This is a nice, short summary of some of the explanations for the evolution of homosexuality. It could be shorter; there are really just two classes of explanation, the adaptationist strategy of trying to find a necessary enhancement to fitness, and the correct strategy of recognizing that not all attributes of an individual organism are going to be optimal for that individual’s reproduction, so don’t even try. Love isn’t hardwired by biology, and it can go in all kinds of different directions.
So I’m saying the best answer in the list is #5. I wouldn’t be biased by the fact that the author is quoting me, no, not at all.