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Empiricism at all levels
Forum
TRENDS in Ecology & Evolution Vol.17 No.9 September 2002
441
Book Review
Empiricism at all levels Evolutionary Patterns. Growth, Form and Tempo in the Fossil Record edited by Jeremy B.C. Jackson, Scott Lidgard and Frank K. McKinney. The University of Chicago Press, 2001. (xvi + 399 pages) ISBN 0 226 38931 6
Do species evolve directionally along anagenetic pathways? Or are they constrained until the time of speciation? How rapidly does speciation proceed? Is the incremental evolution of a species at all relevant to the pattern of macroevolution of its clade? These questions lie at the heart of studies concerning the tempo and mode of evolution, and Evolutionary Patterns is the latest publication to address these issues. Although the title promises a description of rates and patterns of evolution inferred from the fossil record, the book wisely does not deliver on that promise. Rather, it takes a synthetic approach comprising a diverse array of topics and delivers far more than the usual discussion of punctuated equilibrium versus gradualism, or comparisons of evolutionary rates. The volume is dedicated to Alan Cheetham, and its tribute lies in the diverse, quantitatively oriented, empirically based approaches taken by most of the chapters. The book is arranged somewhat hierarchically, and builds itself from the nuts and bolts of organismal organization and growth, to the analysis and interpretation of large-scale patterns. The first section is a rather eclectic collection of papers with a common neontological basis: Buss discusses growth patterns of hydractinioid colonies; McShea attempts to construct a hierarchical framework for changes in the number of components and modularity at various levels of organismal complexity; and Okamura et al. present a possibly classic study in biological fluid mechanics. On their own, none of these papers addresses tempo and mode over geological http://tree.trends.com
time, but each one provides hypotheses for testing them. Okamura et al.’s contribution is particularly valuable, because it uses morphologies that are well represented in the fossil record, and is a direct test of competition for space as a driving agent of trends in bryozoan evolution. The remaining chapters can be divided into studies dealing with macroevolutionary patterns that are rooted firmly in organismal-level processes and interactions, and those that emerge from such processes or are imposed extrinsically upon the organismal level. For example, Nehm addresses several fundamental questions, such as: are features of morphological evolution similar within and among clades? Do similar developmental processes lead to morphological similarities? And, how does development influence morphological disparity? His study is outstanding, because it combines morphometric description with an independently derived phylogeny. Nehm concludes that, at least for two Neogene gastropods, morphological change during speciation far exceeds variation exhibited by any single lineage during its lifetime. Gould follows with a review of a palaeobiologist’s perception of species concepts, species recognition and speciation processes in the fossil record. The treatments here of morphospecies, stasis and punctuated equilibrium are well developed and broadly inclusive. Gould’s statement, however, that ‘…the punctuation pattern exists at high relative frequencies, and that few gradualistic and anagenetic continua have been documented…’ is based largely on compilations that are of necessity cursory (e.g. [1]), comprising studies that generally fail to appreciate the difficulties inherent in evolutionary pattern recognition. Increased confidence in such compilations depends upon the continued development of methods for analysing fossil and morphological distributions. Hayek and Bura’s chapter is an excellent step in this direction, presenting a new approach for calculating confidence intervals for stratigraphic occurrences. They make the key observation that the derivation of confidence intervals should incorporate sampling beyond the first and last observed occurrences of a taxon, because absences can have multiple causes. This is the most utilitarian chapter, and an interesting
follow-up would be the use of appropriate simulations to test its effectiveness and make comparisons to others (e.g. [2–4]). The hierarchical arrangement of Evolutionary Pattern continues with a consideration of processes that might operate above the species level. Foote takes up the challenge of deconvoluting biological turnover into rates of origination and extinction. This chapter is a wonderful abstraction of organismallevel happenings and requires little biological information for exploration of the underlying model. However, readers should be aware of the abstraction before interpreting the model. For example, rates of change in diversity do not necessarily represent rates of evolution. This is done only by the origination rate, and then only at the species level, because higher taxa do not evolve. Foote’s observation of the symmetry and time reversibility of his equations is a point worth noting. Translating this empirically, one can ask whether the processes that cause extinction within a taxon are likely to be the same ones that promote origination. Perhaps this challenge is taken up by most of the remaining chapters. Pandolfi et al. and Budd and Johnson examine diversity changes in late Cenozoic corals, focusing on rapid extinction and biotic turnover respectively. These are both excellent chapters and lead to questions that bridge evolutionary biology and palaeoecology; do ecological relationships at lower taxonomic levels scale up taxonomically and temporally? Do ultimate causes of extinction [5] operate most effectively at the level of geographical range, whilst proximal causes interact most strongly with rarity? When and why are rare species never widespread geographically (geographically widespread does not imply numerically abundant)? The last chapters take the final hierarchical steps. Håkansson and Thomsen examine the macroevolutionary trend toward asexual reproduction in cheilostome bryozoans. McKinney et al. take an almost meta-analytic approach to the relationship between macroevolution and macroecology, emphasizing the importance of abundance data, and the danger of reliance on species lists in studies at these highest of Phanerozoic palaeobiological levels. The book closes with a well-founded caution that, as we
0169-5347/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved.
