The expression of aggression is conditioned both biologically and culturally and it can be learned. On the other hand, proper upbringing can complete… - Jerzy Vetulani

We humans are already at this moment artificially reared, with the provision of basic life needs and without having to fight for it. We would even, as a species, be able to survive a long period of total glaciation of the Earth.

As a result of brain evolution, humans managed to develop much more efficient and less risky forms of gaining food than most other carnivorous and omnivorous terrestrial mammals. We do not need now, like our distant ancestors, to go through long periods on the verge of hunger and use all suitable occasions for immoderate consumption "in reserve." Today, in a civilized world, thanks to effective production, we have enough food, and we could consume it rationally, in quantities necessary for efficient functioning. But after our ancestors, we have a deeply ingrained habit of "gorging", especially if the food is attractive. Together with prosperity, the world has been overtaken by an epidemic of obesity and overweight.

Sexual intercourse consumes time, requires much effort, absorbs a huge part of energy. But it gives such dose of pleasure, that all of these defects don't matter.