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Question:
I have a question regarding biological differences between homosexuals and heterosexuals. I read your column concerning sexual orientation and the causes of homosexuality. While you did acknowledge the fact that there probably are biological differences between homosexual and heteosexual men, you didn't go any further than that. I've recently read that researches conducted on the brains of homosexual and heterosexual males (post mortem) have revealed that there are distinct differences in several areas of the hippocampus between homosexual and heterosexual males. In fact, the results indicated that certain areas of of male homosexuals' brain are very similar in shape and structure to the corresponding areas in the brains of women. This similarity to women's brains, suggested the researchers, could explain homosexual men's attraction to other men and even explain homosexuals' effeminate behavioural patterns. Opponents of this research claimed that this post mortem study is not valid, because the majority of the homosexual subjects had died of aids, which is known to wreak havoc on the brain, and which could serve as an alternative explanation to the findings.
My question is: what is your opinion of this? Which argument is the more reliable? To what extent does this reseach extend and strengthen the claim that homosexuality is genetic?
Thank you.
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Answer:
by Blaise Parker: (06/25/2004)
Hi,
You have done a good job in summing up the arguments for and against that particular study. The study that you mention is LeVay's 1991 research on the third interstitial nucleus of the anterior hypothalamus (INAH3). He did indeed find that the size of the INAH3 differed between "gay" men and "straight" men, and that the INAH3 of the gay men was 2-3 times smaller than the heterosexual men, and that it was the same size as the heterosexual women.
A number of criticisms have been leveled at this research. First, there is the one that you mentioned. Many of the subjects died of AIDS which has definite effects on the brain. Additionally, there is no good way to get a detailed sexual history. It has been argued that he included bisexual men in his study too, which may or may not confound the results. A third criticism is that the sample size was quite small. And the fourth major criticism of this research is that we cannot necessarily know the direction of cause-and-effect. Although the smaller INAH3 correlates with the assumed sexual orientation (that is, gay=smaller and straight=bigger), the brain remains somewhat plastic over the course of the life. It is not implausible to think that sexual feelings and behaviors could actually change the shape of the brain, instead of vice versa.
LeVay himself acknowledges these criticisms in an article on his homepage. He also presents a good summary of other biological evidence for same-sex orientation.
So, if you would like to know my opinion, I do think there are methodological flaws in LeVay's research, but that does not mean that I would dismiss the study as unimportant. It is one piece in a much larger puzzle, and the evidence does seem to point more and more to a biological explanation for homosexuality.
The caveats that I would offer here are the following: First, to my knowledge, no one has been able to offer a reasonable biological explanation for the existence of bisexuality, because we tend to focus on homosexuality and it's causes without worrying about bisexual individuals. I think that research on biological causes of bisexuality (if we can find any) would be very illuminating.
Additionally, I would argue that the notions of "homosexuality" and "heterosexuality" have been created through our own use of language and labeling. The labels for homosexuality and heterosexuality appeared around Victorian times, and before that there doesn't seem to have been a notion of what it means to "be gay" or to have a "gay identity". Therefore, I would not completely rule out the effects of culture on sexual orientation, at least as far as people understand their own identities.
There are other cultures that have same-sex sexual activity (both across the world now and throughout history) that have had same-sex sexual behavior without discussing what it means or what causes it or whether it is right or wrong. This to me is evidence that we have at least somewhat created the current debate around and meaning behind sexual orientation.
If I am being unclear, let me give this example. We know that height is both genetic in nature (how tall the parents were, for example) and influenced by environment (nutrition, for instance). We can say that without being politically controversial because we haven't created a great deal of loaded meaning behind "short" and "tall". There is no talk of a short or tall identity, or whether it is wrong or right to be short or tall. Mostly (except in extreme cases) people just shrug their shoulders and go on with life.
That's what I think sexual orientation is. It's probably something of both. It's nature, it's nurture. But it has meaning (which is really the crux of the matter, no? why would we care about finding a "cause" if it didn't matter much?) because we ascribe it meaning.
That was probably more than you needed me to say, but there you have it. That's my take on the matter. :)
Take care,
BlaiseReviewed by Sexual Health Editorial Team
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