Born gay?

The gist of LeVay's paper was this: He obtained tissue samples from the brains of 41 corpses in Los Angeles and New York. 19 of the corpses were classified as homosexual men, 16 as heterosexual men, and 6 as heterosexual women. LeVay found that a certain section of the brain known as "the third interstitial nucleus of the anterior hypothalamus", or INAH3 for short, was about twice as large in the heterosexual men as in the homosexual men, and about the same size in the homosexual men as in the heterosexual women. Therefore, he concluded, a smaller INAH3 causes a man to become a homosexual.

The media reported this study as proving that homosexuality has a biological and genetic basis, that is, that some people are simply "born gay" and it is not a matter of personal choice. Therefore, it is unfair to discriminate against or criticize homosexuals, because they didn't choose to be this way, and it is perfectly natural.

All of which has so much wrong with it that I barely know where to begin.

Side note: Mr LeVay is openly homosexual. This doesn't mean that we should simply dismiss anything he says as "biased", of course, but it is fair to listen with some extra caution, as he has an obvious vested interest. Of course, the same could be said about me: I freely admit to being a conservative Christian and the Bible has some things to say about homosexuality, plus one of my best friends in college was a homosexual who eventually died of AIDS, so I'm coming to the table with some preconceptions myself. Especially on emotional and controversial subjects like this, the wise reader will examine the arguments of all sides carefully. But anyway ...

Let's start with the technical objections: There are some highly questionable things about the way this study was done, such as:

1. Mr LeVay's sample size was far too small to be meaningful for a serious biological study. His findings could simply be the normal random variation that you always expect to find among small groups of people. This point is especially telling given that, as LeVay admits, he did not find that all the homosexuals had smaller INAH3's than all the heterosexuals. Rather, the numbers for both groups overlapped: it was simply the average that was higher for the heterosexuals.

   Mr LeVay studied other parts of the brain as well, and found no statistically significant differences. For example, he says that he expected INAH2 to also show differences, but it did not.

   Pick a group of 40 or so friends or co-workers. Divide them into groups based on something that is unlikely to have a physical basis. Say, Catholics, Protestants, Jews, whatever other religions may be represented. Then observe hair and eye color, measure height and shoe size, find month of birth, and in general take all the statistics and measurements you can think of. It is quite likely that, with such a small group, sooner or later you will come up with some measurement, purely by chance, that turns out to be different for the Protestants than for the Catholics. All this proves is that if you take enough measurements on a small enough sample, sooner or later you'll find one that fits any desired "theory".

2. Mr LeVay never explained in his paper how he determined the sexual orientation of the dead people. Presumably the dead people were not able to tell him. In his paper he refers to the heterosexual males and females as "presumed heterosexual", which rather implies that he was just guessing.

3. All of the homosexuals in this study died of AIDS. This naturally brings up the question: Is a smaller INAH3 associated with homosexuality in general? Or is it a symptom of AIDS? Countering this line of argument, six of the heterosexual men also died of AIDS, and Mr LeVay reports that the size of INAH3 in the heterosexual AIDS victims was not significantly different from that in the heterosexual non-AIDS victims. Of course now we're down to sample sizes of ten and six.

4. Mr LeVay simply assumes that a small INAH3 causes a man to be a homosexual. But surely it is equally plausible that the reverse is true: that being a homosexual causes a man to have a small INAH3. Consider: Suppose we measured the size of the biceps of weight-lifters versus that of non-weight-lifters. I expect that we would find that weight lifters have bigger biceps. Would it be fair to therefore conclude that being born with big biceps causes a man to become a weight lifter? Surely not. It would be much more sensible to conclude that regular weight-lifting increases the size of the biceps. If the INAH3 section of the brain is, indeed, associated with male heterosexual activity as Mr LeVay claims, then it is not at all hard to imagine that it might grow and develop as one "exercises" it by performing male heterosexual acts.

5. But let's suppose we even grant this. For the sake of argument, let's suppose that we really are convinced that homosexuality is something that a person is born with. The moral conclusions don't follow at all!

   Suppose that someone proved that some people are just "born racists": that there is a "Klan gene", and that if someone is born with this gene, that he will inevitably grow up to be a racist. (Hey, this doesn't sound totally implausible: racism does tend to run in families.) Would it therefore follow that it is unjust to criticize racists because they can't help how they were born, and that we should accept racism as just another "alternative lifestyle"? It would surely be disappointing if we learned that some people will be racists no matter what anyone tries to do about it, that the problem of racism is virtually unsolvable. But this would not make racism right. Likewise, even if it were proven that some people are just "born gay", this would not make it right. It would just make it tragic.

Created 11 Nov 2002. Minor update 14 Apr 2003.
Contact me.