Homosexuality, heterosexuality,  for that matter, is not from birth, nor is a learned behavior, it is the result of boredom.  It is what we do when we are not working, drinking, eating, sleeping or shitting.  If we are not entertaining ourselves there's not much else necessary.  With billions to our number, one way or another, this percentage of interactions and possibilities to a coin, we rate high.  Lol.