Honestly, people have been doing that for a very long time. Male homosexual activity is documented in the early BC’s across the world. There are entire sections dedicated to anal penetration in the Kama Sutra for heterosexual anal penetration.

Given it’s not much of a leap for a horny brain to go “What if I stick it in here” I think it’s safe to say that humans have been going for that bootyhole since we were early hominids running from Pleistocene megafauna.