There is an enormous amount of research that supports this notion.
http://en.wikipedia.org/wiki/Prenatal_hormones_and_sexual_orientation#Prenatal_maternal_stress
I think people get carried away too much with Dawkin's Selfish Gene notions of survival of the fittest.
Like most of the rest of the 1500+ animals that are known to exhibit homosexual behavior, Humans are social animals. Thus it is actually about survival of the fittest society.
Also, Nature really hates to re-invent the wheel and sex is simply way too good of a behavioral reward system to limit it to procreation.
The next time a straight person tries to tell you that homosexuality is an obvious birth defect or learned deviant behavior then ask them if they feel the same way about a straight female being sexually receptive when she is not in estrus????
Humans are naked, sweaty, bipedal apes because the males were designed to chase furry prey under the African sun until they have a heat stroke. Modern African tribal hunters, that still live this life, often have to chase a prey animal something like TWENTY MILES.
Whereas at the same time, human big headed infants are completely helpless for months and the mother & child need the male to provide for them.
So what gets the guy to want to drag back the kill 20 miles instead of sitting down and having a big lunch?
Oh yeah, having sex pops in his head every 20 minutes.
One of the most cited studies regarding the prenatal origins of male homosexuality relates to the pregnant mother enduring stress.
So what could cause her so much stress that she would find a solution (that gains evolution's favor) while at the same time being partially contrary to her own genetic legacy?
Oh yeah, too many Macho males threatening the survival of the community by fighting constantly.
If you look a Bonobo chimps with their anything-anytime-anywhere-and-with-anyone-including-the-young-children approach to sex, you see they sue it as a social glue to solicit food gifts and to reduce stress among other reasons besides making monkeys.
Also the taboo of pedophilia is a western social construct and not a human instinct (as a survey of other cultures will reveal). Too, in these other cultures the adults don't feel or behave like perps and the children are not made to feel like victims, and thus, thay suffer no psychological harm.