One idea that came through my head was that social pressure was probably a very influential factor that sustained homosexuality. Thats to say, social pressure exerted upon homosexuals forced them to undergo the process of reproduction, and hence that anomaly was sustained through human generations. Following this line of thought, it seems that the easiest way to eliminate homosexuality is to allow guilt-free homosexual activity, since this would simply decrease the survival value of the homosexual "gene".
But again, saying that homosexuality is an anomaly might not be wise. Much evidence shows that many animals exhibit homosexual behavior. Those animals probably don't face the same kind of social pressure that humans exert.
This evidence has challenged Darwin's "sexual selection" theory [NOT "survival of the fittest"]. Darwin simply viewed sexuality to be motivated by reproduction. But strong evidence shows otherwise. The truth is, as humans, most sexual encounters are not reproduction related, and don't fit Darwin's description. Consider this:
Darwin had very specific sex roles for males and females. He wrote that females are docile and dainty and always prefer mates who are attractive and vigorous. But the world doesn't work like that. A quick look at humans tells you that women don't always prefer musclebound models. It's really obvious, but women choose all kinds of men as mates, and very rarely do those choices have to do with exhibited traits, like the peacock's tail or a stag's antlers, that Darwin thought represented "good genes."
In fact, the whole good-gene idea is suspect. The idea that a female could look at a male and tell by his appearance how good his genes are and how those genes are going to play out in 20 years is extremely far-fetched. Scientists have been trying to prove this idea experimentally, and it never bears out. It doesn't bear out, because not even supercomputers can offer that kind of predictability. (source)
In short, I think anyone who would say that homosexuality is an anomaly, or would think that homosexuality has no survival value, is shown to be incorrect by evidence from our reality. Homosexuality has gained ground in many aspects of life, including the political arena... This can't be an anomaly that we are talking about! Homosexuality should have a function in humanity that caused it to have such strong presence, and denying that is being blind to the fact of its influence...
PS: The scientific validity of the claims is NOT asserted