The deadliest primate: Contest competition and the evolution of human males

Many human sex differences can be explained by positing an evolutionary past in which males used force or threat against competitors to win mates. We review phenotypic, phylogenetic, archaeological, paleontological, genetic, and other evidence that this form of sexual selection-contest competition-played an important role in shaping men's behaviors, including physical aggression and displays, and anatomical traits, including skeletal dimensions, muscle mass, facial hair, and voices. Contest competition is not mutually exclusive with other putative evolutionary causes such as sexual division of labor, female mate choice, selection on developmentally correlated traits, and phylogenetic inertia, but none of these explains human male phenotypes as parsimoniously. Our review suggests that human ancestors lived in single-male, often polygynous, family units embedded within larger bands and that males used aggression both within and between groups to obtain and defend mates. Although we understand social concerns regarding this perspective, such concerns may bias evaluations of the evidence, ultimately leading to worse outcomes.