms, plain drab colors, and large areas of glass. So called ‘‘urban renewal’’ programs demolished historic structures

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with more elegant designs and replaced them with endless derivative copies of modernist works by lesser-known architects. Developers were likely thrilled with the lower costs associated with bland, mass produced modernist inspired structures. Minoru Yamasaki, of World Trade Center fame, designed the Pruitt Igoeflats public housing development in St. Louis following the principles of the great modernists. The development was so well regarded amongst Yamasaki’s peers that it won an American Institute of Architects prize. By 1972, just 17 years after their construction, the Pruitt Igoeflats had a higher crime rate and had been defaced to a greater degree than any other public housing development and were eventually demolished [45]. Later architects have recognized the fundamental problem of modernist architecture – they conflict with people’s natural preferences and even make the inhabitants uncomfortable and angry. Mies van der Rohe’s expectation that tenants in his buildings would keep their blinds at the same height so that the buildings appeared properly ordered [45] shows the disconnect between modernist architects’ visions and the needs of the residents. Perhaps this is why such modernist architecture is featured so prominently in Stanley Kubrick’s cinematic adaptation of Anthony Burgess’ dystopian A Clockwork Orange. 4.5. Restructuring the human environment to promote health Those in public health are very aware of the current obesity epidemic and other recently emerging health challenges that stem in part from the structure of modern human environments. Health promotion education efforts have certainly yielded benefits, yet after several decades of health education many health indicators in the USA are stagnant or declining. Perhaps this is one of the factors underlying the strong interest in policy change, seen as a theme in several recent public health conferences. This poses an opportunity for policy advocacy with a basis in evolutionary science. Health advocates will be pleased to know that many such recommendations converge with their own current efforts. Those residing European cities and North American locations such as Manhattan enjoy advantages including comprehensive public transportation, more substantial public open spaces and parks, and easily accessible produce and grocery stores, restaurants, shops, and public services. Exercise rates are higher when individuals can access nearly all necessities through a combination of walking, biking, and public transportation. In the USA there has been gradual ‘‘gentrification’’ of urban areas in the past four decades, as educated young professionals have placed greater value on proximity to recreational and cultural opportunities, as well as shorter commutes. The market pressure for densely populated urban areas with abundant social and cultural assets will likely increase. Gas prices in the USA rose above $4/gal in 2008, providing hints of what will happen in the next two decades as fuel prices rise, steadily or not. Sociologists are predicting the decline of exurbs and outer suburban commuting communities, as transportation costs rise. In the next quarter century, changes will be more dramatic, coinciding with the advancing development of the energy and transportation infrastructures. Residential neighborhoods will increasingly become pedestrianized areas and biking and jogging paths will connect auto-free zones with minimal barriers. Greater investment in public urban schools will help reduce the population flow to the suburbs when children approach school age. A LHT framework provides a scientific basis for broader structural changes. Individuals who have experienced environments in which personal safety, social support, and resource control are uncertain may be more likely to discount future outcomes in favor of present ones. Others who experienced more reliably supportive environments where resource control is more certain could be expected to exhibit the reverse pattern as a reflection of experiences that promote longerterm strategies. By facilitating stable access to necessary resources and high perceptions of safety and community cohesion, perceptions that current effort will pay off in the future will be enhanced, and longer-term strategies will emerge. The creation and extension of public, safe, family friendly social space would help decrease levels of interpersonal crime and increase perceptions of safety. The architectural properties of defensible space and local recreation and socialization opportunities would contribute to social capital and cohesion. Social isolation is related to morbidity and mortality, with an increased degree of risk comparable to tobacco smoking [5,27]. Although the human social environment is changing due to the possibilities of Internet communication, changes in the built environment will also have a social impact. Urban residential space may be dense, but it need not be anonymous. Structurally defined neighborhoods or community units with limited access points and shared social space could facilitate socialization for groups of 100–200 individuals. It is estimated that a group size of around 150 was most common throughout most of human history, due to cognitive limitations in information processing for social networks [14]. 4.6. Global ecology and long-term biosphere sustainability Evolutionary insights include the recognition of the need for social as well as ecological sustainability. The ecological consequences of the high resource demands of our consumerist culture along with rapidly expanding populations is creating the greatest ecological collapse since the Cretaceous – Tertiary boundary event 65 million years ago [29,46]. Considerably more resource and energy conservation, as well was population stabilization, will be necessary for humans to develop a sustainable relationship with their environment as well as ensure their own healthy future [21]. The histories of projects such as Biosphere 2 demonstrate the difficulties of creating sustainable ecologies from scratch [48]. An evolutionary understanding of the inter-dependence of species, including human dependence on the global ecosystem, may encourage conservation efforts and facilitate the radical technological and cultural change needed to ensure our survival as a species [66].

