Evolution and Homosexuality: Does one prove the fallacy of the other?

Over at Big Cat Chronicles, Roaring Tiger takes on LaShawn Barber's obvious gay baiting post on abortion and Homosexuality. This got me to thinking about something that has been percolating in my head for a while. Before I begin, I want to say that I firmly believe that evolution is real, and is the source of all life on this planet. Secondly I firmly believe that homosexuality is not a choice but is the result of a heretofore unknown confluence of one or more genetic, developmental, or both, influences. I firmly believe that RT did not choose to be a lesbian any more than she chose to be female. She is what she is and is happy with that. I have no problem with that, if only all of us were as happy with ourselves. These two views however have been argued by others to be mutually incompatible. If homosexuality were genetic, and homosexuality tends to limit the number of offspring, who in turn would tend to be homosexual, then those who believe homosexuality to be a choice (and further, tend to believe evolution to be a lie as well) argue that evolution would have over the centuries removed those traits from the gene pool. At first blush, this would seem to be a logical thesis. I however have to ask: What if there is an evolutionary benefit conferred by homosexuality? Or more precisely, what if the same traits (be they genetic or developmental) that can give rise to homosexuality confers some benefit to the species and it is only when other factors intervene that homosexuality results?
Let me give you an example to explain what I mean.

Northern European people tend to be light skinned, blue eyed and blonde. These all result from a lower level of melanin created in thier bodies. In the northern climes where these traits originated, the much shorter daylight length gave those who could see in low light an advantage over those who could not. Blue eyes confer an advantage over darker colored eyes in this regard. Additionally since there was less sunlight and it was colder leading to more clothing being worn, these people did not need melanin to protect them from sunlight. These two influences lead to the physiotype we see today. The DNA sequence that gives rise to blonde hair and blue eyes however, when damaged by UV light is usually mis-repaired by the body's repair mechanisms and it leads to melanoma. This is why light skinned people get skin cancer more often than darker skinned people do. So does that mean that all Blonde and blue eyed people will die of skin cancer? Of course not. And even if that were true, by the time melanoma killed them they would have likely as not lived long enough to have kids, passing those genetic traits along to thier progeny. Evolution would basically be done with them.

Now, with that concept in mind, let us return to Homosexuality. There is a branch of biology called evolutionary biology in which researchers try to approach the issue of development backwards. They look for what benefits a given gene might confer to a species and then tries to answer "what went wrong?" in an effort to understand the original purpose of a genetic trait that may be causing other problems, such as the melanoma example above, or the sickle cell gene (it confers resistance to malaria BTW).

I have to conclude that had there not been evolutionary pressure for this trait to continue to exist, it would have been wiped out thousands of years ago. Therefore I think the evolutionary biology approach might help to answer the question of why. What advantage does being emotionally attached (not sexually so much as emotionally)to members of the same sex confer? Not in todays society which is evolutionally speaking far too new to have made much of an impact as yet, but in the hunter gatherer society that humans existed in for millions of years before the advent of technology. Perhaps as a team building trait amoungst male dominated hunting parties? Or to help maintain societal order amoung female dominated encampments? Is it even more primitive? Does it arise from pack hunting societies of predators like wolves and primates where an "alpha" male and female control the rest of the group? Or is it an even more primative genetic holdover from the ability that some fish and amphibians have to change thier own sex based on environmental factors? I obviously do not have the answer, but I do believe that if we start from that perspective, we may find ourselves with a much better underlying understanding of what homosexuality really is and it's genetic and developmental underpinnings.