IOW, men who develop a technology that gives them an advantage, in this case probably food producing methods that allows them to maintain a more dense population, promptly invade their neighbors, kill the men and breed with their women.
History of the world in a nutshell. We are all descended from brutal conquerors and rapists. Because those who lost didn’t reproduce.
Not PC, so we have to pretend these interactions were peaceful. Why Darwinists in biology promptly abandon “survival of the fittest” when faced with human history is quite beyond me.
So this is why I have a mean streak?
People who A) come up with a more reliable way of feeding themselves and B) defend their food supply from the dumb and lazy neighbors wind up breeding out and absorbing those neighbors. Usually warfare isn’t required.
Apparently it’s still fun though, because evidence of the sacking of a town goes back way into prehistoric times, in more than one site.
The riverine civilizations came about because of a steady water supply and/or the use of irrigation. Better and regular diets meant that family size increased, infant mortality decreased, and so-called genetic bottlenecks arose as a consequence.
Property rights became systematized — bookkeeping, recordkeeping, accounting, surveying, writing — pushing nomadic herders (they had replaced hunter-gatherers during the preceramic eras in most places on Earth) out of sodbuster territory.
Standing armies became both possible (because of food surpluses) and necessary (for town defense and to avoid idle layabouts and louts).