I listen to a science podcast "Big Picture Science" on a weekly basis. This week some scientist were talking about the very early times of humanity. They focused on skeletons found that indicated that the humans had died of violent homicides. As long as humans were hunter gatherers, the homicide rate among males was 15%. When we evolved to being stationary and engaging in agriculture and animal husbandry the homicide rate among males rose to 25%. This would be disputes over land, females, etc. Most disturbing was the discovery that when a male killed another male, he would go on to kill the other family members also.
Those of us here now are truly the survivors of the fittest.