Living Reference Work Entry

Encyclopedia of Evolutionary Psychological Science

pp 1-3

Date: Latest Version

Alliance Formation Theory


Evolution of human male homosexuality, Evolutionary theory of homosexuality


A theory holding that homosexual behavior in human males derives from selection for behavior that reinforces male alliances.


The incidence of exclusive same-sex sexual preference (exclusive homosexuality) in humans is greater in men than in women and varies across cultures and historical periods (LeVay 2011). The incidence in contemporary Western cultures is estimated to range between 2 % and 6 % (Barthes et al. 2013). Exclusive homosexuality is an evolutionary paradox, because it does not contribute to reproduction; consequently, it is unclear how genes that may contribute to it are inherited and maintained in the population. The trend in theory and research has been to identify a single explanation. However, recently, some authors have made compelling arguments for more complex and multicomponent explanations that involve both ultimate (evolutionary) and proximate (environmental, d ...

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