I definitely don't think homosexuality is a choice, however, it is equally absurd to think it is caused by a gene, because I'm pretty sure a "gay" gene would die out rather quickly.
I have no idea whether there is a gay gene or not, but the concept is hardly absurd. There are any number of genes for which having one copy is beneficial while having two has a baneful effect. For example, if one takes the stereotypes of being gay as being correlated with greater creativity, compassion, etc. as true, then gays would improve the chances that their non-gay siblings (who would have a 2 in 3 chance of carrying a recessive gay gene if there be such a thing) are able to have offspring who reproduce successfully.
So in other words, gays could be like worker ants and bees. They wouldn't have descendents of their own, but help their close relatives to have them.
