"Gay, Straight, and the Reason Why": Where does homosexuality come from?

Does birth order affect sexual preference? Why are some animals bisexual? A new book probes a heated topic

Published October 24, 2010 7:01PM (EDT)

What makes a person gay? Is it genetics, upbringing, or some combination of the two? Over the past few decades, a slew of scientific research has bolstered the notion that sexuality is, at least in part, innate. Studies of the sexual behavior of various animal species have shown that homosexuality is not just a human phenomenon. Then there is the curious finding that the number of older brothers a male has may biologically increase his chances of being gay.

Now Simon LeVay, a former Harvard neuroscientist, has written, "Gay, Straight, and the Reason Why: The Science of Sexual Orientation," a comprehensive, engaging and occasionally quite funny look at the current state of the research on the topic. LeVay is one of the leading authorities in the field: Back in 1991, he discovered that INAH3, a structure in the hypothalamus of the brain that helps to regulate sexual behavior, tended to be smaller in gay men than in straight men. It was a watershed moment in our understanding of sexual orientation (the study was published at the height of the AIDS epidemic, when the disease was widely regarded in religious circles as divine punishment for the sin of being gay) and the first scientific finding to support the idea that gayness might be more than just a lifestyle.

Salon spoke with LeVay over the phone from his home in West Hollywood about sexuality and the developing brain, gay sheep, and how science can help prevent anti-gay bullying.

Why do you think this debate is so important?

The fact is, a lot of anti-gay attitudes have been tied to the notion that homosexuality is a lifestyle choice. The biology tends to run against that, plus it's just absurd, because if it were a choice, people would remember making it -- and they don't. When people are talking about a lifestyle choice, well, of course it is a choice in the sense that people choose to make what they want out of these feelings of sexual attraction that they have. There are plenty of gay people who've gotten heterosexually married and had kids. Even Oscar Wilde did that. There are also plenty of straight people who engage in gay sex under certain circumstances.

But I don't think anyone chooses to experience the underlying attractions. At that level, I think the biology really argues against the point of view that the Christian right has presented, of homosexuality as being nothing more than straight people saying to themselves, "Oh, I think I'll try that gay thing this weekend." That's the sort of level that they sometimes want to reduce us to.

You devote a section of the book to sexual orientation in other species. Why is that important to our understanding of it on a human level?

The most famous example are these so-called gay sheep. There was a group of sheep breeders in Idaho who couldn't breed some of their prize rams. They put them together with the females and they just wouldn't perform. So they took the rams to an animal psychologist who studied them for about a year and said, "Look, you've got gay sheep here." It seems that about 5 percent of rams have that preference.

Chuck Roselli and his colleagues at Oregon Health Sciences University looked at their brains and found something very similar to what I found in my study. The structure in this part of the hypothalamus, which actually has a different name in sheep, is also smaller in these male-oriented homosexual sheep than in the female-oriented sheep. That was a confirmation of my work in the sense that it got away from the whole disease angle. I had to collect brain samples from gay and straight men, and at that time most of the gay men had died of AIDS. So some people thought it was a disease that was affecting this part of the brain, rather than sexual orientation. The fact that these sheep were completely healthy gets very much away from that kind of interpretation.

Does naturally occurring homosexuality happen elsewhere in the animal world, in the wild?

Much more common are animals that are to some degree bisexual. They will, on some occasions, mate with same sex partners and, on other occasions, other-sex partners. For example, in bonobos, our oversexed primate relatives, you see all kinds of sexual behavior depending on social circumstances. Animals use sex for purposes beyond reproduction: for forming alliances, swapping sex for material things like food and so forth. And you see same-sex pairing in many bird species.

In breeding colonies of seagull species where there's an excess of females, you'll have female/female mating. It's not really the case that you've got individual animals that have a predisposition to be homosexual or heterosexual. It's a tricky thing to actually find what we call "homosexuality" in the wild, because you really have to follow animals for long periods of time. They're all having sex with each other, but you've got to figure out which of them actually prefer doing that.

Yeah, and you can't exactly ask them

(Laughs) Exactly. Humans seem to be sort of unusual in that many of us are strongly predisposed to be sexually attracted to either males or females.

Why is that?

Well, we don't know, but I think the answer will emerge from the study of brain development.

You point out that even though the research is more and more support of the idea that gays and lesbians are born gays and lesbians, that they should be accepted even if it were a choice. Which I think is a really good distinction to make, because the drawback to the biological argument is that it can start to sound apologetic in a way.

Yes, it can sound apologetic, and one can also say, "Oh, what about bisexuals? Maybe they're not entitled to protection because they do have a choice." Or maybe sexual orientation is more fluid in women than in men, so, do we give more rights to men? It starts to get a little ridiculous if you really parse it out in detail.

