Comment by discoball

Sarcastically speaking, it all started with the division of labor between hunters and gatherers. If hunters had to gather too they wouldn't have had developed a specialization for killing other beings, and many of them would have preferred gathering to hunting due to the risk involved in the latter, so hunting would have been a fringe activity, not an institutionalized part of society (aka armies) Also, women and men who are not so driven by testosterone most likely gravitated toward gathering rather than killing, and so there we have the roots of sexism and machoism, with the assholes doing the killing and normal human beings relegated to "less strong" gatherers. And I believe natural hormones in meat affected the hunters own hormonal balance and pushed them toward more aggression, and the act of killing became normalized. Then we have technology being developed to increase the efficiency of killing other beings and eventually to increase the efficiency of killing other people. The tribes that engaged less in killing and more in gathering got wiped out by the ones that engaged more in killing than gathering. The End.