First photographs of humpback sex was gay sex.

By Darwinism, homosexual behavior makes sense. Competition for resources (both reproductive access and food) leads to aggression, but a species where all the males kill each other will lack biodiversity. Physically weak male cuttlefish will camouflage as female to allow stronger get males to release on them, and then go take a female after. Things like this don’t happen unless they are beneficial. Bisexuality just makes sense, animals don’t give a shit about religions or morals and sex feeling good is going to be heavily selected for in most sexual species (notable exceptions being feline and ducks - the penis like thing that comes out of a cloaca is fucked up.)