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Evolutionary Psychology and the Social Sciences By Todd J. Zywicki

Recent years have seen an explosion in interest in evolutionary biology and its implications for the social sciences. Few areas of social science research have been untouched by the Darwinian revolution currently taking place. Economics, sociology, political science, law, history, psychology, philosophy, and anthropology have seen Darwinian arguments slowly gravitate from the periphery toward the center of their disciplines. The purpose of this essay is to provide an introduction to the field and to suggest future avenues for further research in the intersection between evolutionary biology and the humane sciences.

It is a fortuitous time for young scholars interested in the application of Darwinian evolution to problems of social science. Increasing understanding of DNA sequencing, combined with the impetus of the human genome project, have given rise to an unprecedented understanding of the genetic basis of much of our physical and mental natures. These developments have also eroded some of the stigma associated with prior efforts to apply Darwinian evolution to the study of human society, the most recent being E. O. Wilson’s Sociobiology, which met with a firestorm of protest when published in the 1975. See E. O. Wilson, Sociobiology: The New Synthesis (1975) (Cambridge, Mass.: Harvard University Press). Today the field travels under a variety of names; although the traditional term “sociobiology” is still occasionally used, more common today is evolutionary psychology, which is can be classified as a subset of evolutionary biology of “neo-Darwinism.”

The negative political reception of Wilson’s Sociobiology set back the field for an entire generation of social scientists. This means that there remains a large degree of low-hanging fruit for young scholars to pluck in forming a research agenda in the field. Moreover, because much of the science remains fluid and ongoing, working in the field requires a degree of mental dexterity and the development of new skills that provides a comparative advantage to younger scholars.

This essay will not attempt to provide a comprehensive guide to the field of evolutionary psychology. The field is vast and can become technical very quickly. This essay therefore will only attempt to provide an overview and introduction to the field. The sources mentioned will generally be highly comprehensive and generally provide detailed references for those interested in pursuing issues in greater depth. Indeed, this work will not attempt to identify more than a handful of the interesting social science issues that seem to be worth exploring through the lens of evolutionary psychology. Indeed, this portion of the essay is avowedly idiosyncratic and subjective, and is intended primarily to suggest some of the types of questions that can be gainfully addressed through a Darwinian framework.

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In the remainder of the essay I will first discuss why an understanding of evolutionary psychology is useful for those interested in studying the social sciences. The next section will provide an overview of some of the important concepts that have emerged from evolutionary psychology, focusing in particular on the “four paths to cooperation” that have been identified by scholars. The final section will discuss some of the implications of evolutionary psychology for research in different fields of inquiry.

Why Study Evolutionary Psychology?

Most classical liberals are somewhat skeptical about the value of studying evolutionary psychology. To some extent this is rooted in the historical association of classical liberalism with the mistaken tenets of “Social Darwinism” at the turn of the century. To some extent this skepticism resides in the frosty reception of sociobiology by a prior generation of scholars. Finally, to some extent this skepticism resides in a misunderstanding of the import of evolutionary psychology, and in particular in the belief that evolutionary psychology believes in the perfect determinacy of human behavior. This latter belief makes evolutionary psychology anathema to those concerned about issues of free will and personal autonomy.

This skepticism is unfounded. Social Darwinism was a perversion of the insights of evolutionary psychology. Social Darwinists committed the classic naturalist fallacy, reasoning from the empirical observation that evolution operated according to the principle of the “survival of the fittest” to the normative conclusion that it should be the job of society to weed out the weak so as to further this evolutionary imperative. In so doing, Social Darwinists jumped from the “is” of evolution to the “ought” that the product of natural evolution is morally justified. Interestingly, today some environmentalists are prone to commit the naturalist fallacy in their belief that somehow what is “natural” is morally preferable to that which is not. On the other hand, this does not rule out a belief that what is normatively good for human beings must in some sense be consistent with their fundamental psychological natures. See E. O. Wilson, Consilience: The Unity of Knowledge (New York: Alfred A. Knopf, 1998); R. D. Alexander, The Biology of Moral Systems (Hawthorne, N.Y.: Aldine De Gruyter, 1987). This latter argument recognizes the “is-ought” gap, so the naturalistic fallacy is avoided. Nonetheless, it argues that individuals will flourish only if they act consistently with their evolved natures. See Owen D. Jones, “On the Nature of Norms: Biology, Morality, and the Disruption of Order,” Michigan Law Review 98: 801-832 (Forthcoming 2000).

Whether a particular behavior is normatively good or bad cannot be established simply by determining that the actor is “naturally” inclined to behave in such a manner. Certain behaviors can be good or bad only according to an external normative standard. Thus, as discussed below it appears that human beings may be naturally predisposed to engage in trade, act compassionately, and enter into reciprocal arrangements for mutual benefit. By almost any moral code, all of these behaviors are normatively good. By contrast, it also appears that some human beings may be predisposed naturally toward violence and rape. See Randy Thornhill and Craig T. Palmer, A Natural History of Rape: Biological Bases of Sexual Coercion (Cambridge: MIT Press, 2000); Owen D. Jones,

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“Sex, Culture, and the Biology of Rape: Toward Explanation and Prevention,” California Law Review 827-941 (1999). The fact that these behaviors are “natural” is irrelevant to the fact that they are universally morally condemned. Finally, other predispositions, such as our tendencies to eat too many candy bars, are morally neutral. The desire to consume sugar served an evolutionary purpose in an era where food was scarce and it was useful to have a built-in craving to encourage us to seek food. The task of the philosopher and social scientist is to understand the degree to which certain predilections are hard-wired into human psychology, and thereby to determine what set of institutions and incentives are necessary to restrain, modify, or channel these predilections into pro-social behavior and away from anti-social behavior.

Moreover, evolutionary psychology does not imply biological determinism. Modern biology makes clear, rather, that one’s behavior is a function of the mutual interaction between evolved traits and one’s environment, or as the case is frequently (if inaccurately) put, between nature and nurture. Indeed, evolution itself is driven by the interaction of biological variation interacting with environmental selection. There are no absolute degrees of fitness, only comparative degrees of fitness relative to a given environment. Evolutionary psychology simply provides evidence of general tendencies that interact with an individual’s environment. At the same time, evolutionary psychology rejects the claims of current theorists who argue that one’s personality is entirely socially constructed and thus infinitely malleable. As Marxists learned the hard way, there are certain characteristics of human nature that seem to be virtually impossible to eliminate, such as the tendency to prefer the welfare of one’s family to strangers, the tendency to free ride on others’ labors where possible, and the tendency to seek wealth and status. Thus, although the morality of a given behavior cannot be determined simply by whether it is natural, the recognition that there are certain hard-wired tendencies to human nature may constrain what aspirations are attainable or may provide guidance as to what tools are available to accomplish one’s goals. Thus, evolutionary psychology illustrates the folly of the scholarship of recent decades that has tried to ignore the reality of an innate human nature that is not infinitely malleable. More fundamentally, it provides a warning against indulging in the utopian schemes characteristic of the twentieth century, most of which rested on the supposition that human nature could be molded to fit the desires of utopian reformers, rather than recognizing the limits that human nature placed on such schemes.

It is now generally accepted that evolutionary biology provides a persuasive explanation for our biological natures, e.g., two arms, two legs, upright gait, vision, hearing, warm-bloodedness, etc. Although evolutionary biology has triumphed for biological evolution, scholars remain reluctant to recognize that evolution has psychological consequences as well. Instead, scholars have preferred to believe that humans remain a tabula rasa, blank personalities subject to molding by social, cultural, legal, political, and economic forces. I have elsewhere dubbed this incongruity, “Darwinism from the neck up,” because even as secular scholars have generally embraced biological Darwinism, they have rejected psychological Darwinism with equally forceful zeal. See Todd J. Zywicki, “The State of Nature and the Nature of the State: A Comment on Grady and McGuire,” Journal of Bioeconomics 1(3): 241-261 (1999). The flaw in this

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reasoning is obvious. Just as we have physically evolved to solve a number of common problems that arose in our evolutionary environment, we have similarly developed psychological skills necessary to operate in the social environment of our evolutionary ancestors. Put more simply, nobody believes that education or culture will make me physically able to dunk a basketball; why are Marxists so optimistic that education, economic, and political reform could make me treat strangers as if they were my genetic kin?

For most animals the relevant variable for one’s evolutionary fitness turns on the fitness for a given physical environment. Thus, a wolf’s fitness will be a function of its ability to hunt down elk and an elk’s fitness will be a function of its ability to outrun and evade wolves. For humans, however, the relevant environment primarily is other humans, a social environment rather than a physical environment. Because of the immensely social nature of human societies, one’s fitness is not merely a function of the ability to seek prey and to avoid predation. Rather, human societies place a fundamental premium on the ability to interact with other human beings in a social environment. The evolutionary environment for humans is the body of institutions, rules, customs, and expectations of others. Thus, the fundamental evolutionary difficulty for humans is to solve inherently social puzzles as to how to interact with others. Although other animals have some degree of culture, none of them even approximates the complexity of even the simplest human cultures. See F. De Waal, “Cultural Primatology Comes of Age,” Nature 399:635-636 (1999). A massive database has been established to collate the various different chimpanzee cultures that researchers have identified. See A. Whiten, et al. “Cultures in Chimpanzees,” Nature 399:682-685 (1999). Their results can be found on-line at <http://www.chimp-st-and.ac.uk/cultures/database.htm>.

