Nang, do you consider it natural to crap yourself, or is it natural to have some control over your bowels? What about your bladder? Is drinking water from an open source (glass, pond, river, etc) natural, or is it against nature? Is a lion catching and killing an animal natural? All of these are, by your definition, learned actions. Babies can't control themselves, so they are toilet trained. Babies have to be shown how to drink from something other than a nipple or bottle at a young age. Lion cubs are taught how to hunt by the rest of the pride. I'd say that crapping, drinking, and killing/eating are all natural things. I sincerely doubt that even ancient man just crapped himself or took a leak while standing on his grass and mammoth fuzz bed.
I would say that deviant sexual behavior is not natural. I would say that certain relationships are not natural. I'd say that, by definition, abortion is certainly not natural. But sex is, for the most part, a natural desire.
I'm a walking enigma.