442
Forum
TRENDS in Ecology & Evolution Vol.17 No.9 September 2002
move from the descriptive to analytical phases in palaeontology, the necessity, nature and quality of our empirical data are of paramount importance. Evolutionary Patterns is a refreshing, timely addition to the evolutionary biology literature, heralding the rapid transition of our endeavors from largely descriptive and hypothesis-generating activities, to empiricism at all levels of the evolutionary hierarchy. Many readers will find it a satisfying compilation. For others, such as myself, it is ultimately unsatisfying, raising far more questions than providing answers – precisely why it is an essential item for any palaeobiologist or evolutionary biologist. Peter D. Roopnarine Dept of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, CA 94118-4599 USA. e-mail: [email protected] References 1 Erwin, D.H. and Anstey, R.L., eds (1995) New Approaches to Speciation in the Fossil Record, Columbia University Press 2 Marshall, C.R. (1990) Confidence intervals on stratigraphic ranges. Paleobiology 16, 1–10 3 Marshall, C.R. (1994) Confidence intervals on stratigraphic ranges: partial relaxation of the assumption of randomly distributed fossil horizons. Paleobiology 20, 459–469 4 Strauss, D. and Sadler, P.M. (1987) Confidence Intervals for the Ends of Local Taxon Ranges, Technical Report 158, Dept of Statistics, University of California, Riverside 5 Simberloff, D. (1986) The proximate causes of extinction. Life Sci. Res. Report 36, 259–276
Published online: 7 June 2002
Does commitment make evolutionary sense? Evolution and the Capacity for Commitment edited by Randolph M. Nesse. Russell Sage Foundation, 2001. US$42.50, hbk. (xviii + 334 pages). ISBN 0 87154 622 1
This edited volume is a multidisciplinary examination of the concept of commitment, emphasizing evolutionary aspects. As defined by the editor, http://tree.trends.com
commitment refers to ‘an act or signal that gives up options in order to influence someone’s behavior by changing incentives or expectations’. The concept, first articulated in a game-theoretical framework by political economist Schelling [1], has since been employed to analyse everything from nuclear deterrence to friendship and love. The evolution of commitment was first given an extended treatment in the late 1980s, in independent treatments by two economists with evolutionary interests (Hirshleifer and Frank). It is a measure of the authority of the work under review that all three of these scholars contribute chapters, as do anthropologists, psychologists, behavioral ecologists, a philosopher and a legal scholar. In a useful introductory chapter, Nesse (a psychologist known for writings on evolutionary medicine) outlines four types of commitment: (1) self-enforcing via intrinsic constraints (e.g. burning your bridges behind you); (2) enforced by incentives controlled by others (e.g. making a down payment on a purchase); (3) enforced by a concern for reputation (e.g. responding to an insult with a challenge to duel); and (4) enforced by subjective emotional states (e.g. remaining with a partner in spite of their long, terminal illness). The first two are ‘secured’ commitments, whereas the latter two are ‘unsecured’ (or what Nesse terms ‘subjective commitments’) and constitute the prime focus of the book. As this classification suggests, a key issue for understanding the evolution and stability of commitments is what makes them credible. The paradox of commitment is that it forecloses options that would otherwise be in the actor’s best interests – cheating, desertion or retreat. Secured commitments alter the external incentives in some way (e.g. by making retreat difficult or impossible, burning bridges increases the incentive for fighting hard, which could serve to deter the enemy); but once the commitment is made, the rational or adaptive response is readily predicted. Because unsecured (subjective) commitments present a continuing option for defection, they pose a greater challenge to standard rational-choice and adaptationist accounts of behavior – a challenge viewed in various distinct ways by the volume’s contributors. Of the three contributions by economists, only Hirshleifer’s offers any
