Are Homosexuals Born, or Made?

I agree that there is little heroic about coming out as gay in today’s society, but I did find this aspect of the Jason Collins story fascinating:

He’s my twin, eight minutes older. We live only a few miles apart on the west side of L.A. But while most of our conversations are quick and light, this one was different.

…This announcement will be surprising to some people. I already anticipate the questions: “Are you the gay twin or the straight one?” This is uncharted territory, and no one can predict how it will play out. It’s a big deal — but it’s also not a big deal. When the media crush is over, Jason will have the strength to deal with whatever challenges come from being openly gay.

One of the more contentious intersections of science and society is the question of whether homosexuals are born, or made. Both gay people and those who think them sinners have a political stake in the answer, and one of the most compelling arguments in favor of gay marriage has been that if you don’t have a “choice” to be attracted to the opposite sex, then it’s unfair to not be allowed the benefits of matrimony. Those who condemn homosexual behavior, whether out of simple disgust or for religious reasons, have to believe that gay people, indeed, do have a choice, and are simply being willfully immoral.

Now it happens that I personally believe that gays are born that way, because I am absolutely certain that I was born straight. No one ever taught me to be repelled by the thought of having sexual relations with another man, or schooled me in the obvious appeal of the female form in all its aspects, but that’s how I roll and always have ever since I’ve had any sexual awareness whatsoever. I can imagine no form of therapy (at least not involving hormonal treatments or other chemical interventions) that would somehow persuade me to change my heterosexual ways, and I would imagine that homosexuals feel just as constrained by their innate nature.

For those who, like me, accept that gay people are born, not made, there have been a number of theories over the years how it occurs. Some think it’s genetic, while others think that it may have something to do with the prenatal environment. But here we have two people who share the same genetic code, and shared the same womb at the same time, one (now) reportedly gay and the other reportedly straight, which would seem to be a problem for both theories. Interestingly (and I only learned this while researching this piece) this is not a new problem. It turns out, at least if this study is to be believed, that if one identical twin is homosexual, it’s a flip of the coin that the other one will be, whereas it’s about one in five for fraternal twins (that is, same womb, but different DNA). This would seem to be at least some evidence for the genetic theory, but certainly not dispositive.