McDonald, M. M., Navarrete, C. D., & Van Vugt, M. (2012). Evolution and the Psychology of Intergroup Conflict: The Male Warrior Hypothesis.
Philosophical Transactions of the Royal Society-Biological Sciences, vol. 367 no. 1589 670-679; doi: 10.1098/rstb.2011.0301
The social science literature contains numerous examples of human tribalism and parochialism --
the tendency to categorize individuals on the basis of their group membership, and treat ingroup
members benevolently and outgroup members malevolently. We hypothesize that this tribal
inclination is an adaptive response to the threat of coalitional aggression and intergroup violence
perpetrated by “warrior males” in both ancestral and modern human environments. Here we
describe how male coalitional aggression could have affected the social psychologies of men and
women differently and present preliminary evidence from experimental social psychological
studies testing various predictions from the “male warrior” hypothesis. Finally, we discuss the
theoretical implications of our research for studying intergroup relations both in humans and
nonhumans and discuss some practical implications.