This paper presents a theoretical model for the evolution of same-sex sexual behavior, or homoerotic behavior, in humans. Contrary to the traditional study of the topic, the emphasis is on homoerotic behavior itself, irrespective of sexual orientation. It is an inferential model drawn from cross-species evidence, cross-cultural evidence, and current evolutionary theory. It is posited that humans evolved a disposition for homoerotic behavior because it increased same-sex affiliation among peripheralized hominids and indirectly influenced rates of survival and reproductive success. The implications for the conceptualization of same-sex sexual behavior and future research are indicated.