Evolution & Human Behavior
Volume 30, Issue 1 , Pages 58-65, January 2009

Testing Miller's theory of alleles preventing androgenization as an evolutionary explanation for the genetic predisposition for male homosexuality

Department of Psychology, Center of Excellence in Behavior Genetics, Åbo Akademi University, 20500 Turku, Finland

Received 9 May 2008; accepted 15 August 2008. published online 30 October 2008.

Abstract 

The genetic background of male homosexuality presents an evolutionary paradox, since homosexuality could be considered a reproductive disadvantage. We tested E.M. Miller's (2000) balanced polymorphism explanation, which states that alleles partially preventing androgenization in male fetuses during pregnancy would be associated with a homosexual orientation. Having all the alleles produces homosexuality, while heterosexual carriers with only a few of these alleles instead have a reproductive advantage; that is, they have more traits, which, by controlling for excessive aggressiveness and psychopathy, make them more attractive mates. Pairs of brothers were used to test these assumptions. If homosexuality is due to having all the androgenization-preventing alleles, then heterosexual men with homosexual brothers are more likely to also have some of the these alleles compared to heterosexual men with heterosexual brothers. These two categories were compared on variables related both directly and indirectly to reproductive success, with heterosexual men with a homosexual brother hypothesized to have an advantage on the variables. However, no statistically significant findings in support of the theory were detected. The results were discussed together with alternative explanations.

Keywords: Homosexuality, Evolution, Balanced polymorphism, Reproductive advantage

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 This research was financed by Grant No. 210298 from the Academy of Finland as well as a Centre of Excellence Grant from the Stiftelsen för Åbo Akademi Foundation.

PII: S1090-5138(08)00085-8

doi:10.1016/j.evolhumbehav.2008.08.004

Evolution & Human Behavior
Volume 30, Issue 1 , Pages 58-65, January 2009