- Homosexuality shows a reasonably high heritability.
- Research has found that lesbians are inclined toward even less promiscuous lives than heterosexual women.
- Researchers repeatedly find that homosexual men are most attracted to men in their late teens and early twenties, prioritizing looks over status.
When I was 19 years old, the sexual revolution was raging. In New York City, where I grew up, there were “love-ins” in Central Park, and beautiful young women walked around in loose halter tops without bras, apparently proud of their newly liberated sexuality.
One night, I took the subway into Greenwich Village, dressed in my finest bell bottoms and a peacoat, with the brilliant idea that I’d hang out on the street until one of these sexually free beauties picked me up. I stood around awkwardly for a while, but I was finally targeted with the classic pick-up line: “Don’t I know you?”
Instead of a braless young hippie woman with flowing blonde hair, though, my new friend was a middle-aged conservatively dressed Black man. And he seemed surprised when I said: “Yes, you do know me.” As it turns out, the fellow had come by the Paramount hotel, where I was the doorman, a few days earlier, looking for a young basketball player on the New York Knicks (who summered there at the time). Although neither of our fantasies was fulfilled by the encounter, we ended up having an interesting conversation about homosexuality, a topic the fellow was studying in graduate school, with an obvious personal investment, and the topic of a paper I’d written in my undergraduate psychology class.
At the time, the psychological accounts of homosexuality’s causes focused on the relationships between homosexual men and their parents, especially their mothers. Since then, the focus has shifted to biological accounts. For one thing, homosexuality shows a reasonably high heritability—if you are homosexual, and you have a twin brother, there is a very good chance he is homosexual as well.
Three queer things about homosexuality
The first odd thing about homosexuality is the fact that it has such high heritability—how can a proclivity toward having non-reproductive sex be passed on genetically?
Another odd thing about homosexuality is the shape of homosexual men’s preferences: Although gay men share women’s attraction to humans with penises, that’s about as far as the similarity goes. Women are attracted to slightly older men, and women generally prioritize a man’s social status over his physical attractiveness. But studies by Michael Bailey, my own colleagues, and other researchers repeatedly find that homosexual men are most attracted to men in their late teens and early twenties, and they don’t care much about status, instead prioritizing physical attractiveness.
All this suggests that the old “social learning” theories don’t apply well to homosexual preferences—if so, gay guys would learn from media and the social environment what makes for an attractive man, and go after the same features that women find attractive.
The third odd thing about homosexuality is the quantity of homosexual men’s preferences, as compared to those of homosexual women. Homosexual men are famously promiscuous, a fact that became well-known with the onset of AIDS, when studies of gay men who were HIV-positive revealed average numbers of partners in the hundreds (and even though gay men who were HIV negative had much lower numbers, the average for them was still dramatically higher than the average numbers for heterosexual men).
Lesbians might have been expected to be more promiscuous than heterosexual women, since they had no pregnancy to fear, and on the classic theories, would have been inclined to play out a “male sex role.” But research by Michael Bailey and David Schmitt found that lesbians are inclined toward even less promiscuous lives than heterosexual women.
Kinsey and his colleagues found that over a third of men and 13% of the women in their sample had had at least one homosexual experience to orgasm. There were criticisms of Kinsey’s sampling techniques, but later researchers have also found a substantial percentage of the population reporting some attraction to the same sex. For example, a recent study of almost 5,000 twins in Australia found that although only 2.2% of the men and 0.6% of the women were exclusively homosexual, a much larger percentage—13% of men and 11% of women—had at least some sexual experience with, or attraction toward, the same sex.
Given that natural selection works to promote successful reproduction, why is a substantial portion of the population homosexual?
One possibility is that homosexuals traditionally helped their relatives raise their offspring. In a study of homosexual men in a traditional society (Samoa), Vasey and VanderLaan found some support for this hypothesis. This explanation is also consistent with findings that homosexuals are more likely to be later-born children in large families. But studies in modern urban contexts do not support this kin-support hypothesis, perhaps because homosexuals in modern societies tend to move away from family members.
Another possibility is that whatever genes predispose homosexuality carry benefits in their nonhomosexual relatives. Camperio-Ciani and other researchers have gathered some evidence that relatives of homosexuals have more sexual partners, and more offspring, than relatives of a comparable sample of heterosexuals
Two of the puzzling features of homosexuality make some sense if you consider that sexuality is not simply a “one switch” mechanism, but a composite of a number of separate mental modules. Homosexual men are inclined toward promiscuity, attracted to youth and good looks, and uncaring about status—hence many of the sexual switches in homosexual men are set in the same position as they are in heterosexual men—if gay guys were straight, their preferences would lead them to pick fertile females. But they are attracted to men, so one switch is thrown without the others that contribute to heterosexual females' preferences.
The final puzzle about ultimate causal mechanisms is not yet resolved, though. To complicate matters further, researchers like Lisa Diamond have reviewed a reasonable amount of evidence that different explanations will likely apply to male and female homosexuals, and bisexuals. Of course, unsolved puzzles are what make science fun.
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