“Genetic factors predisposing to homosexuality may increase mating success in heterosexuals”

Posted by Sappho on May 19th, 2014 filed in Sexuality

ZIETSCH, B. P., K. I. MORLEY, S. N. SHEKAR, K. J. H. VERWEIJ, M. C. KELLER, S. MACGREGOR, . . . N. G. MARTIN, 2008 Genetic factors predisposing to homosexuality may increase mating success in heterosexuals. Evolution and Human Behavior 29: 424-433. Here’s the abstract:

There is considerable evidence that human sexual orientation is genetically influenced, so it is not known how homosexuality, which tends to lower reproductive success, is maintained in the population at a relatively high frequency. One hypothesis proposes that while genes predisposing to homosexuality reduce homosexuals’ reproductive success, they may confer some advantage in heterosexuals who carry them. However, it is not clear what such an advantage may be. To investigate this, we examine a data set where a large community-based twin sample (N=4904) anonymously completed a detailed questionnaire examining sexual behaviors and attitudes. We show that psychologically masculine females and feminine men are (a) more likely to be nonheterosexual but (b), when heterosexual, have more opposite-sex sexual partners. With statistical modelling of the twin data, we show that both these relationships are partly due to pleiotropic genetic influences common to each trait. We also find a trend for heterosexuals with a nonheterosexual twin to have more opposite-sex partners than do heterosexual twin pairs. Taken together, these results suggest that genes predisposing to homosexuality may confer a mating advantage in heterosexuals, which could help explain the evolution and maintenance of homosexuality in the population.

4 Responses to ““Genetic factors predisposing to homosexuality may increase mating success in heterosexuals””

  1. WiredSisters Says:

    Maybe people just like having homosexual in-laws?

  2. Sappho Says:

    Joel and I were brought together by our respective gay roommates and ex-roommates, and reached our 26th anniversary this year, so, going by our experience, those homosexual in-laws may make good matchmakers :-).

  3. Marian Neudel Says:

    Among pack animals, it is common for only the alpha male, or only the alpha female, or only the alpha couple, to mate. Everybody else helps out with the offspring, but unauthorized mating can lead to serious or even fatal social consequences. Of course, that’s a more-or-less separate issue from homosexuality–more like enforced asexuality or at least enforced celibacy.

  4. Sappho Says:

    Of course, the extreme version of this is the hive insects (but they turn out to be more closely related to each other than human siblings are, so it’s a better genetic deal for worker bees/ants/etc. than it would be for us).