An incongruity arises in that evolutionary psychologists recognize that the social problems that humans must solve are not actually the social problems of today’s global economy, but that our minds are molded to solve the social problems of our human ancestors. Our brains and minds (as with our bodies) took on their current configuration in what is generally referred to as the Environment of Evolutionary Adaptedness, or EEA, during the Pleistocene Era several million years ago. During this time our human ancestors lived in small, stable hunter-gatherer bands characterized by stable social groups, repeated interaction over time, and relatively long life spans. In evolutionary terms a few million years is a relatively short amount of time. Thus it is believed that humans have largely the same biological natures as the humans of hunter-gatherer time. Cultural evolution, however, operates much more rapidly than biological evolution. Thus, we live in high-speed global economies characterized by rapid economic change, although our essential natures remain essentially hunter-gatherer in nature. This creates a mismatch between some of our innate desires and the realities we confront on a daily basis. See F. A. Hayek, The Fatal Conceit: The Errors of Socialism (1988) (The Collected Works of F. A. Hayek, W. W. Bartley III ed., Chicago: University of Chicago Press). For Hayek, therefore, the purpose of culture and institutions is to control our self-destructive impulses to impose our small-group sentiments on modern society. Robert Wright, by contrast, builds on the foundation of human sociability and argues that biological and cultural evolution share the common trait that they both have a tendency

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toward increasing complexity driven by the mutual benefits of “non-zero-sum exchange.” See Robert Wright, Nonzero: The Logic of Human Destiny (2000) (New York: Pantheon Books). Unlike Hayek, therefore, Wright views culture and institutions as the extension of an innate tendency to engage in mutually beneficial exchange, without Hayek’s emphasis on the small-group setting of the EEA.

Just as the study of evolutionary biology should not be interpreted to denigrate the importance of environmental factors, it should also not be interpreted to denigrate the value of free will and purposefulness in human action. It is true that some commentators such as Robert Wright have suggested that evolutionary psychology calls into question the entire concept of free will by reducing human action to a predictable set of impulses. See Robert Wright, The Moral Animal: Evolutionary Psychology and Everyday Life (1994) (New York: Vintage Books). Others, however, have argued that a proper understanding of science and human nature actually enhances the importance of free will and moral decision by recognizing the importance of restraining our anti-social and unhealthy impulses even when tempted to act otherwise. See Pope John Paul II, “Message to Pontifical Academy of Sciences,” The Vatican (Oct. 22, 1996). Studying animal behavior and cooperation, therefore, is useful in the same way that game theory is useful, to provide evidence of how humans might be predicted to act absent the restraints of human nature and social institutions and norms. Studying animal behavior provides insight on possible solutions to various problems of human societies, such as problems of collective action, conflict resolution, and the like. Social animals are confronted with many of the same problems as human societies, of keeping internal peace and resolving conflicts over scarce resources. And they do so without any sophisticated cultural or institutional mechanisms. As evolutionary biologist Lee Dugatkin observes, Lee Dugatkin, Cheating Monkeys and Citizen Bees: The Nature of Cooperation in Animals and Humans (New York: Free Press, 1999), studying human behavior and cooperation:

shows us what to expect when the complex web of human social networks, as well as the laws and norms found in all human societies, are absent, and so these studies act as a sort of baseline from which to operate. Animals show us a stripped-down version of what behavior in a given circumstance would look like without moral will and freedom. Only with this understanding of what a particular behavior looks like outside the context of some moral code can we use human morality to focus on and foster cooperation in our species.1

Four Paths to Cooperation

Thomas Hobbes famously claimed that absent a central political authority the state of nature would devolve into a war of “all against all.” Selfish individuals, he believed, would be unable to cooperate for mutual advantage because of the constant temptation for individuals to take advantage of one another. Stated in modern game theory terms,

1 Dugatkin, Cheating Monkeys, pp. 14-15.

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Hobbes believed that individuals would “defect” in every interaction they had with one another. The insights of evolution rebut Hobbes’s belief. All living creatures face certain difficulties maintaining social cooperation and peace. This section will review the “four paths to cooperation” that evolutionary biologists have identified as mechanisms for creating social peace without the necessity of a central rule-making authority. In fact, most cooperation in nature exists not only without legal and political institutions, but also without what has fashionably come to be called “norms” and which previously was called custom. Norms and institutions can extended the sphere of cooperation, but it appears that much cooperative behavior is in fact natural and rooted in human nature. It is likely that the presence of a hard-wired tendency toward cooperation is a necessary condition for the emergence of social cooperation; indeed, in many animal societies it is also a sufficient condition.

Although Hobbes’s solution was utterly confused, he posed the correct question – how can selfish individuals be induced to cooperate with one another? Biologists start with a similar reductionist premise. Rather than selfish individuals, however, biologists begin their analysis with selfish genes. See Richard Dawkins, The Selfish Gene (2d edition, 1989) (New York: Oxford University Press). The two are closely related but analytically distinct. Genes are the basic units of natural selection; individuals can be understood as collections of genes. The only measure of success for a gene is its ability to be replicated into a new generation. Genes produce phenotypic traits in human beings, such as intelligence, athleticism, and physical appearance, that when selected for by the environment, affect an individual’s likelihood of successfully mating and passing along his or her genetic material to a new generation. Matt Ridley provides an excellent introduction to the ways in which genotypes are reflected in specific human phenotypic traits. See Matt Ridley, Genome: The Autobiography of a Species in 23 Chapters (London: Fourth Estate, 1999). In this sense genes can be figuratively said to be “selfish” in the same way an individual can be said to be selfish (even though genes do not act with “intent”); particular genes “care” only about their own survival into a new generation. Thus, genes are “selfish,” and do not “care” about the plight of any other genes, except to the extent that it helps that particular gene survive into the next generation. In turn, this suggests that individuals will act in the self-interest of his genes.

This analysis really just restates the basic question: given the existence of selfish genes, why do we see so many instances of cooperation among animals, including human beings? Lee Dugatkin provides a virtual encyclopedia of documentation and explanation of cooperation among animals in Cooperation Among Animals: An Evolutionary Perspective (New York: Oxford University Press, 1997). Moreover, cooperation in non-human animals is especially puzzling, given the absence of cultural norms or a state to enforce compliance with cooperative behavior.

Four mechanisms have been suggested by evolutionary biologists to explain the evolution of cooperation in nature: (1) kin selection, (2) cooperation for mutual advantage, (3) reciprocal altruism, and (4) group selection. In each of these situations, one individual (i.e., collection of genes) acts altruistically in bestowing a benefit upon some other individual (collection of genes). This is surprising, in that it seems to be

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inconsistent with the self-interest axiom. Nonetheless, each of these mechanisms potentially makes it more likely that certain genes will be propagated in a new generation. Sometimes the benefit for the genes is direct, as in the kin selection model. For others it is indirect, in that by pursuing cooperation an individual increases his wealth and health, increasing his reproductive capacity relative to less cooperative individuals. This section of the essay will discuss each of these paths to cooperation in turn.

Kin Selection

Kin selection operates on the premise that the marginal sacrifice of one individual may make that individual relatively worse off, but that the sacrifice may also make that individual’s genes better off as a result. For instance, consider the following situation confronting a family of ground squirrels. Amy the ground squirrel is out foraging for food one day with her sisters when she spots a hawk circling above. At this point, Amy has two options: she can either quietly slink back to the lair, leaving the hawk to eat a less-observant sister. Alternatively, she can sound a warning call, thereby alerting Betty, Claire, Denise, Edith, and Francis that a hawk has been spotted and warning them to retreat to the lair. Assume further that if she sounds the call, it will increase her likelihood of being eaten by the hawk by 10% but will reduce the likelihood of her sisters being eaten by 5% each. Will she call the alarm?

Surprisingly, the answer is yes for Belding’s ground squirrels. See Paul W. Sherman, “Nepotism and the Evolution of Alarm Calls,” Science 197: 1246-1253 (Sept. 23, 1977). For a less technical presentation, see Lee Dugatkin, Cheating Monkeys and Citizen Bees: The Nature of Cooperation in Animals and Humans (New York: Free Press, 1999). Although it makes it more likely that Amy will be killed, it makes it sufficiently less likely that her sisters will be eaten that it is worth it for her to call the alarm. Even though sounding an alarm call is dangerous to the individual caller’s survival, it is favorable toward the caller’s genes. Individual ground squirrels (as with most animals) are diploid, meaning that they draw one-half of their chromosomes from each of their two parents (a female mother and a male father). This means that on average Amy shares 50% of her genes with her sisters. Thus, even though Amy’s call decreases her likelihood of surviving the hawk attack by 10%, it increases the overall likelihood of saving her sisters by 25% (five sisters times 5% increased likelihood of survival). Because Amy shares on average 50% of her genes with her sisters, sounding the alarm call will increase the likelihood of her genes surviving by 12-1/2% overall (25% times 50%), while costing her only a 10% likelihood of being eaten. Thus, while it is irrational from Amy’s individual perspective to call the alarm, it is “rational” from her genes’ perspective to induce Amy to call the alarm.

