My goal is to contribute to a scientific understanding of human nature, especially by demonstrating the value of evolutionary theory. Current research topics include:

Sex differences in sports motivation

        Due to an evolutionary history of physical competition among males, evolutionary theory predicts that, compared to girls and women, boys and men will possess a much greater motivational predisposition to be interested in sports. Abundant evidence supports this hypothesis. Nonetheless, many scholars, advocacy groups, and the U. S. courts, believe it is falsified by patterns in the contemporary U.S., where females comprise 42% of high school participants and 43% of intercollegiate participants. My colleagues and I have a new paper showing that more sensitive measures of sports participation indicate that American males actually play sports more than three times as much as American females. Furthermore, there is no evidence that this sex difference in sports participation is decreasing over time. Thus, data from the contemporary U.S. actually support the evolutionary hypothesis.

        I have conducted several studies of sex differences in distance running in the U.S. Although the number females that participate in distance running has grown steadily since the 1970s, so that there is no longer a sex difference in participation, there are still roughly three times as many males that run fast relative to sex-specific world class standards. For example, in a typical local 5K road race with equal male and female participation, for every female that finishes within 25% of the female world record, there are roughly three males that finish within 25% of the male world record. This pattern holds robustly for elite and recreational runners. Because relative running performance is an equally strong predictor of training volume (e.g., kilometers/week) in men and women, these patterns indicate, albeit indirectly, that there is a sex difference in willingness to train competitively.  In other words, although the vast majority of distance runners in the U.S. have a primarily non-competitive orientation, the small number of male runners who are truly competitive is about three times as large as the number of truly competitive female runners. This sex difference in motivation has been stable since the early 1980s for elite runners and early 1990s for recreational runners.

Cross-societal variation in girls’ and women’s sports

        An evolutionary perspective predicts that males will, on average, be more interested than females in sports in all or nearly all societies. Nevertheless, evolutionary theory predicts that the magnitude of sex differences will vary across cultures. We recently demonstrated this in a study of the Human Relations Area Files probability sample. For all 50 societies with documented sports, there were more male than female sports. However the sex difference was typically greater in patriarchal than in non-patriarchal societies, where women enjoy greater power.

         We are currently completing a cross-national study of Olympic success. Preliminary results indicate that in nations with greater gender equality, women constitute a larger percentage of a nation’s participants and medal winners. We also hope to test whether, across nations, gender equality predicts sex differences in sports interest and physical fitness.

The representation of evolutionary theory in the social sciences

        Many scholars have suggested that many areas of psychology and other social sciences are dominated the Standard Social Science Model or a Blank Slate conception of human nature. The Blank Slate holds that that the mind is wholly shaped by the environment and that individuals have no inborn mental faculties or predispositions besides the general ability to learn. Although many contemporary scholars deny this extreme position, my colleagues and I are attempting to document its prevalence in textbooks and science papers.

The development of elite athletic ability

        Evolutionary theory holds that behavioral traits and abilities represent interactions between genes and experience, not the exclusive influence of one or the other. Nonetheless, some scholars believe that when it comes to truly elite performance, talent is only an illusion and that only experience matters. We are attempting to test this account by gathering data on the development of elite sprinting ability.