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"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.