This tendency to act altruistically toward one’s kin is called “inclusive fitness.” See W. D. Hamilton, “The Genetical Evolutionary of Social Behavior, Parts I and II,” Journal of Theoretical Biology 7:1-52 (1964); J. Maynard Smith, “Group Selection and Kin Selection,” Nature 201:1145-1147 (1964). The theory of inclusive fitness predicts that natural selection will favor altruism among kin: the closer two individuals are related to one another, the lower the costs to the altruist, and the greater the benefits to the

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recipient. Therefore, if the five individuals that Amy’s call would save were grandchildren, rather than her sisters, each individual granddaughter would have only a 25% expected relatedness to Amy. As a result, it would be “irrational” for Amy to sound the alarm, as she would be increasing her likelihood of being attacked by 10%, but only increasing the likelihood of her genes’ survival by 6.25%. Restated, natural selection predicts that, on average, we would tend to act more altruistically toward siblings, parents, and children with whom we share an average relatedness of 50% than toward grandparents, grandchildren, aunts, and uncles, with whom we share an average relatedness of only 25%. Interestingly, this theory also provides no instinctive reason why we would act more altruistically toward a spouse than toward a stranger. Thus, the observed tendency to act altruistically towards one’s spouse must rest on some other basis than the theory of inclusive fitness.

This is not to imply that ground squirrels make such rational calculations in deciding whether to issue an alarm in a given situation (“Let me see, how many sisters and granddaughters are around right now ...”). There is a burgeoning literature on how animals determine who is kin and who is not. See P. G. Hepper, Kin Recognition (Cambridge: Cambridge University Press, 1991). Most of the methods of identification, such as close inspection of physical features or odors, are relatively costly to perform. Thus, rather than engaging in a close inspection of every member of an animal society, most animals seem to rely on the simple heuristic of treating as kin everyone who grew up in the relevant area (e.g., nest, territory, burrow, etc.). As a rule of thumb, this approach is subject to error, most notably by animal parasites who try to trick other animals into raising their offspring (suck as cuckoos). But in general, treating those with whom you grew up as kin provides a pretty accurate shortcut for determining who is kin and who is not. Thus, it is interesting to note that the so-called “incest taboo” of not being attracted to kin actually appears to be not so much an aversion on being attracted to a relative, but instead is an aversion against being attracted to a person with whom you grew up. See E. A. Westermarck, The History of Human Marriage (New York: Macmillan, 1891). Thus, stepsiblings raised together are rarely attracted to one another, as are very close childhood friends. By contrast, this further suggests that if sexual activity takes place within the family, the most common type will be between father and daughter, because the father is beyond the age where familiarity breeds aversion. See M. Daly and M. Wilson, Sex, Evolution, and Behavior (2d ed., Belmont, CA: Wadsworth, 1983).

So there is no rational calculation as to whether to make an alarm call. The analysis suggests instead that ground squirrels would develop an instinct to call alarms when they are near their homes because in general they will be surrounded by multiple close family members and on net it will help the squirrels genes to reproduce. This instinct is merely a tendency, and in fact ground squirrels suppress this instinct when environmental conditions change. First, it is only female ground squirrels who sound alarm calls. This is because in ground squirrel communities males emigrate, while females remain in kin groups. Thus, males tend to be surrounded by individuals with whom they have no genetic relation, thus they become purely interested in their own personal survival. Second, studies have been done of the rare situations where female

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ground squirrels have been forced to emigrate to new groups. Sure enough, these newcomers are less likely than the incumbents to give alarm calls.

Kin selection also explains why ant colonies and beehives have such a high degree of cooperation. Many ants are actually sterile and do not reproduce at all, the ultimate act of individual self-sacrifice. But individual self-sacrifice is not genetic self-sacrifice. Most creatures are diploid for purposes of reproduction, meaning that an offspring requires both a mother and a father for a fertilized egg to reproduce, and therefore draws half her genes from her father and half from her mother, making for a 50% degree of genetic relatedness. Ants, by contrast, are haplodiploid: females are diploid and have two sets of chromosomes (one from each parent), but males arise from unfertilized eggs, thus they only have a mother and have only one set of chromosomes. Unlike most creatures who share a 50% expected genetic relatedness with siblings, ants share an expected 75% expected genetic relatedness with siblings. This high degree of genetic relatedness explains the remarkable social cohesion among ant communities as well as the willingness of individual ants to sacrifice their individual reproduction in order to tend to the feeding and raising of others’ offspring.

The pull of kin selection, for instance, may explain why it is that the law tends not to contractually enforce promises made between family members. See Charles J. Goetz and Robert E. Scott, “Enforcing Promises: An Examination of the Basis of Contract,” Yale Law Journal 89: 1261-1359 (1980). Kin selection suggests that at some base level the utility functions of family members are interdependent, and that, for instance, mothers and fathers will tend not to act opportunistically with respect to their children. As a result, when a family member fails to carry through on a promise, we can assume with a high degree of reliability that the breach was due to a sincere regret contingency and was not merely an opportunistic breach. This analysis will also have implications for rules governing inheritance law and other familial relations.

On the other hand, it has also been argued that the absence of genetic relationships may help to explain the relatively higher degree of abuse of children raised by stepparents relative to those raised by their natural parents. See M. Daly and M. Wilson, Homicide (Hawthorne, NY: Aldine, 1988); Owen D. Jones, “Evolutionary Analysis in Law: An Introduction and Application to Child Abuse,” North Carolina Law Review 1117-1242 (1997). It has been argued that courts should consider such statistical regularities in making child-custody determinations in the event of divorce. See Robin Fretwell Wilson, “Children At Risk: The Sexual Exploitation of Female Children After Divorce,” Cornell Law Review 86(2) (Forthcoming 2000).

Finally, the innate pull to take care of one’s genetic relations has obvious implications for how we think of society as a social organism. It is suggestive of the visceral appeal used in times of war for individuals to pull together with their “brothers and sisters.” It also evidences the folly in some current schemes to break down the family as the basic social unit of society. Kin selection theory suggests that it is the family, even more than the individual, that is the basic social unit of society. Thus, while utopian

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reformers may talk about treating strangers as one’s brothers, this rhetoric really tends to miss the point.

For kin-based altruism to flourish, little is required in the way of conscious action. Also, its payoff in terms of reproductive fitness is quite direct. Unsurprisingly, therefore, kin-based altruism is ubiquitous in nature. In fact, it is often cited as a basic building block of other forms of altruistic behavior.

Cooperation for a Given End

A second form of altruistic behavior is cooperation for a given end, or by-product mutualism. Cooperation for a given end exists when there is some goal that can be best accomplished through a group of individuals working together, rather than acting separately. In such situations there is a payoff from teamwork, so long as it is possible to monitor the members of the team to make sure that contribute to the final output.

Group hunting provides an excellent example of cooperation for a given end. A pack of wolves hunting together, for instance, will be able to capture more and different types of game than the same wolves hunting alone. Similarly a group of hunter-gatherers generally can capture more and larger game than individual hunter-gatherers hunting alone. In this model, therefore, cooperation arises from the self-interest of the various members of the group. Each of the members of the group benefits individually from the larger production that can be generated by hunting together as a team rather than hunting alone. Hunting together, therefore, produces a social surplus relative to what would be produced hunting individually. For instance, assume that five members of a hunter-gatherer band could, hunting alone, capture one rabbit apiece (five total), but that no single individual could bring down a woolly mammoth. Assume further that if the five individuals worked together, they could kill a woolly mammoth that would provide the food equivalent of eight rabbits. The social surplus from hunting together, therefore, would be the equivalent of three additional rabbits.

But there are also costs that are potentially incurred as a result of cooperation for a given end. Group activity raises the threat of free riding by members of the group. For instance, it may be that it is much more dangerous to hunt woolly mammoths than rabbits. Thus, each individual member of the hunting party will have some incentive to lay back and free ride on the efforts of the other members of the party. This may reduce the probability of slaying the mammoth; at the very least it will allow the coward to capture a share of the social surplus despite his unequal contribution to its production. It is interesting, therefore, that societies predicated on a high degree of group hunting have devised a number of norms and practices designed to limit shirking.

First, food sharing (absent reciprocal relationships, which are discussed below) is limited only to those goods that actually require joint production to be produced. Thus, for instance, fruits and berries are generally collected through female effort. This production requires no team production, thus labor inputs are directly reflected in the amount of food outputs generated. As a result, these food products are generally

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consumed within the family and not shared. Among the Ache of Paraguay, plant food and insect grubs are not shared outside the nuclear family, although meat is. Among the Yora of Peru, on “a fishing trip, everybody shares; back at the camp, food is freely shared only in the family, and at all times meat is more widely shared than vegetables. Thus, while fish, monkeys, alligators and turtles are shared, plantains are hidden in the forest until they ripened to prevent neighbors stealing them.”2 See Matt Ridley, The Origins of Virtue: Human Instincts and the Evolution of Cooperation (New York: Viking, 1996). See also K. Hill and H. Kaplan, “Population and Dry-Season Subsistence Strategies of the Recently Contacted Yora of Peru,” National Geographic Research 5: 317-334 (1989).

Second, group hunting is generally engaged in only when economically efficient. Thus when pursuing small game, animals tend to hunt individually, but when pursuing large game requiring teamwork, animals hunt together. See Dugatkin, Cheating Monkeys at 114-116; D. Scheel and C. Packer, “Group Hunting Behavior of Lions: A Search for Cooperation,” Animal Behavior 41: 697-709 (1991). Fish also tend to forage individually unless their environment requires them to hunt together. For instance, it is impossible for an individual or even a small group of wrasse to penetrate the defenses of a single damselfish. Working together in coordinated action, however, a large group of wrasse can distract and overwhelm the damselfish’s defenses. Thus, it appears that wrasse work together in plundering damselfish eggs but forage separately when coordinated action is not as necessary. See S. A. Foster, “Acquisition of a Defended Resource: A Benefit of Group Foraging for the Neotropical Wrasse, Thalassoma lucasanum, Environmental Biology of Fishes 19: 215-222 (1987); R. J. Schmitt and S. Strand, “Cooperative Foraging by Yellowtail Seriola lalandei (Carangidae) on Two Species of Fish Prey,” Coeia 1982: 714-717. Where teamwork is unnecessary the gains to group hunting are small, but the problems of preventing free riding remain constant. As a result, group hunting will be less common.

