Posted by: Chris | October 27, 2010

Pleiotropy and the Gays, Ctd.

Simon LeVay, former Harvard neuroscientist, has some interesting things to say to Salon on about one of our regular topics.  He seems to basically agree that a pleiotropic explanation for homosexuality suffices to explain its prevalence and persistence, citing some of the same evidence as we have:

The usual idea is that a gene predisposing some individuals to homosexuality might promote the reproductive success of others, and the two effects might balance out. It might be that a gene predisposing a man to be gay might make a woman even more attracted to men than she otherwise would be, so that she would engage in more heterosexual sex and thus become pregnant more often. There are a couple of studies reporting that women who have gay male relatives (and who may therefore carry the same “gay gene”) do indeed have more children than women without any gay male relatives. The answer will remain speculative, however, until the actual genes have been identified and their mode of action worked out.

Fortunately, it seems that outside the realm of science writers, fantastical adaptionist narratives do not prevail.  Andrew, despite claiming that the evolutionary rationale for homosexuality is obvious to “for anyone with even a small grasp of evolution and genetics,” seems to have stumbled onto one of the most ill-informed renditions of the gay-uncle/kin-selection non-explanation I have seen:

There is also a socially evolutionary argument, that societies that had a few men uninterested in actually reproducing with women themselves might be advantageous. They might help advance a society’s education, or become spiritual leaders, or be warriors unaffected by the need to take care of a household.

Finally, LeVay also notes that much of what has been written about gay animals is misleading:

Much more common are animals that are to some degree bisexual. They will, on some occasions, mate with same sex partners and, on other occasions, other-sex partners. For example, in bonobos, our oversexed primate relatives, you see all kinds of sexual behavior depending on social circumstances. Animals use sex for purposes beyond reproduction: for forming alliances, swapping sex for material things like food and so forth. And you see same-sex pairing in many bird species.

In breeding colonies of seagull species where there’s an excess of females, you’ll have female/female mating. It’s not really the case that you’ve got individual animals that have a predisposition to be homosexual or heterosexual. It’s a tricky thing to actually find what we call “homosexuality” in the wild, because you really have to follow animals for long periods of time. They’re all having sex with each other, but you’ve got to figure out which of them actually prefer doing that.



  1. […] for the former and benevolent pleitropic and carrier effects for the latter, which also seems to be the dominant view of the relevant scientific community.  However, a post on the issue by Razib Khan and the […]

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