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Sex and the Brain

In the summer of 1991, neurobiologist Simon Levay published a small study on a minute part of the human brain. Little did he realize it would catapult him from his scientific ivory tower into the heated fray of homosexual politics.

By David Nimmons
Mar 1, 1994 6:00 AMNov 12, 2019 5:19 AM


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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."

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. 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. But people get nervous, as if I'm painting gay men as women in disguise."

LeVay hardly seems the sort to inspire controversy. 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. He still has the trim body of a competitive bicyclist, which he was for three decades. Dressed, as usual, in jeans and an open-necked shirt, his appearance might be described as a precarious equilibrium between natty and rumpled. You wonder what made this quiet, unthreatening academic venture into "such a touchy subject," as he calls it.

LeVay was by no means the first to find sex-related anatomical differences in the brain. Neuroanatomists have documented such sexual dimorphism in brains since the early 1980s. "The corpus callosum--the nerve bundle connecting the two brain hemispheres--is relatively larger in females," LeVay points out. "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."

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. "Laura showed that the INAH3 area in humans was, on average, more than twice as large in men as in women," explains LeVay. "Now, INAH3 is in a part of the hypothalamus known to be involved in directing typical male sex behavior, such as attraction to females. So I thought it reasonable to speculate about dimorphism by sexual orientation as well as gender." Would the difference that showed up between men and women, he wanted to know, also show up between straight and gay men?

Since the area can't be studied in the living, the work had to be done posthumously. Altogether LeVay autopsied the brains of 41 people--19 homosexual men, 16 heterosexual men, and 6 women--painstakingly dissecting, staining, and measuring their INAH3 clusters. It was no mean feat: at its largest, the human INAH3 constitutes approximately .000009 percent of the brain's mass. To avoid biasing the results, the study was done blind--that is, each brain sample was numerically coded to conceal whether its donor was straight or gay. After nine months of peering through his laboratory microscope, LeVay sat down one morning to break the first blind codes. "Once I'd decoded the first third of the sample, I saw what the data were telling me," he says, excitement edging into his usually soft voice. His hunch had apparently paid off. According to his lab notebooks, gay and straight men did differ in a key area controlling sexual behavior. The largest INAH3 clusters tended to belong to straight men, the smallest to gay men; in fact, on average, straight men had clusters twice the size of gay men's. "I was almost in a state of shock," LeVay recalls. "I took a walk by myself on the cliffs over the ocean. I sat for half an hour just thinking what this might mean."

When the study was published in August 1991, it attracted immediate attention--no doubt partly because it was reported in a journal with Science's prestige by a neuroscientist with LeVay's credentials. LeVay--raised in London, the son of a physician and a psychiatrist--has a master's degree in natural sciences from Cambridge and a doctorate in neuroanatomy from Göttingen University in Germany. In 1971 he moved to Harvard, joining the team of David Hubel and Torsten Wiesel, who won a Nobel Prize in 1981 for their work on the brain's visual system. In 1984 LeVay moved to the West Coast to head his own vision laboratory at the Salk Institute. "Until 1990 all my work was very basic, fundamental vision research," he recalls. "I studied how the brain integrates the input of our two eyes to give us a single, three-dimensional view of the world. It was a bit ivory-towerish, really."

His study on sexual orientation was something of an anomaly. Not that he hadn't thought about it in the past. "I've known I was gay since I was about 13," he says, his tanned face breaking into a grin. "As a gay man, I had the motivation to do this work. If I didn't, nobody else was in a hurry to do it. And as a scientist, I knew it was research I was qualified to do. I was already working on structure and function in one part of the brain, so working on the sexual part of the brain wasn't a big switch."

What ultimately changed the direction of his research, though, was a deeply personal crisis. In 1990 LeVay's partner, Richard, an emergency room physician, died after a four-year struggle with AIDS. "Richard and I had spent 21 years together," he recalls, his voice still catching at the memory. "It was while looking after him that I decided I wanted to do something different with my life. You realize life is short, and you have to think about what is important to you and what isn't. I had an emotional need to do something more personal, something connected with my gay identity."

With the publication of his paper, LeVay's 15 minutes of fame exploded with a vengeance. In just a week he was rocketed from the hushed halls of the Salk Institute to the glare of MacNeil/Lehrer, Oprah, and Donahue. His work, career, and life were dissected on Nightline and in Newsweek. "It was quite a shock," he recalls. "I wasn't prepared to talk about the private aspects of my life; I never had talked about them, especially about my lover, in public. I found it very off-putting."

LeVay was pelted with questions. Because his gay subjects had died of AIDS, some critics questioned whether the AIDS virus could have skewed his results. LeVay thinks that "highly unlikely." He'd also included in his study six heterosexuals who'd died of AIDS and saw no difference in INAH3 size patterns between these patients and those who had died of other causes. (Nevertheless, to assuage his curiosity, LeVay later examined the brain of an HIV-negative gay man who had died of lung cancer: "I was very, very nervous when I decoded that sample," he admits. "I'd have lost a lot of faith in my data if that case had contradicted it." Yet that brain, too, fell into the gay-typical range.)

