Has bestiality always been historically so taboo? Why? It doesn't result in pregnancy; did it result in diseases? Why did humans evolve to get so repulsed from touching genitals with other species?

Ok to everyone talking about consent:
1. Consent wasn't really a strong concept in past cultures; you could rape your wife nbd but still not fuck an animal
2. Even if you use that, we still don't consider consent valid for non-sexual violations of animals