Where's my ten-foot pole?

Sammler,
So you *would* touch it with a ten-foot pole? Brave man!

More seriously, here's my take on the issue:
Owen Courreges used to pretty commonly link to a study of identical twins. Among identical twins, somewhere around half of identical twins with a homosexual twin were homosexuals themselves. I think that demonstrates two things: First, genes are clearly a factor. Second, unless the other 48% are in the closet (unlikely), genes are not the only factor.

So people aren't born homosexuals, but there is obviously some biological predisposition involved (or else the rate of homosexuality between identical twins and fraternal twins would be about the same, instead of the latter being about half the former). It's possible that there is some sort of switch that gets flipped due to some experience or series of experiences, but only in some people. That could explain the proportionately high number of homosexuals that were apparently abused (by someone of the same gender) in their younger years. But that, like genes, would only be a piece of the puzzle (otherwise everyone abused would become homosexual and there would be more gays than lesbians, rather than vice-versa).

I part ways with the left on the issue because I don't see discrimination against homosexuals as the moral equivalent as discrimination against minorities. But I also part ways with the right because I don't believe it's simply a matter of waking up one day and choosing to be gay nor do I believe that homosexuality in itself is particularly damaging to society. As such, I generally agree with liberals on the subject.

There are many things in life that you aren't born with, yet are not a conscious choice either. Take taste in foods. Over the course of your life, your taste may change where at one point you hate the taste of something and at another you love it. Or take hair, for example. Bald men are not born bald. Obviously, they have the gene to product hair, but obviously something else changed the way their body functions to stop producing hair. Do these men choose to stop being able to grow hair? No, it just happens.

The main problem I see with the argument that homosexuality is genetic is that, assuming natural selection happens, then surely hundreds of thousands of years of evolution would have gotten rid of a homosexual gene. Nothing is as harmful to the prospect of procreation as not being sexually attracted to members of the opposite sex. If you're a man, and women don't turn you on, you're probably not going to have sex with them, thus making it extremely unlikely that you will pass your DNA on to your offspring. Obviously, society pressures many homosexuals into heterosexual relationships, but, evolutionally-speaking, this is probably a recent phenomenon (say the past 5,000 years). I doubt that our pre-historic man had developed to the point where social mores mandated that he couple with pre-historic woman.

As far as the study of twins that RAW discusses, it seems possible that both were brought up in similar environments and "conditioned" toward homosexuality. Unless, of course, they were separated at birth, in which case 48% would be statistically significant.

I do not believe that homosexuality is a choice, at least not for most people. I've heard that most women are 3 margaritas away from a lesbian encounter, and I think there may be something to that. Conversely, most men are NOT 3 beers away from getting down with another dude, so gender plays a factor. I could not imagine a male athlete ever choosing to be gay, not because he would be ostracized, but because men just don't do that.

Of course, I do not condone hatred toward homosexuals in any way, shape, or form. I do agree with RAW that the discrimination against homosexuals is different from discrimination against racial minorities.

If it were simply a matter of upbringing, the numbers would be roughly the same for fraternal twins as they are for identical twins or at least in the same ballpark. Instead the number for fraternal twins is less than half. (52%/22% in one, 48%/16% in the other). It's possible that a percentage with a homosexual identical twin will assume that they might be, too, but I just don't think that accounts for the entire difference. There's something genetic going on here, though it isn't determinative. I don't think a study of separated twins is necessary.

There is one study called the Minnesota Twin Project that looked at identical twins separated at birth. Of the six homosexuals they found in the group, one pair was concordant (both gay), two pairs mixed (one gay and one functionally bisexual), and three discordant (one gay and one straight). It's hard to read too much into a study of six, but three of six participated in behavior that most people don't. Two of those three pairs were men, where homosexual experimentation is less common.

It's worth noting that there is a difference between something being genetic and something being hereditary. Down's Syndrome, for instance, is the former but (mostly) not the latter. It may escape evolution that way. Or maybe there are factors in evolution that we don't know about.