Third, unusually good hunters are rewarded with a disproportionately large share of the social surplus. Skilled chimpanzees, for instance, get first choice of the meat from slain prey, as well as retain primary responsibility for distributing the spoils. See Frans de Waal, Good Natured: The Origins of Right and Wrong in Humans and Other Animals (Cambridge, MA: Harvard University Press, 1996). Skilled hunters in primitive human societies are rewarded not only with primary hunting spoils but also with disproportionate sexual favors from women, who often directly exchange sex for meat. See K. Hill and H. Kaplan, “Tradeoffs in Male and Female Reproductive Strategies among the Ache,” in Human Reproductive Behavior (L. Betzig, M. Borgehoff Mulder, and P. Turke eds., Cambridge: Cambridge University Press, 1988); K. Hill and H. Kaplan, “On Why Male Foragers Hunt and Share Food,” Current Anthropology 34:701-706 (1994); for a slightly different argument see K. Hawkes, “Why Hunter-Gatherers Work: An Ancient Version of the Problem of Public Goods,” Current Anthropology 34: 341-361 (1993).

Interestingly, the bulk of this analysis rebuts the traditional myth that primitive societies are socialist in orientation. As discussed below, it is true that they are highly 2 Ridley, Origins of Virtue, p. 101.

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egalitarian in their social arrangements (at least as compared to other species), but this social egalitarianism is often misunderstood as economic socialism. Neither chimpanzee bands nor human hunter-gatherer societies are socialist. I am aware of no human or animal society that has sustained an ethic of unconditional sharing of social surplus for very long. It is true that large game is, in fact, shared. But a good deal of sharing is sharing among kin, which is predicted by the kin-group selection model described above. As to non-kin, animal and human societies universally practice an ethic of conditional sharing. An able-bodied individual who could work but chooses not to has no entitlement to the any amount of the social surplus. Male chimpanzees who attempt to free ride by trying to participate in eating without participating in hunting “tend to receive little or nothing.”3 See also C. Boesche and H. Boesch, “Hunting Behavior of Wild Chimpanzees in the Tai Nation Park,” American Journal of Physical Anthropology 78: 547-573 (1989); C. Boesch, “Cooperative Hunting in Wild Chimpanzees,” Animal Behavior 48: 653-667 (1994). At the very least, those who fail to contribute are given the last pick of any meat available, and this is simply because large game will spoil on the open plains (where refrigerators traditionally have been somewhat scarce). Thus, the effective marginal cost of giving food to shirkers in this situation is zero.

In contrast to this strictness of dealing with able-bodied shirkers, weak and infirm individuals are often accorded special treatment and protection from other members of the relevant society, even in chimpanzee societies. Compassion and sympathy toward those who are unable to help themselves appear to be as much a part of human nature as the unwillingness to feel much sympathy for shirkers who subsequently seek to share in the social product. This may account for the universal tendency to distinguish “worthy” from “unworthy” recipients of charity. [A somewhat similar analysis is provided in Amy Wax, “Rethinking Welfare Rights: Reciprocity Norms, Reactive Attitudes, and Political Economy of Welfare Reform,” Law and Contemporary Problems (Forthcoming Fall 2000)]. We seek to help those who are unable to help themselves, but we are outraged when our charity is exploited by those who could help themselves but choose not to do so. The contextual nature of food-sharing is a theme that I will return to below.

The problem of cooperation for a given end is identical to the problem confronted by an economic firm. See A. Alchian and H. Demsetz, “Production, Information Costs, and Economic Organization,” American Economic Review, 62: 777-795 (1972). Alchian and Demsetz argue that the economic function of a firm is team production. Team production can produce outcomes that are unavailable to uncoordinated individuals working alone. They provide the example of moving a couch: no single individual could do it, but four men can do it easily. Thus, there is social surplus as a result of the team production. The problem is that each individual will have an incentive to “shirk” by not working as hard as the other members of the team. Each member of the team faces the same incentives; thus, unless the shirking problem can be contained, either the couch will not get moved, or it will take more time than it would otherwise, thereby reducing the effective social surplus. Alchian and Demsetz argue that, in response to these incentives, some individual will be designated to be a residual claimant whose primary responsibility 3 De Waal, Good Natured, p. 141.

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will be to constrain shirking by the team members. In return, the residual claimant will be rewarded out of the general social surplus. The economic organization of the firm faces virtually identical opportunities and problems as the wolf pack seeking to bring down an elk.

Cooperation for a given end is an important component of cooperation in nature, but it is limited in its utility to serve as a general mechanism for social coordination. Cooperation for a given end presupposes the existence of some uniform goal that all members of the team seek to attain. Society and economy, however, are characterized by a plurality of ends, not a single uniform end. See F. A. Hayek, The Road To Serfdom (Chicago: University of Chicago Press 1944); Adam Smith, The Theory of Moral Sentiments (Indianapolis: Liberty Classics, 1976). Thus, although cooperation for a given end is valuable in allowing individuals to accomplish their individual goals, it does not provide a general theory for organizing society. See Michael Polanyi, The Logic of Liberty (Chicago: University of Chicago Press, 1951); Todd J. Zywicki, “Epstein and Polanyi on Simple Rules, Complex Systems, and Decentralization,” Constitutional Political Economy 9: 143-150 (1998). At the level of the social abstraction of an economy and a society, the fundamental question is how to coordinate these disparate goals peacefully and efficiently.

The appeal of organizing society so as to accomplish a given goal explains the appeal to many social thinkers of a society and economy at war. During such times, it is argued, individuals suppress their plurality of individual goals in favor of attaining a goal that is good for society generally, namely conquest of the common enemy. After such wars end, however, there is a tendency for this uniformity of vision to falter, and individuals return to their individual purposes. As the foregoing has suggested, this duality is natural. Thus, while the hunt is on, there are incentives for each individual to contribute to the common goal of capturing prey. As soon as the prey is downed, however, each individual quickly turns toward attempting to acquire for himself as much as possible of the common surplus. Evolutionary biology teaches us that selfishness is the norm, but that short-term selfishness can sometimes be subsumed into a joint project. Sometimes this joint project can be protection from a common enemy. See Dugatkin, Cheating Monkeys. In the end, however, where cooperation is for some common goal, each individual participates in furtherance of his self-interest.

Robert Putnam’s book Bowling Alone presents an interesting recent example of the error of viewing all of society as having a common purpose, and as all members of society working cooperating to accomplish this end purpose. See Robert D. Putnam, Bowling Alone: The Collapse and Revival of American Community (New York: Simon & Schuster, 2000). Putnam glorifies the effect of World War II in inculcating a heightened sense of civic responsibility in those who fought the war, a commitment that continued after the war’s conclusion. Putnam relishes “the moral equivalent of war” without the bloodshed and disruption of war.4 Thus, Putnam endorses the role played by the post-war organs of civil society in building a civic-mindedness aimed at solving collective 4 Putnam, Bowling Alone, pp. 275-76.

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problems. In stressing these unifying purposes of civil society, Putnam ignores a second, equally important strand of scholarship on civil society, namely the role of civil society organizations in fulfilling a plurality of individual ends. This strand of analysis, exemplified by scholars such as Hannah Arendt and Ernest Gellner, stress the importance of civil society as serving as a guardian of individual liberty and as a counterweight to the tendency of the state to atomize individuals into democratic rent-seekers and to infantilize individuals into passive recipients of the state’s largesse. See Hannah Arendt, The Origins of Totalitarianism (New York: Harcourt Brace & Company, 1973); Ernest Gellner, Conditions of Liberty: Civil Society and Its Rivals (London: Hamish Hamilton, 1994). A full understanding of the vital role played by civil community in a free society requires understanding that the organs of civilization not only help to build social unity in the sense offered by Putnam, but also to preserve a sphere of personal autonomy and pursuit of a diversity of human ends in the sense identified by Arendt and Gellner.

Cooperation for a given end is relatively common in nature. Where the benefits to coordination for a given end are sufficiently large (such as group hunting) and it is possible to constrain shirking and free riding, the ability to cooperate to accomplish a given end is likely to emerge spontaneously and to become hard-wired in an animal’s instinctive nature. Moreover, such coalition actions tend to arise only where necessitated by the environment, and thus such coalitions can be quite fluid and temporary. More stable coalitions tend to be held together by the glue of reciprocal altruism, where gains are provided over time, rather than the more direct and short-term gains offered by cooperation for a given end.