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5. Conclusion Evolutionary theory offers a powerful framework for understanding the patterns of causality in complex health phenomena. Our health status results from traits shaped by natural selection interacting with environmental and cultural variations, giving rise to complex patterns that would be difficult to explain with a non-evolutionary framework. An evolutionary perspective offers an integrative and comprehensive causal framework for understanding health phenomena of great theoretical interest as well as practical importance. A generation from now, evolutionists will have created a stable academic niche for enthusiasts and a greater degree of understanding and respect from the field as a whole. However, evolutionary hypotheses will likely be tested by a selfselected subset of scholars within the field. Most researchers will continue to follow their own non-evolutionary research interests, as they do today, and may only address the evolutionary implications of their work when writing the discussion sections of their manuscripts. We may be currently experiencing the apogee of social constructionism in the health sciences, and the theoretical pendulum will swing towards a multi-level causal framework with an evolutionary foundation in future generations. Public policy will increasingly be informed by science, and health policy will be informed by the most powerful theory in the life sciences. The evolutionary framework will not only advise on how to address a problem, but also how to identify the problems that need to be addressed. If public health is to continue advancing as a science, this integration will be inevitable. The results will include social and physical environments that facilitate positive health outcomes across every sector of society. Dramatic changes are not likely to be seen in the next five years, but the seeds have already been sown. We are likely to see a gradually increasing interest in the evolutionary framework, and this interest will grow in proportion to the benefits which evolutionary theory brings not just to theoretical advancement, but perhaps more importantly, in the effectiveness of health promotion and disease prevention programs and interventions. References [1] R. Best, Beyond modernism, in: R. Best, G. Valence (Eds.), Building in Value: Pre-Design Issues, Arnold, London, 1999, pp. 11–19. [2] A. Bostrom, Future risk communication, Futures 35 (2003) 553–573. [3] P. Boyer, Natural epistemology or evolved metaphysics? Developmental evidence for early-developed, intuitive, category-specific, incomplete, and stubborn metaphysical presumptions, Philosophical Psychology 13 (2000) 277–297. [4] K. Bruening, F.W. Kemp, N. Simone, Y. Holding, D.B. Louria, J.D. Bogden, Dietary calcium intakes of urban children at risk of lead poisoning, Environmental Health Perspectives 107 (1999) 431–435. [5] B.H. Brummett, J.C. Barefoot, I.C. Siegler, N.E. Clapp-Channing, B.L. Lytle, H.B. Bosworth, R.B. Williams, D.B. Mark, Characteristics of socially isolated patients with coronary artery disease who are at elevated risk for mortality, Psychosomatic Medicine 63 (2001) 267–272. [6] D.M. Buss, The Evolution of Desire: Strategies of Human Mating, Basic Books, New York, 1994. [7] Centers for Disease Control and Prevention, Chronic diseases and their risk factors: the nation’s leading causes of death, Author, Atlanta, GA, 1999. [8] J.S. Chisholm, Death, Hope and Sex: Steps to an Evolutionary Ecology of Mind and Morality, Cambridge University Press, Cambridge, 1999. [9] Commission on Social Determinants of Health, Closing the Gap in a Generation: Health Equity Through Action on the Social Determinants of Health, World Health Organization, Geneva, 2008. [10] C. Crawford, J. Anderson, Sociobiology: an environmentalist discipline? American Psychologist 44 (1989) 1449–1460. [11] H. Cronin, The Ant and the Peacock: Altruism and Sexual Selection from Darwin to Today, Cambridge University Press, New York, 1991. [12] R. Dawkins, The God Delusion, Bantam Press, New York, 2006. [13] T. Dobzhansky, Nothing in biology makes sense except in the light of evolution, American