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Evolutionary Psychology and the Social Sciences

                 Evolutionary Psychology and the Social Sciences

    by [1]Todd Zywicki

    From [2]Humane Studies Review Vol. 13, No. 1

    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.

    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, "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 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

    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 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
    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. [4][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, 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

    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 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

    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 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 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'

    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 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

    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 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." [5][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 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." [6][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 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. [7][4]  Thus, Putnam endorses the
    role played by the post-war organs of civil society in building a
    civic-mindedness aimed at solving collective 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 long run, and if
    not for him then at least for his relatives." [8][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." [9][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 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

    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

    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 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
    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."

    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. [11][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 extensive
    contacts with close relatives over many years." [12][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." [13][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, Development, 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 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 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 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

    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 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.

    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

    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

    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 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 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 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," Journal 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 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 Michael
    T. Ghiselin, an evolutionary biologist.


    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


    1. http://www.theihs.org/libertyguide/people.php/50.html
    2. http://www.theihs.org/libertyguide/hsr/index.php#13-1
    3. http://www.chimp-st-and.ac.uk/cultures/database.htm
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    5. http://www.theihs.org/libertyguide/hsr/hsr.php?id=36&print=1#_ftn2
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    8. http://www.theihs.org/libertyguide/hsr/hsr.php?id=36&print=1#_ftn5
    9. http://www.theihs.org/libertyguide/hsr/hsr.php?id=36&print=1#_ftn6
   10. http://www.theihs.org/libertyguide/hsr/hsr.php?id=36&print=1#_ftn7
   11. http://www.theihs.org/libertyguide/hsr/hsr.php?id=36&print=1#_ftn8
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   13. http://www.theihs.org/libertyguide/hsr/hsr.php?id=36&print=1#_ftn10

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