Reciprocal Altruism

A third basis for cooperation in nature is “reciprocal altruism.” Although termed “altruism,” like kin selection and cooperation for a given end, reciprocal altruism is really rooted in self-interest. But the mutual gains from reciprocal altruism are produced over time rather than through a single interaction, as with cooperation for a given end. In reciprocal altruism an individual provides a benefit for another in exchange for a reciprocal benefit, or the expectation of a reciprocal benefit in the future. Because the benefits are traded over time, however, at the outset one of the individuals must provide a benefit (thereby incurring a cost) in exchange for the mere expectation of a reciprocal benefit. By being the first mover, the party that first incurs a cost for another’s benefit can be said to act altruistically, even though the cost is incurred in expectation of a long-term benefit. Assuming that the expectation is eventually realized, this series of reciprocal exchanges over time is called reciprocal altruism. Robert Trivers, generally credited with identifying the model, defines reciprocal altruism as “the trading of altruistic acts in which benefit is larger than cost so that over a period of time both enjoy a net gain.” See Robert Trivers, Social Evolution (Menlo Park, CA: Benjamin Cummings, 1985); see also Robert L. Trivers, “The Evolution of Reciprocal Altruism,” Quarterly Review of Biology 46: 35 (1971). Frans de Waal similarly observes, “Cost-benefit analyses are the staple of evolutionary arguments. The premise is always that there must be something in it for the performer, if not immediately then at least in the

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long run, and if not for him then at least for his relatives.”5 De Waal defines three characteristics of reciprocal altruism:

1. The exchanged acts, while beneficial to the recipient, are costly to the performer.

2. There is a time lag between giving and receiving.

3. Giving is contingent on receiving.

Because the benefits to the giver of reciprocal altruism are generated indirectly (unlike the direct benefits of kin selection) and over a long period of time (rather than in a relatively discrete transaction, as with cooperation for a given end), a system of reciprocal altruism requires a large number of supplementary psychological and social institutions to develop. On a psychological level, reciprocal altruism requires that those bound up in the reciprocal relationship have sufficient cognitive ability to recognize and remember the degree of their reciprocal relationships with others. On a social level, reciprocal altruism requires sufficient stability of population that the long-term benefits of social cooperation can accrue over time. As de Waal poses the challenge, “Reciprocal altruism differs from other patterns of cooperation in that it is fraught with risk, depends on trust, and requires that individuals whose contributions fall short be shunned or punished, lest the whole system collapse.”6 Because of the huge number of supplementary psychological and social institutions necessary to run a system of reciprocal altruism, this form of cooperation is relatively rare in nature, being confined to only the “brainiest” and most social of animals. Again the analysis turns on the relative benefits and costs of this form of cooperation relative to others.

The benefits of reciprocal altruism are potentially large. A system of reciprocal altruism potentially creates huge social surplus to be captured by the society. By allowing trade over a period of time, reciprocal altruism opens up the possibility of a division of labor and credit-based relationships. These innovations make possible the recognition of the gains from specialization, comparative advantage, and the insurance and risk-shifting elements of inter-temporal trade. More fundamentally, absent the possibility of reciprocal altruism, every interaction between strangers would be essentially a one-shot prisoner’s dilemma game, with mutual defection as the dominant strategy. Of course, as the foregoing has indicated, a failure to solve the problem of reciprocal exchange would not mean the end of all cooperation – kin-based cooperation and some degree of cooperation for a given end would continue. So, for instance, a sex-based division of labor (presumably driven by kin-based cooperation) is universal in human societies and is not likely to be the result of mere norms working alone. See Donald E. Brown, Human Universals (New York: McGraw-Hill, 1991). Cooperation for purposes of accomplishing a given goal might also be possible, but even this may break down if there is some need to devise a system of cooperation outside of the joint project (such as how to divide the

5 De Waal, Good Natured, p. 24. 6 De Waal, Good Natured, p. 24.

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surplus of the group activity, i.e., how tigers will divide an impala carcass if there is not enough for each to eat to satisfaction).

But reciprocity opens the possibility of social surplus on a scale unimaginable for kin-based and by-product cooperation. See Robert Wright, Nonzero: The Logic of Human Destiny (New York: Pantheon Books, 2000). Indeed, Matt Ridley has argued that what makes human beings unique is the division of labor, which allows for maximum realization of gains from trade and reciprocal relations. See Matt Ridley, The Origins of Virtue: Human Instincts and the Evolution of Cooperation (New York: Viking 1996). For instance, if six hunters establish an arrangement to share food over time (allowing for temporarily unlucky hunters and lucky hunters to share together), it is estimated that they will reduce the variance in their food supply by eighty percent relative to hunters who do not share their game. The ability to trade different types of products (rather than just trading meat inter-temporally) opens up the possibility of even greater exchange, such as the possibility of trading axes for spears, or spears for vegetables. One man may be good at fishing and another at hunting; there are clear benefits to trading fish for meat in such circumstances.

As noted, however, reciprocal altruism raises a classic prisoner’s dilemma. If you give me meat today, how do you know that I will give you meat next week when I am the lucky one? Wouldn’t I be better off to take your meat today and stiff you when you come open-handed next week? If so, then you will be unwilling to share with me today. The classic prisoner’s dilemma problem of mutual defection seems to prevail.

Of course, it is now known that this analysis is too facile. Once the possibility of repeated interactions in the prisoners’ dilemma scenario is introduced, then it is possible for cooperation to result from these interactions. A stable cooperative outcome can result if the gains from long-term interactions exceed the gains to one party from a one-shot defection of acting opportunistically toward the trading partner. Although a number of scholars hit upon this analysis at approximately the same time in the late 1970s and early 1980s, the most famous was probably Robert Axelrod, who popularized the notion that the “repeat” or “iterated” prisoners’ dilemma provides a cooperative solution to the prisoners’ dilemma game. Axelrod famously ran a computer game where he determined that the optimal strategy to play in such a game was one of “tit for tat,” where the player cooperates so long as his trading partner cooperates, then punishes those who defect. See Robert Axelrod, The Evolution of Cooperation (New York: Basic Books, 1984). It may be less well-known to readers of this article that Axelrod wrote a subsequent article with biologist William D. Hamilton (the “inventor” of kin-selection, as discussed above) where they ran the same experiment to study evolutionary systems. See Robert Axelrod and William D. Hamilton, “The Evolution of Cooperation in Biological Systems,” Science 211: 1390-1396 (1981); reprinted in Axelrod, The Evolution of Cooperation, Chapter 5. Rather than accumulating points, as in the first game, this time Axelrod and Hamilton’s players accumulated “offspring” who were “genetically programmed” to play the same strategy as their “parents.” Thus, successful strategies would reproduce more rapidly than unsuccessful, leading to more offspring over time. Playing the game in evolutionary time, Axelrod and Hamilton discovered that tit for tat was again the optimal

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strategy to play, leaving the most genetic offspring. This suggests that there would an evolutionary benefit for those who develop a natural tendency to engage in guarded cooperation of the tit for tat strategy. Moreover, once established, tit for tat is an “Evolutionary Stable Strategy,” or “ESS,” meaning that it cannot be invaded by a small group of outsiders playing some other strategy. Given the ease with which tit for tat can arise in a community, as well as its “robustness” and adaptability in a wide variety of evolutionary contexts, Axelrod and Hamilton suggest that it is likely that human beings have evolved a natural predilection to engage in guarded cooperation of the tit for tat variety. This hard-wired predilection toward cooperation stands in sharp contrast to the always-defect advice of the Hobbesian worldview that has dominated liberalism for centuries. Subsequent investigators have questioned Axelrod’s conclusion that tit for tat is the optimal evolutionary strategy, instead proposing refinements to tit for tat, such as “Pavlov” and “Firm-but-fair.” Although these variations question whether tit for tat is a uniquely best strategy in the repeat prisoners’ dilemma situation, they are sufficiently similar to tit for tat so as to reinforce the conclusion of the evolutionary value of pursuing a strategy of guarded generosity.

The instinctive nature of reciprocal altruism is illustrated by vampire bat societies. Vampire bats must eat every 48-60 hours or perish. Vampire bats feed on the blood of cattle and horses. These mammals are wary and large enough to brush off bats if they are noticed. Thus, substantial skill is required for a bat to locate prey and to successfully feed. In fact, on any given night, a large percentage of bats (especially young bats) will be unsuccessful in feeding, which would lead to a large number of deaths. To guard against this eventuality, vampire bats have devised a network of relationships where successful bats on any given night share excess blood with unsuccessful bats. Although much of this is sharing between kin, a substantial amount of sharing is between non-related bats.

Sharing among non-related bats appears to be driven by reciprocal altruism, or more specifically, a tit for tat relationship. Any given bat is more likely to share with a bat that has shared with him in the past than a mere stranger. Stingy neighbors are later rebuffed. See Gerald S. Wilkinson, “Reciprocal Food-Sharing in the Vampire Bat,” Nature 308: 181-184 (March 8, 1984). Successful bats have an ability to detect which bats are most in need of blood, and hence share with them first. This maximizes the marginal benefit to the recipient bat and minimal marginal cost to the donor. More importantly, it turns out that vampire bats have an uncanny ability to recognize one another as individual bats. This is essential for reciprocity to prevail, as it enables bats to discriminate among one another in deciding to whom to donate food. Thus, it is also not surprising that for their size, vampire bats have unusually large neocortex regions of their brains. The neocortex region of the brain is responsible for processing information relating to social arrangements, such as the reciprocal relationships described. Humans, of course, have tremendously large neocortex regions relative to our body sizes, reflecting the complexity of our interpersonal and social relationships. In fact, a significant proportion of our brain’s resources are devoted to the task of recognizing individual faces. Ridley, Origins of Virtue, at 69. Vampire bats also have relatively long lifespans and a relatively low degree of social out-migration. As will be discussed below, these

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social conditions also help to sustain a system of reciprocal altruism. As Matt Ridley sums up Wilkinson’s research, “Wilkinson found that [the bats] seem to play Tit-for-tat. A bat that has donated blood in the past will receive blood from the previous donee; a bat that has refused blood will be refused blood in turn. Each bat seems to be quite good at keeping score.... Reciprocity rules the roost.”7

Given the immense benefits offered by reciprocal trade, why isn’t it ubiquitous in nature? In addition to vampire bats, reciprocal relationships have been identified in species as diverse as vervet monkeys, sea bass, fig trees and fig wasps, baboons, chimpanzees, dolphins, and whales. As suggested above, the main reason is that it is costly to run a system of reciprocity, both psychologically and socially. In general, it is only the brainiest species that have sufficient cognitive capacity to remember not only individual identities, but to associate discrete patterns of sharing with each individual. Moreover, the brain is an extremely expensive organ to run in terms of caloric consumption. Thus, large brains will tend to evolve only where sufficient environmental forces require them to do so. In general, only highly social species such as chimpanzees, dolphins, and whales have sufficiently complicated social structures to require large brain capacities.

