Male-enforced intergroup hostility predates modern humans in the hominoid line.

Evidence

Considering only closely related primates in the hominoid clade, there are a number of other common and relevant features of social organization, including: (a) the existence of closed social networks or what might be called ingroups, (b) communal territoriality, (c) male domination of intergroup relations, (d) the male domination of hostile and antagonistic relations between groups, and (e) the male domination of stalking, attacking, and of killing outgroup males (Ghiglier, 1989; Wrangham, 1987). This list suggests that the hominoid clade appears to be predisposed towards an ethnocentric orientation in which boundary maintenance towards outgroups is largely enforced by males. — John T. Jost and Jim Sidanius, Political Psychology, 3262 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Men serve as the primary targets and agents of intergroup prejudice; Men are both primary targets and primary agents of out-group hostility — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 1233; Sexual selection makes men primary targets and agents of intergroup aggression. — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 1210 (+5 more)

Broader Connections

• Hominoid primates show an evolutionary predisposition toward male-enforced ethnocentrism. #corroborates (0.95) — John T. Jost and Jim Sidanius, Political Psychology, 3262