Three studies in the early 1990’s gave birth to the widespread belief that homosexuality is determined before birth by some biological (possibly genetic) factor. Although those three studies have been largely discredited, the search for the “gay gene” or, in some cases, the “gay brain,” goes on. Now another such study is in the news, reporting difference between the heterosexual and homosexual brain.

Studies like this are invariably reported as providing evidence that people are “born gay” and can’t change, when they don’t provide anything of the kind. All they show is a limited correlation between certain biological markers and homosexuality, but one of the first principles of statistics and science is that “correlation is not causation.”

I can’t critique this entire study on technical grounds, although I have read it. The sample size of 20 to 25 in each group (by sex and sexual orientation) seems fairly small, but the authors claim statistical significance for their findings. However, they give no explanation of how the study subjects were recruited, so there’s no way to evaluate whether this sample is likely to be representative of the larger population.

What many people don’t understand is that conservatives on the issue of homosexuality have never denied that there may be biological factors which correlate with homosexuality, or even ones which may, to some extent, influence its development. But what has never been found is any such factor that can be proven to cause homosexuality in a deterministic way.

If there were a genetic or biological factor which could fix and determine for all time that a person would be homosexual, then you would expect that factor to be present in every homosexual and in no heterosexual. That’s not what you find in this study, or in any of the similar studies. While there may be a difference is the average level of “cerebral asymmetry,” for example, there’s also considerable overlap between members of the homosexual and heterosexual sample.

One irony in this study is that, in essence, all it is saying is that the brains of homosexual men are more “feminine” that those of heterosexual men, and the brains of homosexual women are more “masculine” than those of heterosexual women. But don’t homosexual activists object to that as stereotyping? I thought they liked to claim that sexual orientation and gender identity are two completely different things.

The real bottom line here is that the “gay brain” and “gay gene” studies have so far produced findings that are only marginally interesting from a scientific perspective. The real reason these studies get so much media attention is because proving that people are born homosexual and cannot change would serve the political purpose of persuading people that sexual orientation is like race, and that it should be treated like race under the law. That’s all that’s really going on in the brains of homosexual activists.

(To learn more, order Getting It Straight: What the Research Shows about Homosexuality)