In addition to requiring sufficient cognitive power, reciprocal altruism requires specific social conditions to prevail. Reciprocal altruism requires that individuals will interact repeatedly and over long periods of time. The benefits of long-term interaction are sufficiently large to reward long-term cooperative behavior and also make it possible to punish those who do not cooperate. In turn, this requires a relatively small and stable social group characterized by repeat interactions among the members of the group. The relationships of the group must be largely egalitarian, thus making it feasible for one individual to punish another. In a highly hierarchical society, it may not be possible for a subordinate to punish someone who is higher-ranked in the dominance hierarchy. Life spans must also be such that the “shadow of the future” is sufficiently long for parties to garner the mutual benefits of long-term reciprocal relations. Finally, long-term parental care and extensive relationships with relatives encourage the development of reciprocal altruism; the presence of cooperation with kin relations provides a “core” group of cooperation that can allow reciprocal cooperation to spread to unrelated individuals.8

Few creatures will meet the three conditions necessary for reciprocal altruism to flourish: (1) sufficient benefit from reciprocal altruism in light of one’s environment, (2) sufficient cognitive capacity to process the information necessary to maintain a system of reciprocity, and (3) the long-term, egalitarian, stable social relationships sufficient to maintain reciprocal relationships. On the other hand, humans appear to be uniquely well-suited to developing reciprocal altruism. “During the Pleistocene, and probably before,” Trivers writes, “a homonid species would have met the preconditions for the evolution of reciprocal altruism; for example, long lifespan, low dispersal rate, life in small, mutually dependent and stable social groups, and a long period of parental care leading to

7 Ridley, Origins of Virtue, p. 63. 8 Trivers, Social Evolution, p. 386-87.

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extensive contacts with close relatives over many years.”9 Moreover, early human society was also highly egalitarian, making reciprocal benefits and punishments available to all. As Matt Ridley states Trivers’s point, “Of all the species on the planet most likely to satisfy the criteria of prisoners’ dilemma tournaments – the ability to meet repeatedly, recognize each other and remember the outcomes of past encounters... – human beings are the most obvious. Indeed, it might be what is special about us: we are uniquely good at reciprocal altruism.”10

This analysis suggests that like other animals, humans may have a “reciprocity instinct,” a hard-wired predilection for cooperation combined with the development of psychological skills and social and cultural norms designed to reinforce this reciprocity instinct. As noted, reciprocal altruism is evident in some animals, and humans have the requisite biological and social organizations that make humans fertile for planting the seeds of reciprocal altruism. In addition, it appears that the tendency toward reciprocity is universal, not culture-specific. For instance, my research has uncovered no culture or religion where it is morally neutral to file bankruptcy and default on one’s financial obligations. See Todd J. Zywicki, “The Reciprocity Instinct: An Evolutionary Analysis of Norms, Promise-Keeping, and Bankruptcy Law” (working paper, George Mason University School of Law, October 28, 1999). Like the incest taboo, the universal nature of the anti-bankruptcy promise-keeping norm suggests that the norm may in fact be a hard-wired product of natural selection and the psychological modules necessary to operate a society on the principle of reciprocal altruism.

If humans do, in fact, have a reciprocity instinct, the consequences of this insight are profound. In particular, it suggests that the recent interest in “norms” theory in legal scholarship is incomplete. See Eric A. Posner, Law and Social Norms (Cambridge: Harvard University Press, 2000); Robert C. Ellickson, Order Without Law: How Neighbors Settle Disputes (Cambridge, MA: Harvard University Press, 1991); Richard H. McAdams, “The Origin, Develoment, and Regulation of Norms,” Michigan Law Review 96: 338-433 (1997). To be sure, these scholars are correct in identifying the strong tendency humans exhibit to establish voluntary and spontaneous norms to resolve potential disputes arising from day-to-day interactions. But their emphasis on the social construction and transmission of norms is incomplete. The foregoing discussion suggests that a theory of norms is flawed without accounting for the hard-wired tendencies of human beings to generate reciprocal relationships. Indeed, it is striking that most important norms are largely universal, and only slightly context-dependent. This includes such things as telling the truth and keeping one’s promises, as well as emotions such as love, friendship, compassion, vengeance, and the like. See Donald E. Brown, Human Universals (New York: McGraw-Hill, 1991). Absent compulsory control, human behavior is a combination of a hard-wired reciprocity instinct combined with cultural norms. It is striking, however, that vampire bats, sea bass, and chimpanzees all exhibit promise-keeping and reciprocal relationships without any social norms instructing them to do so. An evolution-based model of reciprocity also avoids the problem of having to

9 Trivers, Social Evolution, p. 386. 10 Ridley, Origins of Virtue, pp. 83-84.

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develop complicated and fairly implausible models of norms-internalization that fail to explain the presence of reciprocal behavior in non-human species, in children, and in cross-cultural interactions. For instance, Robert Frank has observed that most of the signals used to determine one’s reliability in a social context are actually involuntary. See Passions Within Reason: The Strategic Role of Emotions (New York: Norton, 1988). For instance, an attempt to lie about the truth is generally met with an involuntary blush, stammering speech, and shifty eyes. It is hard to see how these wholly involuntary actions could be triggered a conscious learning about the impropriety of not telling the truth. It is far more likely that we have evolved in such a way as to trigger involuntary physical manifestations of a hard-wired knowledge about the impropriety of lying. Similarly, we seem to have instinctive “truth-detection” skills designed to read individuals to determine whether they are telling the truth. It further appears that the facial expressions that accompany certain emotional states also are universal rather than culture-specific. See Darwin and Facial Expression: A Century of Research in Review (Paul Ekman ed.) (New York: Academic Press, 1973).

In fact, the current state of norms theory is remarkably similar to the state of cultural anthropology a decade or two ago. Fascinated with issues of relativism, cultural anthropologists focused on the task of documenting largely trivial differences between different societies. Introducing evolutionary psychology into the equation has opened a much more important and fruitful examination of the underlying similarities among most cultures throughout the world and throughout history. See The Adapted Mind: Evolutionary Psychology and the Generation of Culture (Jerome H. Barkow, Leda Cosmides, and John Tooby eds.) (New York: Oxford University Press, 1992). This essay is in part an opening attempt to propose a similar approach to norms theorists in the law to ground themselves in a stronger theory of human nature and social evolution.

Group Selection

A final potential path to cooperation is offered by the possibility of group selection. This is the most controversial of the approaches offered here, and most evolutionary thinkers remain highly skeptical of the importance, if not the very concept, of group selection. Nonetheless, recent scholars have argued that the concept is in fact viable, rendering it an empirical question as to whether it has operated in practice. See Elliott Sober and David Sloan Wilson, Unto Others: The Evolution and Psychology of Unselfish Behavior (Cambridge: Harvard University Press, 1998). Despite the skepticism that has generally surrounded group selection, it represents a potentially powerful method for generating social cooperation on a scale exceeding all of the foregoing. Reciprocal altruism is most compelling in providing a theory of cooperation in small-group, face-to-face settings; although it can be extended from these relations of specific reciprocity to general reciprocity on a society-wide basis, this step is tenuous. By contrast, group selection holds out the possibility of encouraging cooperation on a large-scale society-wide basis directly.

Group selection arguments come in two forms, biological group selection and cultural group selection. Although there are differences between the two, the essential

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structure of the argument is similar. Moreover, both cultural and biological group selection arguments have traditionally been attacked on similar grounds. As a result, although there are differences between the two, for purposes of this brief essay I will treat them as largely interchangeable. The analysis presented here summarizes the more detailed arguments presented in Todd J. Zywicki, “Was Hayek Right About Group Selection After All?” Review of Austrian Economics 13: 81-95 (2000).

