How can gayness have a genetic basis?

[All-In Flynn]

I really hope no gay posters take offence at any of the ideas kicked around below. If you are offended, please accept at least that the offence is unintentional, and don't read too much into any one of them.

I find it difficult to accept that sexuality has a genetic basis, but I see that a lot of people seem to accept it. Has this been established firmly? I remember that experimenters bred fruit flies which appeared to exhibit homosexual behaviour, but I'm not sure that this is definitive. Can someone who does think it's genetic explain why they think this?

The problems as I see them with the genetic theory go like this: If it is genetic, it is 'genome-ubiquitous' (everywhere you go, every culture has at least a knowledge of the concept). To me this implies the gene (or geneplex) is very old - older than the gene for blue eyes, say.

Nothing too controversial so far, I don't think. But then we come to the idea of reproductive fitness. At first glance, homosexuality would appear to be a very definite barrier to successful reproduction. Admittedly, gay people can reproduce, and historically they often have, but this can be argued as a function of the stigma historically attached to gayness and the oppression it has frequently encountered.

It seems pretty clear to me that gayness, while not rendering reproduction impossible, very definitely makes it somewhat less likely. And given the assumption that the gene is very old, does it not seem that less and less 'unfitness' is required for the gene to go extinct? Think of the gene's frequency as 'bankroll', generations as spins of a roulette wheel, and the 'unfitness' of the gene as the 'house edge'... it may take a while, but even the largest bankroll will eventually go broke. And even this is ignoring the difficulty of the gene spreading in the first place... if we presuppose genetic variety, where is the selective pressure to favour gayness? What kind of 'mixed strategy' could incorporate gayness as part of a successful genetic dynasty? I'm unfamiliar with any model save the 'sneaky male' hypothesis outlined briefly by Dawkins, and I'm unconvinced. Does anyone know of a better model?

I'm not satisfied with the argument that says that since gayness is alive and well, it must de facto be evolutionarily fit - this may be so if the genetic basis can be (or is) proven, but as oultined above I can't for the life of me see how.

We can, I think, dismiss recurrent mutation - current estimates vary from 5 - 15% of the population, usually hovering around ten - far too high a frequency, it would surely be unique among such mutations. And yet I've read studies correlating left-handedness with gayness; apparently one is 'ten times more likely' to be gay if left-handed, whatever exactly that figure may mean. Which of course strongly implies that there is a genetic basis...

Could it be a genetic aberration that ironically has survived precisely because of the stigma historically attached to it? (Gays disguising their gayness and thus passing on their gay genes.) Amusing to think that if Falwell and similar monsters really wanted rid of gayness, maybe they should embrace it and hope that it dies out!

The best model I could come up with for gayness having an evolutionary niche was a bit of a Goldberg, involving separate genes for male and female gayness, finding evolutionarily fit phenotypic expression in opposite genders - the gene for male gayness increasing some facet of fitness or other in women, and vice versa for the female gayness gene. The best excuse for this model I could find was the popularly-repeated notion that women are more given to gay behaviour (without necessarily being exclusive lesbians) than males... this I attributed to women lacking a Y chromosome, thus leading the 'lesbic' gene to find 'gay expression' somewhat more frequently than its male counterpart. And I have read of a theory involving genes increasing female fertility to foster gayness in men - but this I'm suspicious of. It seems to just swap the phenotypes across genders, and hey - girly-men! One thing gay men appear to be unanimous on is that they are not 'women with penises' - they are a breed apart. And while this is not strictly evidence against such a theory, I'm uncomfortable with such 'neatness' - the answer feels simple in a way that experience has led me to regard with suspicion.

So basically, after all this thinking and armchair theorising, I can't find a way to see how gayness could be evolutionarily fit, and hence can't quite accept its genetic basis - can anyone offer further insight?