Anne Fausto-Sterling, a developmental geneticist at Brown University and one of LeVay's chief academic critics, was among those who questioned the way he interpreted his data. "He claimed a wide variation in the size of these brain nuclei in gay and straight men," she says, "but there was still a broad overlap between straight and gay. What he actually found was a distributional difference, with a few larger-than-average nuclei at one end, a few smaller-than-average nuclei at the other, and the vast majority falling in between. Even if we could say most people at one extreme were straight, and most at the other extreme were gay, that tells us little about the majority in the middle where the ranges overlap. If LeVay picked a nucleus size in the middle, he couldn't tell if it was heterosexual or homosexual."

Fausto-Sterling also took issue with LeVay for reducing the many subtle shades of human sexuality to a gay-straight dichotomy. "There are many gradations in sexual orientation. What do you call men who have sex with their wives while fantasizing about men? Or guys who are mostly straight who pick up male prostitutes, or transsexuals, or serial bisexuals who may switch between exclusively gay and exclusively straight relationships? How do you count sexual behavior that changes over time in different circumstances?" She described LeVay's research as part of "a reification of sexualities into a binary scheme. It maps very poorly onto reality and makes thinking about the biology very tricky."

"That's a valid criticism, one I totally accept," says LeVay. "One just has to start somewhere, with simplifying assumptions." He also regrets excluding lesbians from his study. "One tragic result of the AIDS epidemic is that it's much easier to obtain brain samples of men known to be gay. Sexual orientation is far less likely to be noted on the medical charts of women who are lesbians."

The public's response to LeVay's study was equally spirited. "Some of it was loony stuff," LeVay says with a smile. "Wild theories that it's all due to diet. Then there were the letters from religious zealots, flatly stating that being gay is a sinful choice, as it says in the Bible." In the gay community some people branded LeVay a biological bigot and called his work an expression of internalized homophobia. "One critic said I wanted to prove that it's not my fault I'm gay," says LeVay, clearly pained. "I thought his charging I was a conflicted gay man was a bit off- color; I've been open about being gay since I was a teenager." LeVay also rejects another criticism: "Some say my work means gay men are simply 'straight men with a hole in their hypothalamus,' that it pathologizes gay men. I don't buy it. To say that, you'd have to consider it pathologizing to say that gay men have something femalelike, which I don't see as true. I don't think there's anything pathological about being a woman."

But the more typical response was enthusiasm. Letters poured in from gay men and their families. "Many gay men sent my study to their parents, particularly if they were somewhat estranged from them. And parents, in turn, wrote to say the study helped them understand their kids." It's obvious that LeVay takes pleasure in knowing that many people have found his labors useful.

"Some parents think of me as the person who took them off the hook," LeVay says, smiling. "They tend to see my work as proof that being gay is genetic. It's a mistake I am sympathetic with, because I happen to think gay people quite likely are born gay. Since I consider my work moving in that direction," he adds wryly, "I am not totally uncomfortable with that reaction."

In fact, LeVay has long suspected that homosexuality runs in families and has an inherited component--a suspicion reinforced by recent twin studies by psychologist Michael Bailey of Northwestern University and psychiatrist Richard Pillard of Boston University. The studies show that identical twins--who share the same genes--are about twice as likely to both be gay or lesbian as are fraternal twins, who share only half their genes. They are also five times more likely to both be gay than are adopted brothers who share an upbringing but no genes. "That clearly suggests that genetics accounts for a substantial fraction of the total causation," says LeVay. As anecdotal evidence, he shows off a family snapshot of himself and his four brothers: "Two and a half of us are gay," he says. (One brother is bisexual.) "You know, my father has never been comfortable that I'm gay. He doesn't approve. Since all the kids from his second marriage are straight, he insists it's all inherited from our mother's side of the family."

LeVay's disapproving father may yet be vindicated. Last July, LeVay points out, Dean Hamer's team at the National Institutes of Health located a region on the X chromosome of gay brothers that may turn out to carry a gay gene or genes; the X chromosome is, after all, always the mother's genetic contribution to her sons. Just how a gene in this area might make someone gay remains anyone's guess: maybe it influences how sex- related structures are formed in the hypothalamus. When it comes to sexual attraction and behavior, LeVay suspects, humans are largely shaped in utero. "Something different is happening when the gay brain organizes itself in fetal life," he says. "If I put my money anywhere, it's on the interaction of sex hormones and the brain. There may be genetic differences in how the fetus's brain cell receptors respond to sex hormones such as testosterone."