On its face, the argument in favor of group selection is highly persuasive. Indeed, it is quite common that authors will advance a group selection argument without being fully conscious of having done so. Advocates of biological group selection argue that under certain environmental conditions it may be adaptive on the individual level to develop altruistic traits toward others. Altruism builds trust and reciprocity, thereby reducing the transaction costs of living together in a given society. Greater trust spurs trade, specialization, and the growth of wealth. In turn, this allows for the maintenance of a larger, richer, and healthier population. Such populations will tend to prosper and spread at the expense of less robust populations, leading to the gradual displacement of non-altruistic populations with more altruistic, and causing the altruistic trait to spread. See Sober and Wilson, Unto Others. Cultural group selection arguments are similar, except that rather than propagating one’s genetic traits, natural selection operates on “memes” of rules, customs, institutions, and norms. Groups that adopt “better” cultural practices will again tend to grow healthier, wealthier, and more populous, gradually supplanting less efficient cultures through conquest, migration, or conscious adoption. See F. A. Hayek, The Fatal Conceit: The Errors of Socialism, in The Collected Works of F. A. Hayek (W. W. Bartley, III, ed.) (Chicago: University of Chicago Press, 1988); F. A. Hayek, Law, Legislation and Liberty, Vol. 1: Rules and Order (Chicago: University of Chicago Press, 1973); F. A. Hayek, “The Origins and Effects of Our Morals: A Problem for Science,” in The Essence of Hayek (C. Nishiyama and K. R. Keube, eds.) (Chicago: University of Chicago Press, 1984); Robert Boyd and Peter J. Richerson, Culture and the Evolutionary Process (Chicago: University of Chicago Press, 1985).

Both biological and cultural group selection arguments have been attacked on similar grounds. Although the development of altruistic traits or customs is adaptive on the group level, altruism is not adaptive on the individual level. Because altruism creates social surplus, it is argued, any single individual would do better by acting selfishly rather than altruistically with others. Altruists, therefore, would share with altruists and selfish members alike, whereas selfish members would receive these benefits but would not share with others. Selfish members can thereby free ride on altruists. Over time, it is argued, this would lead to selfish members of society prospering at the expense of altruists, giving selfish individuals a comparative advantage in propagating their genes, and causing those with selfish traits to gradually displace altruists in the population. Thus it is argued that a theory of group selection lacks adequate “micro” foundations in individual reproductive activity to be a sustainable equilibrium theory. See Richard Dawkins, The Selfish Gene (2d ed.) (New York: Oxford University Press, 1989); V. Vanberg, “Spontaneous Market Order and Social Rules: A Critique of F. A. Hayek’s Theory of Cultural Evolution,” Economics and Philosophy 2: 75-100 (1986). For more comment on Hayek’s model of cultural group selection, see D. G. Whitman, “Hayek

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contra Pangloss on Evolutionary Systems,” Constitutional Political Economy 9: 45-66; G. M. Hodgson, “Hayek’s Theory of Cultural Evolution: An Evaluation in Light of Vanberg’s Critique,” Economics and Philosophy 7: 67-82 (1991).

But these criticisms of group selection models overstate their conclusion in implying that group selection is invalid a priori. Like individual natural selection, group selection should be understood as an empirical question, not an a priori question. For group selection to be viable requires the satisfaction of three criteria: (1) benefit to the group from the biological trait or cultural rule; (2) some mechanism for intergroup competition, so that “more fit” groups can displace “less fit” groups; and (3) some mechanism for policing intragroup free riding. See Zywicki, “Was Hayek Right About Group Selection After All?” supra.

First, there must be some benefit to the group from the trait or practice. Beneficial adaptations are those that reduce transaction costs and conflict, and thereby allow for the growth of economic wealth and population. Hayek points to property, contract, and the rule of law as examples of cultural adaptations that would tend to create social benefit and thus be favored by cultural group selection.

Second, there must be some mechanism for intergroup competition to take place. This may be through war and conquest, migration and intermarriage, or conscious adaptation of new practices or institutions.

Third, there must be some mechanism for policing free riding behavior within the group to prevent some individuals from claiming social surplus without contributing to it themselves. This suggests that the type of altruism that would be favored by group selection would be of the “guarded cooperation” described by reciprocal altruism. Thus, it is doubtful that cultural group selection would tend to favor the evolution of psychological traits or cultural practices that permitted unconditional sharing in the social surplus. Rather, group selection would tend to favor altruistic and cooperative behavior, but it would tend to limit this altruism so as to prevent exploitation by unscrupulous free riders. As noted above, it is improper to draw normative conclusions directly from the facts of evolutionary biology. Nonetheless, this tendency toward guarded generosity suggests that socialism and the welfare state rest on an unsound evolutionary foundation. By allowing free riders unlimited opportunity to tap into social surplus, these regimes empower free riders rather than constrain them. See Zywicki, “Was Hayek Right about Group Selection After All?” at 90-93; Paul H. Rubin, “Group Selection and the Limits of Altruism,” Journal of ioeconomics 2(1) (Forthcoming 2000); compare Hodgson, “Hayek’s Theory of Cultural Evolution,” at 79-80 (arguing that cultural group selection leads to a mixed economy). Evolutionary arguments further suggest that individuals may have an innate and culturally reinforced tendency to offer charity and altruism, thereby making compulsory provision of social services unnecessary. Moreover, evolution suggests that voluntarily-provided social services would tend to be provided on a local level and embedded in a network of social connectedness and reciprocal relationships. See David T. Beito, From Mutual Aid to the Welfare State: Fraternal Societies and Social Services, 1890-1967 (Chapel Hill: University of North Carolina Press, 2000). By

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embedding the charitable relationship in this social and reciprocal context, it is likely that this system will be more rewarding and empowering for both the donor and donee. By contrast, it is hard to imagine how natural selection would favor individual preferences that are satisfied through delivery of social services through the inefficient and rent-seeking mechanism of the modern welfare state.

Implications for Social Sciences and Law

Throughout this essay I have attempted to interweave specific examples of types of natural cooperation with implications for social science and the law. It is certainly tenuous to draw specific conclusions from the general observations of evolutionary psychology. In addition to those presented above, this concluding section will add a few thoughts on potential avenues of further research in law and social science.

As suggested above, there has been a recent resurgence in legal scholarship in the concept of norms, or what was formerly know as custom, and the law. This analysis is refreshing, in that it has caused scholars to increasingly look beyond formal legal rules and to the norms and practices that underlie and support legal rules. Individual actors tend spontaneously to develop norms and customs to solve coordination problems as they arise. Properly understood, norms theory reminds lawyers of an earlier era where the law was generally used to buttress and enforce these spontaneously-developed extra-legal norms and customs. See A. C. Pritchard and Todd J. Zywicki, “Finding the Constitution: An Economic Analysis of Tradition’s Role in Constitutional Interpretation,” North Carolina Law Review 77: 409-521 (1999); Robert D. Cooter, “Structural Adjudication and the New Law Merchant: A Model of Decentralized Law,” International Review of Law & Economics 14: 215-239 (1994).

Although important, norms theory only goes halfway. The evolution of norms and customs can only be properly understood within a framework that also includes evolutionary psychology. As noted, there is a huge degree of different types of cooperation in nature that prospers without anything like norms or institutions to enforce them. Evolutionary psychology helps to explain why pro-social and pro-cooperative norms tend to be more prevalent in the world than anti-social and anti-cooperative norms. There is a certain universality to many of the norms that are found throughout the world and even within a given society. Assuming that it is not purely historical accident, this tendency toward universality in the types of norms that develop can be explained in only two ways, either as the result of universal human nature that drives the types of norms that will be developed, or through a system of cultural group selection that allows good practices to drive out bad. As noted, cultural group selection remains controversial in both the natural and social sciences, tending to suggest that evolutionary psychology presents a more compelling explanation. Interestingly, however, the new norms theorists seem to be either unaware of the existence of human universals or largely unaware of the problem of explaining these universals. Just as norms theorists have recognized that norms lie behind law, evolutionary psychologists have long recognized that evolution lies behind norms.

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Law would also benefit from understanding how animals generate solutions to certain social problems. For instance, like humans, social animals are required to deal with the potential problem of internal conflict over scarce resources. Animals, like humans, have devised two basic ways of preventing conflict, property rights and hierarchy. In hierarchical relations, disputes over resources or breeding opportunities are decided by the highest-ranked, or “alpha,” individual in the pack or group. Subordinate individuals must obey the will of the alpha or be punished. Although this social arrangement tends to minimize internal social conflict (except for conflict at the top among rivals for dominance), it also means that the resources of all other members of the society are subject to the will of the dominant and are subject to having those resources expropriated at any time.

More complex societies rely less on hierarchy and more on systems of private property, or territories, to resolve disputes. Territories demarcate specific resources over which particular animals have control. By marking these territories, animals can avoid constant conflict over ownership of resources. Thus, the primary initial impulse for recognizing property rights is to minimize social conflict. Moreover, once property rights are recognized, it is likely that psychological tendencies to retain and protect property rights evolve so as encourage the holder of the property to protect it. Animals and small children exhibit instinctive evidence of property rights and territoriality, suggesting that the desire to claim and protect property is hard-wired. For a fascinating discussion of the instinctive basis of property, see Richard Pipes, Property and Freedom (New York: Alfred A. Knopf, 1999). It seems that concepts of private property, consensual transfer, and protection from involuntary transfer are likely hard-wired in humans and other cognitively-sophisticated and socially-complex creatures. This further suggests that it is an error to see property rights allocations as being merely conventional and subject to rearrangement at the will of political actors. See Todd J. Zywicki, Book Review, Constitutional Political Economy 8: 355-359 (1997) [reviewing Cass R. Sunstein, Legal Reasoning and Political Conflict (1996)]. Allowing individuals to plunder others’ property rights and to acquire economic resources through use of rent-seeking and political force, by contrast, can be understood as a reversion to the political and economic structure of hierarchy.

