Imagine the strong selective pressure as humans moved to larger social groups and agrarian societies. These were ruled by strongmen interested above all else in most cases in collecting the highest taxes from a compliant population. Anyone too fierce, fearful or combative would be ostracized at best, killed at worst.
Even today, prisons and mental institutions are filled with non-conformist, anti-social people who in many cases are not allowed to reproduce.
Even today, prisons and mental institutions are filled with non-conformist, anti-social people who in many cases are not allowed to reproduce.