The Darwinian Social Contract

How can we explain the social cooperation of human beings while recognizing their propensity to selfish behavior?  At least since the ancient Greek sophists, one possible answer to that question has been the idea of a social contract. 

Among modern political philosophers, Thomas Hobbes began one tradition of social contract theory by asking what sort of contract would be accepted by rational egoists to escape the anarchic disorder in a "state of nature."  Proponents of economic game theory and rational choice theory--including philosophers such as John Rawls--have continued that Hobbesian tradition. 

A second tradition of social contract theory was begun by David Hume and Adam Smith who asked how the existing implicit social contract could have evolved.  Charles Darwin added to that Humean/Smithian tradition in explaining how the moral sense could have evolved through biological evolution by natural selection and through cultural evolution by social learning.  Recently, biologists such as John Maynard Smith have extended this tradition in developing evolutionary game theory. 

Brian Skyrms--in his book, The Evolution of the Social Contract (Cambridge University Press, 1996)--continues the tradition of Hume, Smith, Darwin, and Maynard Smith by showing how evolutionary game theory can illuminate issues in social contract theory.

In Chapter 1 ("Sex and Justice") of his book, Skyrms offers a partial explanation of the evolution of distributive justice.  In a simple bargaining game where we must decide how to divide a valued good among selfish individuals, informed rational self-interest would produce an infinity of strategies to solve the problem.  But an evolutionary approach would suggest that under specified conditions that seem realistic the only evolutionarily stable strategy would be the principle of share and share alike.  A crucial condition for this outcome is that there be a natural tendency for "positive correlation," in which individuals interact with others like themselves.  Fair-minded people promote the evolution of justice by dealing with others who share their sense of fairness and avoiding those who are unfair.

In Chapter 2 ("Commitment"), Skyrms shows how evolution might favor commitments to norms in social dealings for making fair offers and punishing unfair offers.  Experiments in "ultimatum games" show that people will punish unfair offers even at some monetary cost to themselves.  This might seem to contradict the theory that people act to maximize their subjective expected utility.  But it is possible that natural selection has shaped the neuroendocrinological systems for moral emotions, so that the utility functions of the human species show a emotional preference for fairness.

In Chapter 3 ("Mutual Aid"), Skyrms explains the minimal conditions for the evolution of mutual cooperation.  A common paradox of utilitarianism, as captured in the "prisoner's dilemma" game, is that individuals acting for their rational self-interest often refuse to cooperate with one another and thus find themselves worse off than if they had acted for the common good.  Evolutionary game theory indicates, however, that Darwinian evolution has favored a tendency to cooperate for the common good.  Once again, the critical requirement is "positive correlation."  If people are inclined to interact with like-minded people, then cooperative people can enjoy the benefits of cooperation with one another and avoid the costs of being exploited by cheaters.  By contrast, cheaters are punished by being ostracized from cooperative groups and forced into self-defeating interaction with other cheaters.  Darwinian theory, therefore, would support one version of Kant's categorical imperative: "Act only so that if others act likewise fitness is maximized" (p. 62).

In Chapter 4 ("Correlated Convention"), Skyrms shows how conventions such as property could arise from human evolution.  Aristotle believed that property was rooted in natural human propensities.  He claimed, for example, that "not taking is easier than giving, since people part with what is their own less readily than they avoid taking what is another's" (p. 76).  Recent experiments in economic psychology confirm this, because they show that people tend to demand a higher price to sell some good that they own than they would be willing to pay to acquire it in the first place.  Like other animals, human beings thus display ownership behavior in which owners fight harder to keep a resource than they would to acquire it.  This is what Maynard Smith calls the "bourgeois strategy" in animal conflicts over resources: if individuals are either owners or intruders in fighting over resources, this strategy would dictate that one should fight hard until seriously injured if one is the owner, while one should first engage in threatening display but then flee from real danger if one is the intruder.  Evolution could have favored such a rule if resources tend to be more valuable to owners than to intruders, or if it is easier for owners to defend their resources than for intruders to take them away.

In Chapter 5 ("The Evolution of Meaning"), Skyrms shows how signaling systems can emerge among human beings and other animals by evolution.  The evolutionary selection of one signaling system over another may be largely a result of chance.  But the evolutionary advantages of communicating information are so great that the selection of some signaling system is strongly favored by the evolutionary process.  Even where a signaling system requires some altruistic risk by the sender (as in giving an alarm call), accurate signaling would be favored where individuals can recognize and punish those who engage in deception.

Students of political philosophy might be led by this book to consider the possibility that a Darwinian view of human nature could support an Aristotelian conception of natural right.  Skyrms shows us how justice, sociality, property, and language might have emerged from a Darwinian social contract as shaped by natural selection in human evolutionary history.  This could confirm Arisotle's claim that human beings are by nature rational and political animals.