One of the many things I hate about breeders is when they talk about the "instinctual drive" to have children. I won't deny, we have drives, but I think it's a whole lot simpler than that. We have drives to eat, sleep, poop/pee and we have a drive to FUCK.
Mother Nature made fucking feel good so we'd reproduce ourselves, period. Just like after the birth, Mother Nature floods the female with feel-good hormones so she'll bond with the baybee and not toss it in the nearest dumpster. I hate it when Breeders wax on about how this is some spiritual experience from Gawd and how they are Better People.
Animals fuck because it's instinctual. Humans want to fuck because it's instinctual. However, humans have a cerebral cortex, which presumably gives us the ability to rise above our animal impluses and NOT DO SOMETHING if it isn't a good idea.