Evolutionary psychology is a research area devoted to explaining human psychology, and ultimately human behavior, through a study of how we evolved as a species. The first question one might immediately ask when informed of the goals of evolutionary psychology is, why bother? If we have a good model of the human mind, how will it help us to understand how it became what it is?
This is a good question to which I do not have a satisfactory answer, although I in fact think that understanding our evolutionary history is a prerequisite to developing insightful models of the human mind. Theodosius Dobzhansky famously said that nothing in biology makes sense except in the light of evolution, and I am certain this is true. But why is it so important that our model of the human mind “make sense?” Isn’t it enough that the model be accurate? Perhaps the answer is that our models of complex adaptive systems are never so accurate and persuasive that they do not benefit from some deep historical perspective. For instance, physicists care about the history of the Universe, and certainly believe that this will not only help “make sense” of physical theories (e.g., the arrow of time, thermodynamics, why we are here), but contribute as well to our formulation of the laws of physics.
Whenever I develop a model of some human behavior, my first question is, “how might this evolved?” My reasoning is that my evidence for the model is not so convincing that it wouldn’t be strengthened by an evolutionary/historical dimension. For instance, I and coauthors (Samuel Bowles, Rob Boyd, Peter Richerson, Ernst Fehr, et al.) have developed models of altruistic punishment that explain many results of laboratory experiments, and help understand everyday life. Surprisingly, this concept does not appear in the psychological literature except in the form of a social pathology, whereas in our model, it is a key and universal behavior that is central to understanding all of human social dynamics. As a result, we have spent a lot of energy modeling how this behavior might have evolved, and why it only has evolved to a high state in humans. We found that the only persuasive models require that altruistic punishment of social wrongdoers be highly socially controlled, rather than spontaneously carried out on an individual level. This insight leads us to include such sophisticated social institutions in the set of core institutions without which human sociobiology cannot be understood.
Conclusion: Although we are not sure exactly why an evolutionary dimension to social theory is necessary, we know it is. Indeed, in my vision of a unified behavioral science, gene-culture coevolutionary theory is the first principle in human sociobiology, playing the same role in the social sciences as physics does in the natural sciences---it is the basic theory in light of which the other theories make sense.
In this sense, my colleagues and I are evolutionary psychologists. However, people often think that in this case, we must subscribe to the theories of the most prominent of the evolutionary psychologists, Leda Cosmides and John Tooby (UC Santa Barbara). Despite my admiration for their work, especially their incisive critique of the Standard Social Sciences Model (Jerome H. Barkow, Leda Cosmides and John Tooby, The Adapted Mind: Evolutionary Psychology and the Generation of Culture (New York: Oxford University Press, 1992), I think the major premises of their brand of evolutionary psychology are wrong. There are two such premises. The first is that the human mind is highly modular, different parts of the brain having developed at different times to meet particular task, so there is no “general intelligence” guiding our actions. The second is that our modern, highly educated and sophisticated minds are housed in “stone-age skulls.” By this, Cosmides and Tooby mean that there are many behaviors we engage in simply because these behaviors were fitness-enhancing in prehistoric times. For instance, we cannot control obesity because the conditions under which we evolved give us urges that entail obesity when the cost of nourishment becomes low and the need for exercise to sustain daily life vanishes.
The story about obesity is probably true, but how many such stories make sense? So many important ones do not that it hard to defend the “modern minds in stone-age skulls” at all. For instance, perhaps the most important fact of modern life is the “demographic transition,” according to which when a society attains a certain level of GNP per capital, the birth rate falls rather precipitously so that the number of children per family surviving to reproductive age declines to a level that at best stabilizes population growth. There are many theories of why this occurs, but the important fact is that we are the only species on this planet that has been observed to abandon maximal exponential population growth when enjoying all its survival conditions---enough to eat, adequate climate, and absences of predators and parasites. This is an absolutely stunning fact. Were it not true, civilization as we know it could not have emerged, as every technological advance would have merely changed the equilibrium population density, while Hobbes’ description of life as solitary, poor, nasty, brutish and short would hold today as it did in our prehistory, where human population growth was approximately zero on average for many tens of thousands of years.
Does “modern minds in stone-age skulls” help us understand gender relations in modern societies? The well-known EvPsych (as the stone-age skulls group is informally known) argument is a strong affirmative. Like all mammals, the human female invests much more in the creation and nurturing of her young than does the male. Indeed, a single male produces enough sperm to fertilize a virtually unlimited number of females, while a human female cannot produce more than about twenty offspring in a lifetime. In this situation, in virtually all non-human mammal societies, including non-human primates, females perform all of the child-care, and males expend great energy in seeking copulations. Moreover, in many species, males jealously guard their mates and are very sensitive to paternity when contributing to the protection and feeding of the young.
Does this not describe human life as well as that of other species? This case has been made eloquently by David Buss in a series of highly publicized books and papers (see, for instance, David M. Buss and Neil Malamuth, "Sex, Power, Conflict: Evolutionary and Feminist Perspectives". Oxford University Press, USA, 1996). The problem with these findings is that our legacy of patriarchy, which is a quite modern institution that may not have existed or been important until the growth of trade settlements and sedentary agriculture some 10,000 years ago, easily explains the same facts. Indeed, the strength of the evolutionary case for gender differences in attitudes towards mating and family commitments is based on statistical regression methodology, which often reports that a variable such as male vs. female is “statistically significant” in predicting attitudes and behavior, while the actual contribution of this variable to the overall incidence of behavioral differences across sexes is extremely small. Indeed, this is often the case when sample sizes are large. What, after all, is important about a variable like “enjoys one-night stands” if this explains only 1 percent of the variation across sexes, despite being “significant” to the 0.001 level in a regression equation. The answer is: nothing.
More important, the stone-age skulls story requires that gender relations be relatively impervious to social change, just as obesity is. In the case of gender differences, however, there has been great narrowing in the United States since the feminist movements of the 1970’s. Consider, for instance, a recent survey of 5,000 young single Americans undertaken by Helen Fisher (Rutgers), Stephanie Coontz (Evergreen State) and Justin Garcia (Binghamton). They found that more young men than young women value love, marriage, and having children, while the reverse was true of valuing independence, “hooking-up (sex without commitment), and one-night stands.
These new findings---and there will be many more in coming years---show that while the problem of modern minds in stone-age skulls is real, the human brain is sufficiently flexible and capable of adjusting to new conditions generated by modern technology and culture. There is no question in my mind but that gene-culture coevolution helps explain central elements of human physiology (e.g., the organs of verbal and visual communication), epistemology (e.g., the ability to understand other minds), and morality, including altruism, character virtues (honesty, considerateness, loyalty, and so on), empathy, insider-prejudice, and sense of justice and retribution. But these basic human cognitive and moral capacities operate so deep in the human psyche that their concrete phenotypic expression is in most cases extremely malleable, although probably not so much that primeval human cognitions and emotions will ever be more than partly trumped by modern culture. In this sense, I am an evolutionary psychologist.