Originally posted by HuckFinn
How this trait is passed to future generations is beyond my comprehension... according to my model, homosexuality should die out within a generation as they would be unable to naturally reproduce.
Remember that half the genes any one person carries are masked (and totally dormant) by the dominant set of genes, whatever that sorts out to at conception. All those dormant genes have a chance of passing to offspring; and may remain dormant or may resurface. Some genes skip every other generation, or manifest only when paired with others, or otherwise play peekaboo by random or obscure cause. If there is a "homosexual gene" you can bet at least as many heterosexuals carry it dormantly. Maybe we all carry it.
Sterile worker bees don't die out. They occur and reoccur by the magic of genetics. Their existence shows how genetic variation within a cooperative extended family can benefit the family as a whole. I think humans have been around long enough as "cooperative extended families" that genetic predispositions within the clan might be useful. Maybe primitive man survived better when not all members of the tribe were "breeders". I can imagine how that might come in handy.
My personal observation is that if one has uncles or aunts, there's a very good chance one of them will not have children. This is can be very useful to the family as a whole. These unburdened adults often function as temporary caregivers to various family members, as needed. They mind your kid when you're sick, they help grandpa take a bath, they spoil the twins. Why not make it genetic?
I wouldn't call a gene which accomplishes this a "defect".