What most influenced LeVay, though, was a 1989 finding by Roger Gorski and Laura Allen, a UCLA team that had studied male-female brain differences in rats for years. "So is the anterior commissure, another nerve pathway between the brain's two halves." (It was recently shown that the anterior commissure is larger in gay men too.) "On the other hand, part of the amygdala-an almond-shaped area near the hypothalamus that plays a role in sexual arousal-is larger in males than in females." "The corpus callosum-the nerve bundle connecting the two brain hemispheres-is relatively larger in females," LeVay points out. Neuroanatomists have documented such sexual dimorphism in brains since the early 1980s. LeVay was by no means the first to find sex-related anatomical differences in the brain. You wonder what made this quiet, unthreatening academic venture into "such a touchy subject," as he calls it. Dressed, as usual, in jeans and an open-necked shirt, his appearance might be described as a precarious equilibrium between natty and rumpled.
He still has the trim body of a competitive bicyclist, which he was for three decades. A soft- spoken, self-effacing man, he stands 5 foot 9, egg-bald except for a short fringe of graying hair that betrays his 50 years. LeVay hardly seems the sort to inspire controversy.
But people get nervous, as if I'm painting gay men as women in disguise." In a brain region regulating sexual attraction, it would make sense that what you see in gay men is like what you see in heterosexual women. Yet what LeVay did say was plenty controversial enough: "I am saying that gay men have a woman's INAH3-they've got a woman's brain in that particular part. But there's no technology right now to image structures as small as INAH3." The experiment one would love to do," he adds, "is to scan newborn children's brains, measure the size of the cell group, and wait 25 years to see how they turn out. The differences I found could have developed after a person was born-a sort of 'use it or lose it' phenomenon-though I doubt it. Although most psychiatrists now agree that sexual orientation is a stable attribute of human personality, my work doesn't address whether it's established before birth. "Since I looked at adult brains," he says, "we don't know if the differences I found were there at birth or if they appeared later. My work is just a hint in that direction-a spur, I hope, to future work."ĭecades of scientific rigor have made caution a habit with LeVay. Nor did I locate a gay center in the brain-INAH3 is less likely to be the sole gay nucleus of the brain than part of a chain of nuclei engaged in men and women's sexual behavior. I didn't show that gay men are 'born that way,' the most common mistake people make in interpreting my work. "I did not prove that homosexuality is genetic, or find a genetic cause for being gay. "It's important to stress what I didn't find," he points out with the courtly patience of someone who long ago got used to waiting for the rest of the world to catch up. It also made the unassuming LeVay one of the most misunderstood men in America. LeVay's research had provided a tantalizing clue that in the realm of sexual attraction and behavior, biology-at least to some extent-might be destiny. If that was true, being gay would be less a life-style choice, as the rhetoric of the far right would have it, than the result of a natural configuration in some people's brains. If you could spot a difference between gay and straight men in a key sexual center of the brain, that would imply sexual orientation was influenced by-or at least reflected in-anatomy. Yet small as the difference was, it suggested an enormous idea. The gay men's cell clusters were in the same size range as women's.
You could almost hear millions of nervous guys breathe a sigh of relief: yes, on average, INAH3 is bigger in straight men than in gay men (though at its most virile, the tiny nucleus wouldn't even fill the "o" in macho). Two and a half years ago LeVay, then a neurobiologist at the Salk Institute in La Jolla, California, caused a sensation by reporting a minute but measurable difference in this brain area between homosexual and heterosexual men. "There's strong evidence," notes LeVay, "that this part of the hypothalamus is deeply involved in regulating male-typical sex behavior." In his case, though, the body part in question was a speck in the brain's spongy underbelly-to be precise, a tiny cell cluster known as the third interstitial nucleus of the anterior hypothalamus, or INAH3. You might say that Simon LeVay rose to fame though a venerable locker-room tradition: sizing up the sexual anatomy of males.