The Scientific Roots of Homosexuality

It’s amazing how many things I get wrong. I was sure UCLA’s new football coach, Jim Mora, was a bad hire. He’s on a short list of national “Coach of the Year” candidates. I was certain a book and movie series about humans, vampires, and wolves would be a bust. And I once mistakenly donated appreciated stock shares that I had held less than a year, thus losing the tax deduction. A “friend” of mine often tells me, in the endearing manner only he can, “You don’t know shit!” Maybe he’s right.

But now, thanks to David P. Barash’s challenging and fascinating short article titled “The Evolutionary Mystery of Homosexuality,” I might be right about something of importance. I’ve long had a hunch that scientists would someday prove that homosexuality has a genetic basis. Who, I wondered, would choose to be such a distinct minority in a still relatively homophobic world? My related prediction is that a few decades from now homophobes will be embarrassed by their anti-gay vitriol. Hope I’m not wrong about that one.

Here are two excerpts from Barash:

1) Nor can we solve the mystery (why hasn’t natural selection operated against homosexuality) by arguing that homosexuality is a “learned” behavior. That ship has sailed, and the consensus among scientists is that same-sex preference is rooted in our biology. Some of the evidence comes from the widespread distribution of homosexuality among animals in the wild. Moreover, witness its high and persistent cross-cultural existence in Homo sapiens.

2) . . . a reasonable summary is that, when it comes to male homosexuality, there is almost certainly a direct influence, although probably not strict control, by one or more alleles (defined as one member of a pair or series of genes that occupy a specific position on a specific chromosome). Ditto for female homosexuality, although the genetic mechanism(s), and almost certainly the relevant genes themselves, differ between the sexes.

Beyond the suggestive but inconclusive search for DNA specific to sexual orientation, other genetic evidence has emerged. A welter of data on siblings and twins show that the role of genes in homosexual orientation is complicated and far from fully understood—but real. Among noteworthy findings: The concordance of homosexuality for adopted (hence genetically unrelated) siblings is lower than that for biological siblings, which in turn is lower than that for fraternal (nonidentical) twins, which is lower than that for identical twins.

Gay-lesbian differences in those outcomes further support the idea that the genetic influence upon homosexuality differs somewhat, somehow, between women and men. Other studies confirm that the tendency to be lesbian or gay has a substantial chance of being inherited.

Consider, too, that across cultures, the proportion of the population that is homosexual is roughly the same.

Given some conservatives rejection of global warming data, this research will not cause a collective epiphany on the right. Many on the right will continue to be wary of science and many homophobes will continue to believe that there would be fewer gay men if more households were headed by strong fathers, that gayness will spread if we extend them more civil rights, and that gays and lesbians can be cured of homosexuality through Christian counseling.

On this one, I’m going to side with the scientists and celebrate the progress my gay and lesbian friends are making.

3 thoughts on “The Scientific Roots of Homosexuality

  1. I just have to comment that fraternal twin concordance should be the same as siblings. I don’t understand how it could be more from a genetic view point. Good post though

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