Biology Teacher 35 (1973) 125–129. [14] R.I.M. Dunbar, Neocortex size as a constraint on group size in primates, Journal of Human Evolution 20 (1992) 469–493. [15] S.B. Eaton, S.B. Eaton III, M.J. Konner, Paleolithic nutrition revisited: a twelve-year retrospective on its nature and implications, European Journal of Clinical Nutrition 51 (1997) 207–216. [16] B.J. Ellis, J.E. Bates, K.A. Dodge, D.M. Fergusson, L.J. Horwood, G.S. Pettit, L. Woodward, Does father absence place daughters at special risk for early sexual activity and teenage pregnancy? Child Development 74 (2003) 801–821. [17] A.J. Figueredo, G. Va´squez, B.H. Brumbach, S.M. Schneider, J.A. Sefcek, I.R. Tal, D. Hill, C.J. Wenner, J.W. Jacobs, Consilience and life history theory: from genes to brain to reproductive strategy, Developmental Review 26 (2006) 243–275. [18] S.A. Fila, C. Smith, Applying the theory of planned behavior to healthy eating behaviors in urban native American youth, International Journal of Behavioral Nutrition and Physical Activity 3 (2006) 11. [19] H.S. Frumkin, Beyond toxicity: human health and the natural environment, American Journal of Preventive Medicine 20 (2001) 234–240. [20] J.A. Graves, Genomic imprinting, development and disease – is preeclampsia caused by a maternally imprinted gene? Reproduction, Fertility and Development 10 (1998) 23–29. [21] T. Hancock, M. Garrett, Beyond medicine: health challenges and strategies in the 21st century, Futures 27 (1995) 935–951. [22] J. Hawks, E.T. Wang, G.M. Cochran, H.C. Harpending, R.K. Moyzis, Recent acceleration of human adaptive evolution, Proceedings of the National Academy of Science of the United States of America 104 (2007) 20753–20758. [23] K. Heath, C. Hadley, Dichotomous Male Reproductive Strategies in a Polygynous Human Society: Mating Versus Parental Effort. Report from The WennerGren, Foundation for Anthropological Research, 1998. [24] E.M. Hill, L.T. Ross, B.S. Low, The role of future unpredictability in human risk-taking, Human Nature 8 (1997) 287–325. [25] D. Kevles, In the Name of Eugenics: Genetics and the Uses of Human Heredity, Knopf, New York, 1985. [26] R.L. Hopcroft, Sex, status, and reproductive success in the contemporary United States, Evolution and Human Behavior 27 (2006) 104–120. [27] J.S. House, Social isolation kills, but how and why? Psychosomatic Medicine 63 (2001) 273–274. [28] K. Kim, P.K. Smith, A.L. Palermiti, Conflict in childhood and reproductive development, Evolution and Human Behavior 18 (1997) 109–142. [29] E. Kolbert, Field Notes from a Catastrophe: Climate Change – Is Time Running Out? Bloomsbury Publishing, London, 2006. [30] D.T. Kenrick, J.A. Simpson, Evolutionary Social Psychology, Lawrence Erlbaum Associates, Mahwah, NJ, 1997. [31] D.J. Kruger, R.M. Nesse, An evolutionary life-history framework for understanding sex differences in human mortality rates, Human Nature 17 (2006) 74–97. [32] D.J. Kruger, R.M. Nesse, Sexual selection, male competition, and sex differences in human mortality rates, in: Presentation at the American College of Epidemiology meeting, Tucson, Arizona, 2008. [33] D.P. Kwiatkowski, How malaria has affected the human genome and what human genetics can teach us about malaria, American Journal of Human Genetics 77 (2005) 171–192.

770

D.J. Kruger / Futures 43 (2011) 762–770

[34] S. Lindeberg, T. Jo¨nsson, Y. Granfeldt, E. Borgstrand, J. Soffman, K. Sjo¨stro¨m, B. Ahre´n, A Palaeolithic diet improves glucose tolerance more than a Mediterranean-like diet in individuals with ischaemic heart disease, Diabetologia 50 (2007) 1795–1807. [35] B. Low, The evolution of human life histories, in: C. Crawford, D. Krebs (Eds.), Handbook of Evolutionary Psychology: Issues, Ideas, and Applications, Lawrence Erlbaum Associates, Mahwah, NJ, 1998, pp. 131–161. [36] R. MacArthur, E.O. Wilson, The Theory of Island Biogeography, Princeton University Press, Princeton, NJ, 1967. [37] F. Marlowe, Hunting and gathering: the human sexual division of foraging labor, Cross-Cultural Research 41 (2007) 170–195. [38] M.G. Marmot, M. Kogevinas, M.A. Elston, Social/economic status and disease, Annual Review of Public Health 8 (1987) 111–135. [39] P. Martens, Health