I had to vote no because there's plenty of evidence this isn't a recent phenomenon. However, when it comes to sexual identity that has nothing to do with the core impetus of sexual behavior, which is copulation. Evolution doesn't care who we screw when we're bored, I suspect....but it does care about making sure that we get pregnant and keep the population moving, so I would imagine and expect that there are extra motives to give impetus to insuring survival of the species. It is entirely possible that homosexuality (which tends to appear in about 7-11% of any given population, fairly consistently) likely does reflect some specific developmental advantage, either socially or biologically, though precisely what that is I couldn't say. There's a tendency among brothers in a family to have a statistically likelier chance of homosexuality in each successive sibling, for example. Is it possible that this is a desirable trait to insure that there is less aggressive competition in mating circles? We humans, of course, over-complicate everything by having lost most of our instinctive behavior, and adding in our own complex social organization and behavior into the mix.
http://www.guardian.co.uk/world/2008/dec/01/homosexuality-genetics-usa
http://www.guardian.co.uk/world/2008/dec/01/homosexuality-genetics-usa