LA Times on biological traits of gays

 The LA Times ran a story yesterday on scientific studies about gays, trying to find biological / genetic causes. You can read it here.

Things I find quite interesting in the article are as follows: 

Big brothers. Study after study — including one of 87,000 British men published last year — has found that gay men have more older brothers than straight men do. Only big brothers count. Lesbians don’t show such patterns.

The numbers: Each older brother will increase a man’s chances of being gay by 33%, says Ray Blanchard of the University of Toronto, an expert on the “big-brother effect.” That’s not as dramatic as it might sound. A man’s chance of being gay is pretty low to begin with — perhaps as low as 2% (lowered from 10% by researchers in the early 1990s). So having one older brother ups the chance to only about 2.6%.

What it might mean: Psychological influences are probably not at work, because the pattern holds even for gay men who weren’t raised with their older brothers. Instead, the mother’s womb might be key. After giving birth to a boy, her immune system might create antibodies to foreign, male proteins in her bloodstream. Subsequent sons in the womb could be exposed to these “anti-boy” antibodies, which might affect sexual development in the brain.

Accordingly, you’d expect the percentage of gay men in a society to vary depending on demographic differences in family size: One study calculated that a one-child-per-family law would reduce male homosexuality by about 29% from current levels.

Okay, so I already knew about these studies. But they fascinate me nonetheless. Are there fewer gay men in the “only child” generation from China?

Left hand vs. right hand. The hand you use to sign your name might have something to do with what gender you are drawn to.

The numbers: More lefties — or at least more somewhat-ambidextrous folks — crop up in the gay population than among straight people, several studies have shown. An analysis of more than 23,000 men and women from North America and Europe in 2000 found that being non-right-handed seems to increase a man’s chances of being gay by about 34%, and a woman’s by about 90%.

What it might mean: One guess is that different-than-normal levels of testosterone in the womb — widely theorized to play a role in determining eventual sexual orientation — could nudge a fetus toward brain organization that favors left-handedness as well as same-sex attraction.

Another theory is that development of a fetus might be disturbed by factors such as a mother’s illness, steering the fetus into being less than strictly right-handed — and, in some cases, less than strictly heterosexual.

It’s a politically sticky idea, says Qazi Rahman of Queen Mary-University of London. “It’s essentially saying that homosexual preference . . . is some kind of biological error,” he says. (It might tick off the left-handed folks too.)

Or, to spin off of a light little discussion happening over at Anita’s blog, it might be nice to know that a biological “error” (if so it be) is still beyond the control of the fetus who bears the tendencies consequent to such an error, and that, to use a philosophical notion, the impossible cannot be demanded of one on moral grounds. More carefully: if somebody is not free to do x, then it cannot be justifiable to tell that somebody that she is morally obligated to do x. The converse is this: I am not morally responsible for doing something than which I cannot have done otherwise. If left-handedness is an accident of gestation, then I cannot justifiably be morally blamed for being left-handed instead of right-handed.

Since this is a generally accepted moral principle (though with a number of sticking points when it comes to the problem of free will in the context of so-called “hard” determinism), we can extend it to homosexuality, should this study bear fruit. We cannot reasonably (justifiably) call homosexuality ‘immoral’ if the person who is gay is incapable of being otherwise. Hmm. I spot a basic discussion on free will arguments in ethics burbling below the surface, here. (Mayhaps it will emerge soon on the blog? Stay tuned, bat fans!)

On a tangential note: it is interesting to think that my dad is a lefty, my mom a righty, my older brother and I are lefties, and my younger sisters are righties. So with my sisters, did mom’s system fight off the left-handedness in a similar way as they theorize the mother’s system fights off “heterosexual male-ness”? Is this even plausible?

Hair whorl. How does your hair grow? This might reflect your sexual orientation.

The numbers: A 2004 study of nearly 500 men — 272 on Delaware’s Rehoboth Beach, popular with gay men, 200 on a beach without that reputation — found that hair on the heads of men on the gay beach was 3.5 times more likely to grow in a counterclockwise direction. (Scalp hair typically resembles a clockwise-rotating typhoon.)

What it might mean: One theory is that a single gene might influence hair-whorl direction, left-right brain organization and, somehow, sexual orientation. Exactly how it would do all this, however, is anyone’s guess.

The study, although intriguing, suffers from a lack of scientific rigor. The author walked around while on vacation, collecting hair-whorl observations on men from a discreet distance. He didn’t know anyone’s sexual orientation for sure, and didn’t objectively examine any scalps up close. Rahman’s group is attempting to replicate the results in the lab.

Yeah, it is interesting, though I wonder whether this might be salvaged and expanded to women. Hmm. Don’t see that going anywhere soon. “Uh, ‘scuse me, can I study your follicles?” I see some suspicious edging away in the forcast.



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