formal theory (which is scarce in the volume as a whole). He utilizes game theory to explore the effects on commitment of both changes in payoff structure (e.g. prisoner’s dilemma versus chicken) and protocols of play (e.g. pre-emptive first-move commitment versus reactive second-move commitment). Similar to several other contributors, Hirshleifer notes the important role that emotions can play in motivating commitment; for example, ‘hot anger serves to deter undesired behavior by making the threat of punishing response credible, even if executing that punishment is not materially profitable’. Of the chapters by behavioral ecologists, I found that by Adams to be the most rewarding. In his summary and discussion of animal threat displays, Adams finds much evidence – and a sound evolutionary basis in signaling theory – for secured commitments and those involving reputation (i.e. the first three types in Nesse’s typology), but none for type 4 (emotional commitment). Although recognizing the difficulty of demonstrating such emotionally enforced commitment in nonhuman organisms, Adams is skeptical on theoretical grounds: ‘An animal that appears to be committed, but in fact can back out when it is favorable to do so, often will fare better than one that is truly committed’. If there is no reason to rule out the evolution of deception, emotional commitment will not be evolutionarily stable. Dugatkin briefly relates commitment to the evolutionary analysis of cooperation, and suggests ways to design experiments that might reveal subjective commitment in nonhumans. Silk summarizes evidence from primates concerning signals of intent. Remaining chapters are diverse but uniformly accessible and interesting. Cohen and Vandello summarize research on the ‘culture of honor’ (particularly among southern white Americans), noting that these tend to arise in places where external enforcement (e.g. government) is weak or absent and wealth is portable (hence stealable). Richerson and Boyd discuss the costly commitments that humans often make to large groups (clan, tribe or nation), and argue that these are best explained via processes of cultural group selection. Irons briefly surveys ‘religion as a hard-to-fake sign of commitment’, whilst Goodenough discusses legal codes and practices as
0169-5347/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved.
TRENDS in Ecology & Evolution Vol.17 No.9 September 2002
441
Book Review
Empiricism at all levels Evolutionary Patterns. Growth, Form and Tempo in the Fossil Record edited by Jeremy B.C. Jackson, Scott Lidgard and Frank K. McKinney. The University of Chicago Press, 2001. (xvi + 399 pages) ISBN 0 226 38931 6
Do species evolve directionally along anagenetic pathways? Or are they constrained until the time of speciation? How rapidly does speciation proceed? Is the incremental evolution of a species at all relevant to the pattern of macroevolution of its clade? These questions lie at the heart of studies concerning the tempo and mode of evolution, and Evolutionary Patterns is the latest publication to address these issues. Although the title promises a description of rates and patterns of evolution inferred from the fossil record, the book wisely does not deliver on that promise. Rather, it takes a synthetic approach comprising a diverse array of topics and delivers far more than the usual discussion of punctuated equilibrium versus gradualism, or comparisons of evolutionary rates. The volume is dedicated to Alan Cheetham, and its tribute lies in the diverse, quantitatively oriented, empirically based approaches taken by most of the chapters. The book is arranged somewhat hierarchically, and builds itself from the nuts and bolts of organismal organization and growth, to the analysis and interpretation of large-scale patterns. The first section is a rather eclectic collection of papers with a common neontological basis: Buss discusses growth patterns of hydractinioid colonies; McShea attempts to construct a hierarchical framework for changes in the number of components and modularity at various levels of organismal complexity; and Okamura et al. present a possibly classic study in biological fluid mechanics. On their own, none of these papers addresses tempo and mode over geological http://tree.trends.com
time, but each one provides hypotheses for testing them. Okamura et al.’s contribution is particularly valuable, because it uses morphologies that are well represented in the fossil record, and is a direct test of competition for space as a driving agent of trends in bryozoan evolution. The remaining chapters can be divided into studies dealing with macroevolutionary patterns that are rooted firmly in organismal-level processes and interactions, and those that emerge from such processes or are imposed extrinsically upon the organismal level. For example, Nehm addresses several fundamental questions, such as: are features of morphological evolution similar within and among clades? Do similar developmental processes lead to morphological similarities? And, how does development influence morphological disparity? His study is outstanding, because it combines morphometric description with an independently derived phylogeny. Nehm concludes that, at least for two Neogene gastropods, morphological change during speciation far exceeds variation exhibited by any single lineage during its lifetime. Gould follows with a review of a palaeobiologist’s perception of species concepts, species recognition and speciation processes in the fossil record. The treatments here of morphospecies, stasis and punctuated equilibrium are well developed and