LeVay thinks that over the next five years the genetic influence on sexuality will become much clearer. And if Hamer turns out to be right, of course, the human libido would be pretty much set at the factory. Though upsetting to some, the notion jibes with accumulating evidence from biologists and ethologists that evolution has preserved diverse sexual orientations. Homosexuality has now been documented in dozens of species, from primates and elephants to sea gulls and fruit flies. But that raises a profound question: Why?

"It seems paradoxical, doesn't it?" says LeVay. "At first sight homosexuality seems not to favor reproduction, so why does it persist?" LeVay can only speculate on the phenomenon. Being gay might somehow foster the survival of one's relatives, who in turn pass along part of one's genetic heritage. But then you would expect homosexual animals to spend their time taking care of infants or getting food, and there's no real evidence that they do. Alternatively, perhaps genes linked to homosexuality confer some other benefit that's selected for, and homosexuality just persists as a by-product. "But there's an awfully big reproductive cost for homosexuality," says LeVay, "so whatever characteristic goes along with it must be highly advantageous, like, say, creativity." Another theory posits that homosexuality may be part of a selection for reduced aggression--what LeVay terms "the fights-break-out-at-football-matches-but-not-at-the-opera theory." "Frankly, none of these theories seems very satisfactory to me," says LeVay. If nature has some grand design for the homo in Homo sapiens, he admits, "it remains a mystery for now."

These days LeVay lives in a modest West Hollywood apartment that reflects an artist's life more than it does a scientist's. The walls of the small kitchen are papered with exquisitely detailed pencil and ink sketches LeVay has made of his father, his deceased lover, a pensive woman in a café. On the facing wall hangs a gay rainbow flag LeVay painted in fluorescent acrylics. A jumble of dusty cycling trophies and medals adorns the tops of the bookcases in the living room. The shelves spill over with some 1,200 books, an intellectual smorgasbord running from Montaigne to Bertrand Russell to paperbacks on vegetarian cooking.

The lone clue to LeVay's profession is a framed photograph. At first glance it could be mistaken for a lightning bolt in iridescent yellow and orange, or perhaps a river viewed from a great height. In fact it's a micrograph LeVay took of a single neuron meandering through the miasma of the visual cortex. "You've no idea how beautiful the brain is," he says. "I love looking at it through the microscope. You can choose a small patch of cells out of the millions of neuronal cells in the visual cortex, staining them yellow with a dye. And as you focus down through them, it's like going through this incredible forest of neurons. You see all the little bumps-- the synapses, where the connecting points between neurons are. If you use an electron microscope, you can even see thousands of vesicles containing the transmitters that shuttle messages across the gap between the synapses. You see it all. As you focus your way through layer after layer of cells, you feel like you're walking through a cathedral filled with tracery and filigree and delicate architecture.

"I remember once swimming in Walden Pond, floating on my back at night, looking up at all the stars. I felt I was actually floating out there in the universe. For me, looking at the brain is somewhat similar: you feel as if you're really inside it, with the same sense of spaciousness." LeVay cheerfully admits to "spending hours looking at the beauty of it all, not really looking for anything. You can explore it forever and never exhaust all the beauty and complexity that's in there."

But he is keenly aware that there is danger as well as beauty in research like his. "Historically, there has been terrible homophobia in medical research. Farcical science--like the explanation that in gay men the nerves of the penis were misrouted to the anus, transferring the erotic response there. People were given electroshock and aversion therapy to change their sexuality. It's an ugly history of scientific and medical oppression of gay people."

Does LeVay worry about his own research being misused? "If scientists find a gay gene, and I think they will, it opens the possibility--even a probability--of misuse," he answers. The dangers he foresees include discriminatory employment tests and fetal tests followed by abortions of potentially gay children. That doesn't mean the search to understand sexual orientation should be given up, argues LeVay. "You avoid misuse by helping along the process of society accepting gay people. I would be very unhappy if mothers aborted fetuses more likely to be gay, but you don't prevent that by inhibiting research, or by prohibiting testing or abortion. You do it by education, by helping people understand that it's okay to have gay kids."

Although science is the bedrock of the educational process, LeVay has become convinced that it's not enough. "Science alone can only go so far in rolling back prejudice, because prejudice is based in irrationality and can't always be approached with rational arguments. There's a human dimension to it that also needs to be addressed. Besides," he continues, "on a purely moral level, there's no justification for discrimination against homosexuality, regardless of its causation. Even if homosexuality were not biological--even if it were a conscious choice--there would still be grounds to respect gay people, because of our beliefs about people's right to privacy and freedom of action and because of the contributions gays and lesbians make to society."