One of the groups that I'm very popular with is PFLAG, because they have traditionally borne the "blame" for their kids being gay. So they see my biological line as getting them off the hook, in a sense. I usually say to them, well, in the 10 years or so until we all realize how cool it is to be gay, you'll be changing your tune, saying "Oh, I made my kid gay by reading him a chapter from 'Great Gays in History' every night or something like that." I really think that there are plenty of reasons why gay people should be welcomed in the world. Parents should be blessed to have gay kids.

Given that gay people don't reproduce in nearly the same numbers as straight people, how do gay genes survive?

The usual idea is that a gene predisposing some individuals to homosexuality might promote the reproductive success of others, and the two effects might balance out. It might be that a gene predisposing a man to be gay might make a woman even more attracted to men than she otherwise would be, so that she would engage in more heterosexual sex and thus become pregnant more often. There are a couple of studies reporting that women who have gay male relatives (and who may therefore carry the same "gay gene") do indeed have more children than women without any gay male relatives. The answer will remain speculative, however, until the actual genes have been identified and their mode of action worked out.

The idea that birth order affects sexual orientation in males on a biological level, and that gay men are more likely to have older brothers, is a relatively new one within this field. How do we know that it's not just a social effect?

At first I tended to think it was social, because there have been all these studies on the influence of birth order on mental traits. But that really does not seem to be the case at this point, based primarily on a study [by Tony Bogaert] looking at boys who were adopted out of their birth family. It seems to be the actual birth order of the biological family that matters, not the actual experience of growing up with or without an older brother.

The mother generates some sort of antibodies against the initial male fetus, which interact with the developing brain of later pregnancies with male fetuses, in such a way as to make that fetus more likely to be gay later on. Researchers think that this "older brother" effect accounts for up to about a quarter of the total causation of homosexuality. They are in the process of actually pinning down the biological mechanism involved, so maybe in a year or two we'll have some more direct evidence.

The concept of gender nonconformity comes up in the book a lot: that many people who are gay tend to have traits that are typically associated with the opposite sex. How is this explained in biology?

You have to be really careful, because this is definitely an area of stereotyping, calling a gay man queeny, or lesbians butch. But it does seem that there's a kernel of truth to the idea that being gay or lesbian is not an isolated trait, but part of a package of gendered traits that go together. And what I think is behind that is that during fetal life, the brain is differentiating in a more masculine direction or a more feminine direction under the influence of sex hormones circulating in the fetus's body, mostly testosterone. So it produces people who are not just different from the mainstream in terms of who they want to have sex with, but also in many other aspects. You see that, for example, in that gays and lesbians tend to be overrepresented in certain occupations. And again, you're very much near a stereotype. If people think I'm trying to say that every gay man should be a male nurse or something, and every lesbian should be a professional golfer, then no, that's completely ridiculous.

Issues of bullying and the struggles of growing up gay are kind of center stage right now, with the recent rash of suicides and things like Dan Savage's It Gets Better project. How do you think the work in this field is going to play a role in avoiding these sorts of tragedies?

First of all, yes, it's just horrible what has happened to these kids. When you see these boys and realize what a normal cross section of teenagers they are, it's pretty horrifying. But the way people think about gay people right now, in comparison with a generation ago, the differences are spectacular. Happy, out, gay kids are living like normal teenagers in a way that was not possible a short while ago.

But these kids who are gender-nonconformist at 7, 8, 9 years old, do provoke a tremendous amount of bullying. One thing that this research says is that you have to go to earlier ages and think about what the experience is like for children. The biology points us in a direction of recognizing these children as "born gay" with an entitlement to respect for that difference, just in exactly the same way that a racial group should be entitled to that kind of respect and protection.

But is that problematic in its own way, since we don't really know before puberty whether or not someone is gay or straight, and especially since people with these nonconformist gender traits often ultimately turn out straight? Is there a danger in singling them out for something they won't even realize until much later?

I think gender-nonconformist children should be protected and respected for what they are, not what they may become in the future. Most experts believe that the important thing is to support the child as he or she is. So my advice -- and I'm in no way an expert in this field -- would be for parents to accept their child's gender-nonconformity, and to point out that a grown man or woman can be anything from a ballet-dancer to a marine, and can be in relationships with men or women or both, but not to celebrate "our gay son" or whatever. Parents also do well to point out how mean people sometimes can be, and how the child can take steps to minimize the hurt.

There's a common fear that if a gay gene could be isolated, then it could be eliminated. Is that something that's feasible?

It's not feasible right now, because no gay gene has been identified. We know that genes play a role, but we don't know which genes they are. Now, if it should be found that there is a gene or a small number of genes, each of which has a major effect on sexual orientation, then yes, you could certainly imagine that at some point in the future it might be possible to, say, if you had a bunch of embryos, choose one that was predisposed to have the sexual orientation that you wanted it to have. For most people, I suspect, that would be straight.

This is not true just for sexual orientation, but for our entire makeup as human beings. A lot of this is going to eventually come down to a genetic menu that people might be able to pick and choose from, thanks to the Human Genome Project. It's a major ethical dilemma that we are going to have to face in the next decade.

By Schuyler Velasco

Schuyler Velasco is an editorial fellow at Salon.

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