transitions in a globalising world: towards more disease or sustained health? Futures 34 (2002) 635–648. [40] J. McMinn, M. Wei, N. Schupf, J. Cusmai, E.B. Johnson, A.C. Smith, R. Weksberg, H.M. Thaker, B. Tycko, Unbalanced placental expression of imprinted genes in human intrauterine growth restriction, Placenta 27 (2006) 540–549. [41] T. Moore, D. Haig, Genomic imprinting in mammalian development: a parental tug-of-war, Trends in Genetics 7 (1991) 45–49. [42] V. Nell, Why young men drive dangerously: implications for injury prevention, Current Directions in Psychological Science 11 (2002) 75–79. [43] R.M. Nesse, G.C. Williams, Why We Get Sick: The New Science of Darwinian Medicine, Times Books, New York, 1995. [44] M.J. Novacek, Lifetime achievement: E.O. Wilson, CNN interview, 2001. [45] P. Nuttgens, The Story of Architecture, Second ed., Phaidon Press, London, 1997. [46] F. Pearce, The Last Generation: How Nature will take her Revenge for Climate Change, Eden Project Books, London, 2006. [47] E.R. Pianka, On r- and K-selection, American Naturalist 104 (1970) 592–596. [48] J. Poynter, The Human Experiment: Two Years and Twenty Minutes Inside Biosphere 2, Thunder’s Mouth Press, New York, 2006. [49] R.J. Quinlan, Human parental effort and environmental risk, Proceedings of the Royal Society of London Series B 274 (2007) 121–125. [50] A.F. Read, M.J. Mackinnon, Pathogen evolution in a vaccinated world, in: S.C. Stearns, J. Koella (Eds.), Evolution in Health and Disease, Second ed., Oxford University Press, Oxford, 2008, pp. 139–152. [51] W. Reik, M. Constaˆncia, A. Fowden, N. Anderson, W. Dean, A. Ferguson-Smith, B. Tycko, C. Sibley, Regulation of supply and demand for maternal nutrients in mammals by imprinted genes, Journal of Physiology 547 (2003) 35–44. [52] D.A. Roff, The Evolution of Life Histories: Theory and Analysis, Chapman & Hall, New York, 1992. [53] J.P. Rushton, Differential K theory: the sociobiology of individual and group differences, Personality and Individual Differences 6 (1985) 441–452. [54] G. Saad, The Evolutionary Bases of Consumption, Lawrence Erlbaum Associates, Mahwah, NJ, 2007. [55] G. Saad, Suicide triggers as sex-specic threats in domains of evolutionary import: negative correlation between global male-to-female suicide ratios and average per capita gross national income, Medical Hypotheses 68 (2007) 692–696. [56] G. Saad, A. Peng, Applying Darwinian principles in designing effective intervention strategies: the case of sun tanning, Psychology & Marketing 23 (2006) 617–638. [57] U. Segerstra˚le, Defenders of the Truth: The Battle for Science in the Sociobiology Debate and Beyond, Oxford University Press, Oxford, UK, 2000. [58] J. Skripak, R.A. Wood, Exposure to pets, and the association with hay fever, asthma, and atopic sensitization in rural children, Pediatrics 18 (Suppl.) (2006) S7. [59] S.C. Stearns, The Evolution of Life Histories, Oxford University Press, Oxford, 1992. [60] R.W. Summers, D.E. Elliott, J.F. Urban, R. Thompson, J.V. Weinstock, Trichuris suis therapy in Crohn’s disease, Gut 54 (2005) 87–90. [61] E.E. Thompson, H. Kuttab-Boulos, D. Witonsky, L. Yang, B.A. Roe, A. Di Rienzo, CYP3A variation and the evolution of salt-sensitivity variants, The American Journal of Human Genetics 75 (2004) 1059–1069. [62] S.A. Tishkoff, F.A. Reed, A. Ranciaro, B.F. Voight, C.C. Babbitt, J.S. Silverman, K. Powell, H.M. Mortensen, J.B. Hirbo, M. Osman, M. Ibrahim, S.A. Omar, G. Lema, T.B. Nyambo, J. Ghori, S. Bumpstead, J.K. Pritchard, G.A. Wray, P. Deloukas, Convergent adaptation of human lactase persistence in Africa and Europe, Nature Genetics 39 (2007) 7–8. [63] R.L. Trivers, Parent-offspring conflict, American Zoologist 14 (1974) 249–264. [64] D. Waltner-Toews, The end of medicine: the beginning of health, Futures 32 (2000) 655–667. [65] E.O. Wilson, Consilience: The Unity of Knowledge, Knopf, New York, 1998. [66] E.O. Wilson, Biophilia: The Human Bond with Other Species, Harvard University Press, Cambridge, 1984. [67] M. Wilson, M. Daly, Life expectancy, economic inequality, homicide, and reproductive timing in Chicago neighbourhoods, British Medical Journal 314 (1997) 1271–1274.