In the light of evolution VIII: Darwinian thinking in the social sciences
Darwinian thinking in the social sciences was inaugurated by Darwin himself in The Descent of Man and Selection in Relation to Sex (8, 9). Despite various misappropriations of the Darwinian label, true Darwinian thinking continued in the social sciences. However, with the advent of evolutionary game theory (10) there has been an explosion of Darwinian analysis in the social sciences. And it has led to reciprocal contributions from the social sciences and mathematics to biology. The theory of games had been created (11) as a theory of interaction among rational agents with a (tacit) presumption of common knowledge of rationality. Evolutionary game theory broadened the scope of game theory by removing the rationality assumption, and replacing it with an adaptive dynamics of differential reproduction. Social scientists soon saw that a whole array of other broadly adaptive dynamics of imitation, social learning, inductive reasoning with best response, and so forth, were relevant and could be analyzed with similar tools (12).Evolutionary game theory was brought to the fore by Maynard Smith (10), but its origins go back earlier, even to Darwin himself (8, 9). The idea of an evolutionarily stable strategy of Maynard Smith and Price (13) derives from the “unbeatable strategy” that Hamilton used in his analysis of sex ratios (14). Hamilton’s analysis is explicitly game theoretic. The payoff—in expected grandchildren—of a sex ratio strategy depends of the strategies of all of the rest of the population. This is a playing-the-field game in Maynard Smith’s terminology. Hamilton builds on the reasoning of Fisher (15) in explaining human sex ratios. Under reasonable assumptions, differential reproduction drives the sex ratio toward that empirically observed. Fisher quotes Darwin from the second edition of the Descent of Man (9), where Darwin says that the problem was unsolved. However, in the first edition (8), Darwin gives essentially Fisher’s argument (16). Darwin had, in a way, invented evolutionary game theory. The idea had to wait until the present to come full flower.Evolutionary game theory was initially seen by some social scientists as just a way to provide a low rationality foundation for high rationality equilibrium concepts. A Nash equilibrium is a rest point of a large class of adaptive dynamics. If the dynamics converges to a rest point, it converges to Nash. This may not happen in all games, but it may happen in large classes of games, depending on the dynamics in question.However, another idea from evolutionary biology shows that the dynamical point of view can be more subversive. That is the idea of population structure. Interactions are not always best modeled as random encounters in a large population. There may be correlation, positive or negative, between the strategies that interact. Hamilton (17⇓–19) and Price (20) clearly saw that such correlations lie at the basis of evolutionary explanations of both altruism and spite. Sources of such correlation for humans are central areas of concern for social sciences: interaction on a social network, homophily or heterophily in network formation, reputation and partner choice in repeated interactions, formation and dissolution of groups for collective action, and honest and dishonest signaling. All are discussed in this colloquium.
Proc Natl Acad Sci U S A. 2014 Jul 22;111 Suppl 3:10781-4.