This is where things get weird. Yes, humans are animals, and as far as I know (please correct me if I am wrong), they are the only species with the higher brain functions to change the way they think. Animals for the most part just go with their instincts. There's an instinct to f**k, and an instinct to eat. Humans, however, are an exception that can decide to not f**k or eat.
It's that exception that makes this a really odd discussion, because if we want to include human behavior when discussing what is natural, things get really complicated.