You might say that Simon LeVay rose to fame though a venerable locker-room tradition: sizing up the sexual anatomy of males. 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. "There's strong evidence," notes LeVay, "that this part of the hypothalamus is deeply involved in regulating male-typical sex behavior."
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. 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). The gay men's cell clusters were in the same size range as women's.
Yet small as the difference was, it suggested an enormous idea. 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. 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. 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.
It also made the unassuming LeVay one of the most misunderstood men in America. "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. "I did not prove that homosexuality is genetic, or find a genetic cause for being gay. I didn't show that gay men are 'born that way,' the most common mistake people make in interpreting my work. 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. My work is just a hint in that direction--a spur, I hope, to future work."
Decades of scientific rigor have made caution a habit with LeVay. "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. 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. 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. 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. But there's no technology right now to image structures as small as INAH3."