Evolutionary psychology also has potentially revolutionary implications for political science. Since the publication of James Q. Wilson’s superb book The Moral Sense (New York: Free Press, 1993), a handful of political scientists have attempted to understand the implications of evolutionary psychology for the study of politics. Straussian thinkers have been particularly attracted to understanding the implications of evolutionary psychology for political behavior, probably because of the robust view of human nature offered by evolutionary psychology and the potential of constructing natural law from human nature. Roger Masters was perhaps the most aggressive early exponent of the importance of evolutionary psychology and human nature for a proper understanding of politics and society. Beginning really with The Nature of Politics (New Have: Yale University Press, 1989), Masters published a series of articles and papers designed to spell out his view of the implications of evolutionary psychology for politics. In addition to The Nature of Politics, Masters also wrote such interesting and provocative

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works as Beyond Relativism: Science and Human Values (Hanover, N.H.: University Press of New England, 1993) and edited with Margaret Gruter the pathbreaking collection of essays The Sense of Justice: Biological Foundations of Law (Roger D. Masters and Margaret Gruter eds.) (Newbury Park, Calif.: Sage, 1992).

In recent years Larry Arnhart has carried forward the Darwinian research program in political science. Building on an Aristotelian foundation, Arnhart has explicitly advocated an evolutionary understanding of human nature and a politics . Arnhardt’s exposition can be found in his challenging book, Darwinian Natural Right: The Biological Ethics of Human Nature (Albany, NY: State University of New York Press, 1998). The general thrust of Darwinian-influenced political thinking also is surveyed in Arnhardt’s earlier article “The New Darwinian Naturalism in Political Theory,” American Political Science Review 89: 389-400 (1995). Francis Fukuyama has similarly argued for the relevance of evolutionary psychology for understanding politics and social policy. See The Great Disruption: Human Nature and the Reconstitution of Social Order (New York: Free Press, 1999).

A common strand in the Straussian view of evolutionary psychology and politics is the emphasis on innate human inequality of abilities and character as well as an Aristotelian belief in the inherently “political” nature of man. Both of these arguments have important implications for those interested in political science and political theory. Contrasting with this emphasis on natural inequality is the work of Christopher Boehm, who has stressed the concept of “reverse dominance hierarchy” in human societies. Master and Arnhardt stress the continuity of humans with lower animals and see humans as exhibiting a tendency toward hierarchical social and political relations. Boehm, by contrast, stresses the egalitarian tendency of humans in contrast to hierarchy. Boehm is a democrat and sees human political societies as characterized by fluid social and political arrangements rather than rigid status hierarchies. Boehm’s scholarly output has been prodigious; most relevant for current purposes is his most recent book, Hierarchy in the Forest: The Evolution of Egalitarian Behavior (Cambridge, MA: Harvard University Press, 1999). Boehm’s insights have been largely untapped by political scientists, but it seems that his emphasis on social and political egalitarianism raises questions about the Straussian emphasis on inequality as the basis for political society. Indeed, Boehm’s insights may even be relevant to an understanding of such mundane observations as the public’s tendencies to support anti-establishment “outsider” political candidates such as John McCain and its attraction to populists and political underdogs.

Finally, no discussion of the relevance of evolutionary psychology for politics would be complete without mentioning Frans de Waal’s masterpiece Chimpanzee Politics: Power and Sex Among Apes (London: Jonathan Cape, 1982). De Waal’s extensive study of the social and “political” relations among chimpanzees tells a Shakespearean tale of political interactions and coalition-forming that strikingly illustrates the political processes of primates further up the evolutionary ladder.

The belief in the inherently “political” nature of humanity is also open to debate. In making this argument, one must be careful to distinguish humans’ inherently political

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nature from humans’ inherently social nature. Although individuals are naturally social and enthusiastic about egalitarian reciprocity-based interactions, this type of interaction is distinct from political interactions. There is little reason to believe that politics has anything to do with a desire to seek “the good” or the “public good.” Instead, politics is primarily about the expropriation of wealth by politically powerful coalitions or individuals. Thus, while individuals may be naturally inclined to use political power to further their own ends, it is doubtful that this sort of behavior should be encouraged. Instead, it would seem to make more sense to try to tame this expropriative behavior through constitutions and political institutions designed to discourage the use of the political means of acquiring wealth and instead channel wealth-acquisition into positive-sum market exchange. See Mark Grady and Michael McGuire, “The Nature of Constitutions,” Journal of Bioeconomics 1(3): 227-240 (1999); Todd J. Zywicki, “The State of Nature and the Nature of the State: A Comment on Grady and McGuire,” Jounral of Bioeconomics 1(3): 241-261 (1999).

The insights of evolutionary psychology also cast a powerful influence over the study of economics. Economists generally taken personal preferences as “given.” Evolutionary psychology presents one avenue for understanding individual preferences. Moreover, it suggests that many such preferences, such as the desires for wealth and status, are hard-wired predilections that are relatively unresponsive to changes in relative prices. Of course, what qualifies as wealth or what activities generate high social status may differ according to different temporal and cultural forces. Nonetheless, the basic impulses are relatively constant over time and independent of particular social or economic contexts. This casts doubt on the belief that preferences are primarily socially constructed and that they therefore can be changed through the moral force of law or changes in norms. Vernon Smith, Kevin McCabe, and other researchers at the University of Arizona have been using the tools of experimental economics to make predictions about individual preference functions based on insights drawn from evolutionary psychology. All of their work on this topic is fascinating and important. Good introductions to their experimental approach and some of the conclusions they draw from their research can be found in Vernon L. Smith, “Property Rights as a Natural Order: Reciprocity, Evolutionary and Experimental Considerations,” in Who Owns the Environment? 55-80 (1998); Elizabeth Hoffman, Kevin McCabe, and Vernon Smith, “Behavioral Foundations of Reciprocity: Experimental Economics and Evolutionary Psychology,” Economic Inquiry 36: 335-355(1998); Kevin A. McCabe, et al., “Reciprocity, Trust, and Payoff Privacy in Extensive Form Bargaining,” Games and Economic Behavior 24: 10-22 (1998).

In time, evolutionary psychology is likely to exert its greatest influence in the field of economics. Evolutionary psychology reinforces the economist’s emphasis on methodological individualism and self-interest as the foundations of analysis in the social sciences. Thus, rather than merely assuming the primacy of self-interest, economists can ground this postulate in human nature. See Zywicki, “Nature of the State.” In so doing, evolutionary psychology also tends to justify the emphasis of the public choice school on building political systems on the basis of self-interest rather than public beneficence. Perhaps most interesting, evolutionary psychology holds out the possibility of looking

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into the “black box” of individual preferences to try to understand the structure of consumer preferences, and in particular, why some preferences may be more or less elastic and responsive to incentives and relative prices than other preferences.

The two earliest expositors of examining economics through the lens of biology were Jack Hirshleifer, see Jack Hirshleifer, “Evolutionary Models in Economics and the Law: Cooperation versus Conflict Strategies,” Research in Law & Economics 4: 1-60 (1982); and Gordon Tullock, see The Economics of Non-Human Societies (Tucson, AZ: Pallas Press, 1994). In addition to Smith, McCabe, and the others at the University of Arizona, many contemporary economists are working in the evolutionary tradition, most notably Nobel Laureate Douglas North. Others include Adam Gifford, see “Being and Time: On the Nature and the Evolution of Institutions,” Journal of Bioeconomics 1(2): 127-149 (1999); Hebert Gintis, Game Theory Evolving (Princeton, N.J.: Princeton University Press, 2000); and Paul Rubin, who has written several illuminating articles applying evolutionary psychology to economics. This proliferation of research has coalesced into the study of “bioeconomics” with its own society (the International Society for Bioeconomics) and journal (the Journal of Bioeconomics). The Journal of Bioeconomics is co-edited by Janet Landa, an economist, and Micahel T. Ghiselin, an evolutionary biologist.

Conclusion

This essay is not intended to be comprehensive. It has attempted to state the case why those interested in law and social science should be aware of developments in evolutionary psychology. It has also provided a broad overview of the “four paths to cooperation” that have been identified for understanding cooperation in nature. Finally, it has offered some scattered thoughts on future research ideas for those interested in combining interests in evolutionary psychology and classical liberalism to build a research agenda in the social sciences. Great opportunities remain in almost every field of the social sciences to carry forward the insights of evolutionary psychology to challenging and important research agendas.

Further Research

There are a number of research sources for those interested in further exploring the links between evolutionary psychology, law, and social science. An early pioneer that continues to hold regular meetings and seminars is the Gruter Institute for Law and Behavioral Research, an organization established to advance the study of evolutionary biology and its relevance to law and politics. Information about the Gruter Institute can be found at <http://www.gruterinstitute.org>. A more recent addition is the Society for the Evolutionary Analysis of Law (SEAL), which can be found at <http://www.sealsite.org>. Included on the SEAL is an extensive bibliography listing primary works in evolutionary psychology as well as articles by legal scholars applying evolutionary psychology to law. Finally, there is a loose-knit group known as the Network on Norms and Preferences, an interdisciplinary coalition of scholars investigating the implications of evolutionary psychology for the social sciences. This

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group includes such notables as Herb Gintis, Rob Boyd, Paul Romer, and Dan Kahan. A web site for the Network on Norms and Preferences with extensive links to research in the field can be found at <http://www.unix.oit.umass.edu/~gintis/>. An additional useful site for research is the Center for Evolutionary Psychology, directed by psychologist Leda Cosmides and anthropologist John Tooby, which can be found at <http://www.psych.UCSB.edu/research/cep/>.