That realization led LeVay to his next decision. Less than a year after his Science paper appeared, this world-class scientist did the unheard-of: he resigned his academic positions, returned a half-million- dollar research grant to the National Institutes of Health, and quit his life in the lab. By then, he admits, the lab had lost some of its allure. "At a certain stage you become an administrator, raising money to pay for research and bringing in others to do the work you'd like to do yourself," he explains. "And I realized, when I'd come to the end of my life, I wanted to feel I'd done something to give me personal satisfaction. It's not entirely rational, but a lot of gay men are propelled into activism as a result of their experiences with AIDS. Richard and I were a couple, a hardworking doctor and a scientist, but not really involved in the gay community. His illness changed that."

In the spring of 1992, LeVay left Salk to help found a very different kind of institute: the West Hollywood Institute of Gay & Lesbian Education. The idea was born on a summer's bike ride taken by LeVay and a friend, Chris Patrouch. "Most gays and lesbians miss out on learning about their own culture and history. We aren't brought up by gay families, teachers don't tell us much, there's a huge gap in our knowledge about ourselves." Over several more bike rides, LeVay and Patrouch forged the idea for an extension college for adults, taught by gay and lesbian academics on nights and weekends. With another cofounder, Lauren Jardine, they persuaded the city of West Hollywood to provide classroom space. At first glance, it seems a typically dowdy classroom, right down to the American flag at the front of the room, until a closer look reveals the remnants of a gay Spanish lesson on the blackboard. The school--which is open to all--offers courses on topics such as sexual orientation and the law, homosexuality and religion, and literary sources of contemporary gay and lesbian identity. LeVay hopes that by better knowing themselves, students will become better ambassadors for the gay and lesbian community in the world at large. (The model student of the institute may be LeVay himself. "Last semester," he says happily, "I went to a different class each night.")

Meanwhile, the notion of a biological basis for homosexuality-- the notion LeVay helped generate--has taken root in the most unlikely places. Posted on one of the institute's walls is a flier from a rural Tennessee town; it announces a "Christian fellowship breakfast for people who happen to have been born gay or lesbian in affectional orientation." In Phoenix, William Cheshire, a staunchly conservative columnist for the Arizona Republic, wrote a startling editorial in June 1992 endorsing an ordinance to protect homosexuals against discrimination. "My moral perception came out of my religious background," Cheshire later said in an interview on British television, "but when I read the scientific evidence, I became persuaded that it was not something voluntary. . . . If it is the way you were born, then it ceases to be a sin, and one's whole theological and moral perspective shifts."

Now LeVay's work is moving from the lab bench to the judicial bench. Last year, in a precedent-setting decision, the Hawaii Supreme Court ruled that denying gay couples marriage licenses appeared to violate the state constitution; in a concurring opinion one of the justices cited research that homosexuality is "biologically fated." "Research suggesting that sexual orientation is deeply rooted or even has a biological component helps courts see why gay men and lesbians should be protected from discrimination," says Evan Wolfson, an attorney in that case. In the coming year, the debate over gays in the military will probably set the work of LeVay, Hamer, Pillard, and others before the nation's Supreme Court. "As in all equal-protection cases, biological evidence will play a role," comments Kevin Cathcart, executive director of the Lambda Legal Defense Fund, the lesbian and gay legal-advocacy organization. "Biology is an element the courts have traditionally used as a marker for the immutability of a characteristic, such as race, gender, or--now--sexual orientation." The "immutability" argument is also being used to combat antigay initiatives, such as the one in Colorado that was overturned in December.

Asked what role he now sees for himself, LeVay looks amused. "I sometimes block on those little forms at the bank, where you have to state your occupation. I used to write scientist; now I put writer or teacher." Other than that, he has scarcely looked back since he closed the lab door behind him. "Sure," he says, "there are times I'd like to do some experiment. I'm interested in the work that Hamer and Cassandra Smith at Berkeley are doing on androgen-receptor gene expression. That's when I have to remind myself I don't have my lab anymore. Sometimes I feel a little like I deserted an area where there is so much to do. But I don't expect to make further contributions in neuroanatomy--others can do it. I'd rather concentrate on education."

The institute is one part of that educational effort. In addition, to help people catch up with recent work on sexual orientation, LeVay published a book last year called The Sexual Brain. He is now writing a much more ambitious book, Queer Science, a history of the study of homosexuality from Plato to the present day. (He is also writing a primer on lesbian and gay culture with lesbian novelist Elisabeth Nonas.)

LeVay believes that as a society we all stand to benefit from understanding homosexuality as part of the spectrum of human behavior. "Knowledge about ourselves as humans is the most basic knowledge we can acquire, and our sexuality is a big part of that. True, this kind of knowledge can be misused, but the only way around that problem," he insists, "is to keep expanding what we know rather than having just snippets.

"In the long run, expanding our knowledge is the only way to avoid fostering oppression. Just because there's been crazy science and wrong thinking in the past doesn't mean we should give up doing science on the subject. We should do better science. After all, isn't that the point of it all--bringing us closer to the truth?"

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