Guns, Germs, and Sex: How Evolution Shaped Our Intergroup Psychology

A phenomenon of perennial interest to social psychologists is people's tendency to categorize others on the basis of group membership and to exhibit a preference for members of the ingroup relative to the outgroup. Recent work emphasizing the evolutionary functions of outgroup aggression, exploitation, and avoidance have shed new light on previously observed intergroup phenomena and generated many new empirical findings. We delineate two distinct evolved psy-chologies of intergroup relations and review recent research pertaining to each. One research line (on the psychology of warfare) focuses on the intergroup competition for resources; as we describe below, such competition - and the associated exploitative psychology - is more amplified among men. The other research line (on the psychology of disease avoidance) focuses on the need to avoid contagious disease. Because the threats posed by competitive versus disease-carrying out-groups are qualitatively distinct, the psychological reactions may also be qualitatively distinct.