When your 400 trillion sperm are waiting around for the egg to be ready in increasingly hostile situations, some males on the outside, recognizing that copies of them are on the inside, will sacrifice themselves to create a protective barrier so that the ones on the inside can last longer, this is a kind of selective pressure for homosexuality in that is possible to procreate without having sex only through behavior that prevents the loss of life in a version of you that is expressing itself in someone who is for the most part a duplicate of you of DNA.

And so homosexuality only makes sense in tribal pack animals, and so I wouldn't be surprised to see it show up in animals in such case where many males have to work as one for one of them to survive, thus creating the selflessness actor in it's better than one die than both. And thus creates the evolutionary pressure for homosexuality to procreate when troop tribe pack animals, during famines. Horses come to mind.

It's possible to procreate your DNA using only behavior, because the simulation gives equal credit to a woman making a great copy, to a man who prevents loss of that good copy. The universe understands that -1 * -1 is positive and 1 * 1 is positive. You can add this positive and take away a negative in two ways, resource gathering and enemy wrecking.

Jesus christ get this down from 2000 characters to 200.