Inter-sexual mate competition: A previously unrecognized factor in the evolution of human mating

Abstract

Inter-sexual mate competition occurs any time opposite-sex individuals engage in romantic/sexual competition over the same target. The existence of bisexual behaviour among humans suggests the possibility of inter-sexual mate competition, but it has never been systematically documented. I address this absence with research in three cultures: Canada, Samoa, and the Istmo Zapotec (Southern Mexico). A mixed-method qualitative design was used to document the presence and characteristics of inter-sexual mate competition, and survey and experimental designs were used to understand its potential consequences. Inter-sexual mate competition is both prevalent and consequential in Samoa and the Istmo Zapotec, where women compete against rival women and feminine males for the romantic/sexual attention of men. In Canada, where male bisexual behaviour is uncommon, inter-sexual mate competition is rare and inconsequential. Evolutionary models of mating systems and dynamics can be improved by recognizing when and why inter-sexual mate competition occurs.