© HH5800/ISTOCKPHOTO.COMOur recent (not yet published) genetic linkage study of male sexual orientation predictably garnered considerable media buzz when I summarized the results during this year’s AAAS meeting in Chicago. Scientific findings concerning the causes of sexual orientation provoke intense public interest. One reason is that the topic is intrinsically interesting. Show me someone who denies interest in what makes some people gay and others straight, and I’ll show you someone who is remarkably incurious. Another reason is the widespread belief that such findings have important consequences for how homosexual people should be treated. In the U.S., pro- and anti-gay activists have long argued over the causes of sexual orientation. The belief that the causes of sexual orientation have important social consequences is wrong, however, and its persistence is bad for both science and human rights.

Pro-gay liberals tend to emphasize innate causes, and anti-gay conservatives “choice” and...

A more sensible framing is whether sexual orientation is innate or socially acquired, or somewhere in between. Innate is a more general term than genetic, and sexual orientation appears to be far more innate than it is genetic. This is because the best twin studies of sexual orientation show unusually small concordance values for both monozygotic (MZ) and dizygotic (DZ) twins, compared with those for many other human traits. To be sure, twin studies support the likelihood that genes influence sexual orientation in both sexes, but that influence appears modest.

It is still worth searching for genes—if we can find them, we can learn a lot. We can also avoid the mistake of assuming that modest heritability of sexual orientation means that it is mostly due to social influences. It isn’t—at least, male sexual orientation isn’t. We know this because of a few important cases of boys changed into girls shortly after birth, due to medical accidents or rare birth defects. Later in life these males are attracted to females, consistent with their prenatal biology but not their postnatal rearing.

I love conducting research on sexual orientation, but I do not study it because it has any implications for how we should feel about homosexual people. Our attitudes about human characteristics should (and generally do) reflect consequences of those characteristics rather than their causes. If homosexual people caused great societal damage, the way that psychopathic people do, we would disvalue homosexuality, whether homosexuality were innate (like psychopathy appears largely to be) or learned. But they don’t, and we shouldn’t. I can’t imagine a plausible scientific result about the origins of sexual orientation that would justify prejudice against homosexual people. Conversely, data about the roots of sexual orientation should not enter, much less end, a debate that inherently belongs in the moral, not the scientific, realm.

Although liberals tend to like findings that sexual orientation is genetically influenced for the mistaken reasons I’ve noted, some fear that genetic research will lead to attempts to manipulate sexual orientation prenatally. I don’t think this will happen—the likely genetic effects are too small to be useful, even if one thought this was an acceptable goal.

But no one can see the future, and it is not inconceivable that research on sexual orientation will lead to knowledge about how to change it. I oppose any attempt to limit scientific inquiry due to the fear that this might happen. In the unlikely event that techniques are developed to influence unborn children’s sexual orientation, parents should have that right, assuming they aren’t harming anyone. Shaping children is an essential goal of parenthood, and in a democracy, we have to let parents pursue some goals even if we don’t share them. Changing a baby’s future sexual orientation isn’t harming the baby. (Worries about selective abortion are worries about abortion, a debate I don’t want to enter here.) The bioethicist Tim Murphy—who happens to be gay—agrees with me.

Sexual-orientation research is irrelevant to the rights of homosexual people, who deserve equal rights regardless of what those studies show. What, then, is the point of conducting them? Sexual orientation is a fundamental human difference, analogous to differences in personality, intelligence, attitudes, and interests, most of which have been studied with considerably less controversy. Understanding how and why people vary in these traits is important to understanding human nature. The belief that sexual-orientation science has clear social implications has led to politicization of this research, however. For example, I know several scientists who were asked by sympathetic administrators to change the titles of their research grants, to hide their intention to study sexual orientation from those who would oppose funding them for political reasons. This practice reflects outrageous politicization of legitimate scientific inquiry and should be unnecessary.

The mistaken belief that data supporting inborn causes of sexual orientation justify tolerance of homosexual people leads to the equally mistaken belief that tolerance of homosexual people requires such data. Recently, the government of Uganda claimed that there is insufficient evidence that homosexuality is innate, before criminalizing it severely. We are a long way from an adequate scientific theory of the causes and development of sexual orientation. There is no good reason why homosexual people should wait for us scientists before they can obtain their human rights. 

Michael Bailey is a professor of psychology who studies the genetic roots of sexual orientation at Northwestern University.

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