broadly inclusive. Gould’s statement, however, that ‘…the punctuation pattern exists at high relative frequencies, and that few gradualistic and anagenetic continua have been documented…’ is based largely on compilations that are of necessity cursory (e.g. [1]), comprising studies that generally fail to appreciate the difficulties inherent in evolutionary pattern recognition. Increased confidence in such compilations depends upon the continued development of methods for analysing fossil and morphological distributions. Hayek and Bura’s chapter is an excellent step in this direction, presenting a new approach for calculating confidence intervals for stratigraphic occurrences. They make the key observation that the derivation of confidence intervals should incorporate sampling beyond the first and last observed occurrences of a taxon, because absences can have multiple causes. This is the most utilitarian chapter, and an interesting
follow-up would be the use of appropriate simulations to test its effectiveness and make comparisons to others (e.g. [2–4]). The hierarchical arrangement of Evolutionary Pattern continues with a consideration of processes that might operate above the species level. Foote takes up the challenge of deconvoluting biological turnover into rates of origination and extinction. This chapter is a wonderful abstraction of organismallevel happenings and requires little biological information for exploration of the underlying model. However, readers should be aware of the abstraction before interpreting the model. For example, rates of change in diversity do not necessarily represent rates of evolution. This is done only by the origination rate, and then only at the species level, because higher taxa do not evolve. Foote’s observation of the symmetry and time reversibility of his equations is a point worth noting. Translating this empirically, one can ask whether the processes that cause extinction within a taxon are likely to be the same ones that promote origination. Perhaps this challenge is taken up by most of the remaining chapters. Pandolfi et al. and Budd and Johnson examine diversity changes in late Cenozoic corals, focusing on rapid extinction and biotic turnover respectively. These are both excellent chapters and lead to questions that bridge evolutionary biology and palaeoecology; do ecological relationships at lower taxonomic levels scale up taxonomically and temporally? Do ultimate causes of extinction [5] operate most effectively at the level of geographical range, whilst proximal causes interact most strongly with rarity? When and why are rare species never widespread geographically (geographically widespread does not imply numerically abundant)? The last chapters take the final hierarchical steps. Håkansson and Thomsen examine the macroevolutionary trend toward asexual reproduction in cheilostome bryozoans. McKinney et al. take an almost meta-analytic approach to the relationship between macroevolution and macroecology, emphasizing the importance of abundance data, and the danger of reliance on species lists in studies at these highest of Phanerozoic palaeobiological levels. The book closes with a well-founded caution that, as we
0169-5347/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved.
442
Forum
TRENDS in Ecology & Evolution Vol.17 No.9 September 2002
move from the descriptive to analytical phases in palaeontology, the necessity, nature and quality of our empirical data are of paramount importance. Evolutionary Patterns is a refreshing, timely addition to the evolutionary biology literature, heralding the rapid transition of our endeavors from largely descriptive and hypothesis-generating activities, to empiricism at all levels of the evolutionary hierarchy. Many readers will find it a satisfying compilation. For others, such as myself, it is ultimately unsatisfying, raising far more questions than providing answers – precisely why it is an essential item for any palaeobiologist or evolutionary biologist. Peter D. Roopnarine Dept of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, CA 94118-4599 USA. e-mail: [email protected] References 1 Erwin, D.H. and Anstey, R.L., eds (1995) New Approaches to Speciation in the Fossil Record, Columbia University Press 2 Marshall, C.R. (1990) Confidence intervals on stratigraphic ranges. Paleobiology 16, 1–10 3 Marshall, C.R. (1994) Confidence intervals on stratigraphic ranges: partial relaxation of the assumption of randomly distributed fossil horizons. Paleobiology 20, 459–469 4 Strauss, D. and Sadler, P.M. (1987) Confidence Intervals for the Ends of Local Taxon Ranges, Technical Report 158, Dept of Statistics, University of California, Riverside 5 Simberloff, D. (1986) The proximate causes of extinction. Life Sci. Res. Report 36, 259–276
Published online: 7 June 2002
Does commitment make evolutionary sense? Evolution and the Capacity for Commitment edited by Randolph M. Nesse. Russell Sage Foundation, 2001. US$42.50, hbk. (xviii + 334 pages). ISBN 0 87154 622 1
