From his time in residence at the University of Chicago to the present, his research interests have focused on the nature and evolution of gender and of gender roles, as well as the nature and evolution of morality, and the connection of both gender and morality to an understanding of how human coalitions can form and avoid the "free rider problem".

More recently, about twenty years ago, he realized that if the human brain is a "wet computer" pattern recognizer, rather than a rational self interest calculator, then that might be how Mother Nature solved the game theoretic "free rider" problem to make human coalitions effective in evolutionary competition.