The Evolution of Human Homosexual Behavior

Abstract

Homosexuality presents a paradox for evolutionists who explore the adaptedness of human behavior. If adaptedness is measured by reproductive success and if homosexual behavior is nonreproductive, how has it come about? Three adaptationist hypotheses are reviewed here and compared with the anthropological literature. There is little evidence that lineages gain reproductive advantage through offspring care provided by homosexual members. Therefore, there is little support for the hypothesis that homosexuality evolved by kin selection. Parents at times control children's reproductive decisions and at times encourage children in homosexual behavior. There is therefore more support for the hypothesis of parental manipulation. Support is strongest, however, for the hypothesis that homosexual behavior comes from individual selection for reciprocal altruism. Same-sex alliances have reproductive advantages, and sexual behavior at times maintains these alliances. Nonhuman primates, including the apes, use homosexual behavior in same-sex alliances, and such alliances appear to have been key in the expanded distribution of human ancestors during the Pleistocene. Homosexual emotion and behavior are, in part, emergent qualities of the human propensity for same-sex affiliation. Adaptationist explanations do not fully explain sexual behavior in humans, however; social and historical factors also play strong roles.

The definition of mental disorder: evolving but dysfunctional?

“…Recent theories argue for homosexuality as an adaptive trait. Kirkpatrick gives the following examples12: the ‘kin-selection hypothesis’ explains homosexuality in evolutionary terms as an altruistic foregoing of reproduction conducive to raising relatives’ offspring. The ‘parental-manipulation hypothesis’ explains homosexuality as selection by the parents of only some offspring to reproduce in order to confer greater advantage upon fewer grandchildren.…”

Living with Stigma and Managing Sexual Identity: A Case Study on the Kotis in Dhaka

“…Why people become homosexual has been a big question. Kirkpatrick (2000) showed that there are three major reasons behind that. Genes are the first according to him, Individuals who identify themselves as homosexual or bisexual are found in particular family lines.…”

Homosexual behavior in wild Sumatran orangutans (Pongo pygmaeus abelii)

“…Homosexual behavior forms part of the sexual or sociosexual repertoire of a large array of primate species [Vasey, 1995;Kirkpatrick, 2000]. For species in which homosexual behavior is observed in the wild, its frequency of expression ranges from rare to common.…”

“…Humans are the only primate species in which individuals form homosexual pair bonds to the exclusion of heterosexual behavior [Kirkpatrick, 2000]. In other Great Apes, with the exception of the bonobo (Pan paniscus) [Kano, 1992], homosexual behavior is infrequently reported from wild populations.…”