This edited volume is a multidisciplinary examination of the concept of commitment, emphasizing evolutionary aspects. As defined by the editor, http://tree.trends.com
commitment refers to ‘an act or signal that gives up options in order to influence someone’s behavior by changing incentives or expectations’. The concept, first articulated in a game-theoretical framework by political economist Schelling [1], has since been employed to analyse everything from nuclear deterrence to friendship and love. The evolution of commitment was first given an extended treatment in the late 1980s, in independent treatments by two economists with evolutionary interests (Hirshleifer and Frank). It is a measure of the authority of the work under review that all three of these scholars contribute chapters, as do anthropologists, psychologists, behavioral ecologists, a philosopher and a legal scholar. In a useful introductory chapter, Nesse (a psychologist known for writings on evolutionary medicine) outlines four types of commitment: (1) self-enforcing via intrinsic constraints (e.g. burning your bridges behind you); (2) enforced by incentives controlled by others (e.g. making a down payment on a purchase); (3) enforced by a concern for reputation (e.g. responding to an insult with a challenge to duel); and (4) enforced by subjective emotional states (e.g. remaining with a partner in spite of their long, terminal illness). The first two are ‘secured’ commitments, whereas the latter two are ‘unsecured’ (or what Nesse terms ‘subjective commitments’) and constitute the prime focus of the book. As this classification suggests, a key issue for understanding the evolution and stability of commitments is what makes them credible. The paradox of commitment is that it forecloses options that would otherwise be in the actor’s best interests – cheating, desertion or retreat. Secured commitments alter the external incentives in some way (e.g. by making retreat difficult or impossible, burning bridges increases the incentive for fighting hard, which could serve to deter the enemy); but once the commitment is made, the rational or adaptive response is readily predicted. Because unsecured (subjective) commitments present a continuing option for defection, they pose a greater challenge to standard rational-choice and adaptationist accounts of behavior – a challenge viewed in various distinct ways by the volume’s contributors. Of the three contributions by economists, only Hirshleifer’s offers any
formal theory (which is scarce in the volume as a whole). He utilizes game theory to explore the effects on commitment of both changes in payoff structure (e.g. prisoner’s dilemma versus chicken) and protocols of play (e.g. pre-emptive first-move commitment versus reactive second-move commitment). Similar to several other contributors, Hirshleifer notes the important role that emotions can play in motivating commitment; for example, ‘hot anger serves to deter undesired behavior by making the threat of punishing response credible, even if executing that punishment is not materially profitable’. Of the chapters by behavioral ecologists, I found that by Adams to be the most rewarding. In his summary and discussion of animal threat displays, Adams finds much evidence – and a sound evolutionary basis in signaling theory – for secured commitments and those involving reputation (i.e. the first three types in Nesse’s typology), but none for type 4 (emotional commitment). Although recognizing the difficulty of demonstrating such emotionally enforced commitment in nonhuman organisms, Adams is skeptical on theoretical grounds: ‘An animal that appears to be committed, but in fact can back out when it is favorable to do so, often will fare better than one that is truly committed’. If there is no reason to rule out the evolution of deception, emotional commitment will not be evolutionarily stable. Dugatkin briefly relates commitment to the evolutionary analysis of cooperation, and suggests ways to design experiments that might reveal subjective commitment in nonhumans. Silk summarizes evidence from primates concerning signals of intent. Remaining chapters are diverse but uniformly accessible and interesting. Cohen and Vandello summarize research on the ‘culture of honor’ (particularly among southern white Americans), noting that these tend to arise in places where external enforcement (e.g. government) is weak or absent and wealth is portable (hence stealable). Richerson and Boyd discuss the costly commitments that humans often make to large groups (clan, tribe or nation), and argue that these are best explained via processes of cultural group selection. Irons briefly surveys ‘religion as a hard-to-fake sign of commitment’, whilst Goodenough discusses legal codes and practices as
0169-5347/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved.