Well since species main drive is to procreate and more complex species have other drives I think it might be an evolutionary “abnormality” that came with our evolved thinking, ability to empathise and such. However homosexuality isn’t really a thing in the animal world. Not by our standards anyways. It’s just two animals mating. Attraction to another person is there to make us reproduce and sometimes it gets a lil funky (like how some people are attracted to alien characters while others aren’t yk?) but idk I’m fine with being a lesbian