Gay Men Born Gay
Gay men often claim that even as children they knew they were somehow “different” from other boys. Many say that sense even preceded puberty. And yet, though researchers have tried for decades to identify a biological basis for homosexuality — which seems to be present in all human societies — they have mostly come up dry. Tantalizing clues have surfaced: gays are more likely to be left-handed, for instance.
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But in the end, there has been little proof that biology is sexual destiny. Now new research offers evidence that there may indeed be a physiological basis for sexual orientation. In a study of 41 brains taken from people who died before age 60, Simon LeVay, a biologist at San Diego’s Salk Institute for Biological Studies, found that one tiny region in the brain of homosexual men was more like that in women than that in heterosexual men. “Sexuality is an important part of who we are,” notes LeVay, who is gay. And now we have a specific part of the brain to look at and to study. “
That specific part is found at the front of the hypothalamus in an area of the brain that is known to help regulate male sexual behavior. Within this site, LeVay looked at four different groupings of cells, technically referred to as the interstitial nuclei of the anterior hypothalamus, or INAH for short. Other researchers had already reported that INAH 2 and 3 were larger in men than in women. LeVay hypothesized that one or both of them might vary with sexual orientation as well.
Routine autopsies provided the tissue LeVay needed. All 19 homosexual men had died of AIDS. So had six of the 16 presumed heterosexual men and one of the six women. Although LeVay hoped to include lesbians in his study, he was unable to obtain brains from women identified as such. After careful examination of the brain samples, he found that the INAH-3 areas of most of the women and homosexual men were about the same size. In straight men this region was on average twice as large — or about the size of a grain of sand.
In the past, much research on sexual orientation has focused on the role of interpersonal relationships in early childhood. Psychological literature is replete with material suggesting that male homosexuality is triggered by relationships with an overly protective mother or with a distant, even hostile father. “Here is a whole other way of looking at the question,” says LeVay. “These children may already be determined to become homosexual or heterosexual. The development plan that is laid out for them may be what causes them to develop certain troubled relationships with their parents. LeVay’s findings are certain to trigger a good deal of controversy. Many technical aspects of the study are subject to question, as the author concedes. He cannot be certain, for instance, that all the heterosexual men in the control group were heterosexual.
And since the AIDS virus attacks the brain, the size difference could be an artifact of the disease. It is also possible that the difference actually has nothing to do with sexual orientation or that it is the result rather than the cause of homosexuality. (2 of 3) My freshman biology students know enough to sink this study,” declares Anne Fausto-Sterling, professor of medical science at Brown University. Others are more receptive to LeVay’s work. “It makes sense,” says Laura Allen, a neuroanatomist at the University of California, Los Angeles. Finding a difference in the INAH, which influences male sexual behavior, “is what one would expect. “
The finding also has social implications. “People who believe that sexual orientation is a choice help legitimize discrimination against homosexuals,” says Melissa Hines, a UCLA psychologist. But if it is immutable, or partly so, then that argues for legal protections. ” The new study is the second to find some sort of difference between the hypothalami of gay and straight men. Last year a Dutch research team discovered that another group of neurons in this tiny gland is larger in homosexual than in straight men. But some scientists believe this structure governs daily rhythms rather than sexual behavior, so it is difficult to see any significance in the finding. Investigations of right- and left-handedness have also provided evidence of a physiological distinction.
Sandra Witelson, a professor of psychiatry at McMaster University in Hamilton, Ont. , has found more left-handers among homosexual women in her studies than among heterosexual women. Others have made the same observation among men. Since hand preference may be determined in part by the influence of sex hormones on the brain during gestation, Witelson believes these early hormonal influences could also play a role in sexual orientation. Animal studies provide a good deal of evidence for a biological basis of sexual orientation.
Through careful manipulation of hormone levels in newborn rats, Roger Gorski, a neuroendocrinologist at UCLA, has been able to produce male rodents that demonstrate feminine behavior. Other researchers, working with mice, have noted that female fetuses that develop between two male fetuses in a litter appear to be masculinized to some degree by their brothers’ testosterone. They look more like males than females, mature more slowly, have fewer reproductive cycles as adults and are less attractive to male mice. In many species, particularly among mammals, homosexual-like activity is an integral part of social interaction.
As any cattle rancher can attest, cows frequently mount each other. Apparently this ensures that all the females coordinate their reproductive cycles and then produce their calves at the same time. Female rhesus monkeys mount other females as a way of establishing a dominant rank in their troop’s hierarchy. (3 of 3) Researchers estimate that a third of American males experiment sexually with each other during their teen years, even though approximately 9 out of 10 eventually settle into relationships with girls.
But both men and women may switch gears later on or be bisexual throughout life. “There are some people in whom sexual orientation does not maintain itself,” says June Reinisch, director of the Kinsey Institute for Research in Sex, Gender and Reproduction at Indiana University. “It’s not a matter of what they prefer; it’s whom they fall in love with. ” She cites the example of a woman who fell in love with and was married to a man for 10 years, then at the age of 30 fell in love with a woman and spent 11 years in that relationship, and at 41 fell in love with a man.
Clearly, even if sexual orientation does have a biological basis in the brain, it is not necessarily fixed. “All of us believe that genetic and hormonal influences are involved in homosexuality,” says Reinisch, “but there’s also an interaction with the environment. ” Over the years much research on homosexuality has been motivated by a desire to eradicate the behavior rather than understand, let alone celebrate, diversity.