Contest Competition for Mates and the Evolution of Human Males

Accumulating evidence suggests that the phenotypes of human males were shaped by contest competition, the mode of sexual selection in which mating opportunities are obtained by using force or threat of force to exclude same-sex competitors. Phylogenetic, paleontological, and archaeological data indicate a great antiquity for male-male violence in our lineage, and human males possess a constellation of traits that suggest specialization for contest competition. Relative to females, males exhibit greater stature, muscle mass, strength, speed, aerobic capacity, ability to dissipate exercise heat loads, craniofacial robusticity, pain tolerance, risk-taking, behavioral displays of physical prowess and acuity to the formidability of same-sex conspecifics, outgroup discrimination, and a propensity to participate in dyadic and coalitional violence. Parallel evidence suggests that some characteristics that distinguish hominins from the other great apes increase formidability in fights (e.g., handheld weapons, habitual bipedalism, and proportions of the hand and face) or function to increase perceptions of dominance (e.g., low vocal frequencies). Many of these traits are consistent with having been shaped by contest competition over mates: they develop or elaborate at sexual maturity and predict success in male contests, mating, and reproduction. Although alternative evolutionary explanations for some of these sexually dimorphic traits are possible, the most parsimonious explanation is that they have been preserved by selection because they aided in contest competition among males throughout human evolutionary history. The evolutionary roots of much of the aggression, intolerance, and violence that plagues modern societies may ultimately lie in the selection that shaped our mating system.