Biologists have long been interested in human aggression, but only recently has attention turned to biological issues of war and genocide (Daly & Wilson, 1986; Diamond, 1992; Green, 1991; Lopreato & Green, 1990). The study of the biology of human behavior is responsible for the shift, as this area of investigation offers evolutionary hypotheses for even the most devastating social behaviors. The attention given these broad social issues may prove to be critical in our understanding of human behavior.