I'm one of the people who think that humans are naturally pretty violent and that modern society constrains this tendency. I think that when tribes fought with each other it usually had a very bloody outcome. Many people disagree and think humans are naturally peaceful and that modern society has corrupted us into becoming more violent. The noble savage vision of humans.
I've often heard and read that when hunter gather tribes fought it was mostly ceremonial and conflict would generally end when the first person was killed. The thing that strikes me about this vision, is that it is still extremely violent but modern standards!
Assuming this view of tribal war is true, and these confrontations happened every couple of years, most people would end up seeing several of their tribe members killed in these ceremonial battles over their lifetimes, which if you scaled up to modern populations would result in astronomical death rates.
America is a violent place by developed country standards with a murder rate of about 10 per one hundred thousand people per year. Having that murder rate in a hunter gatherer society would mean that a typical person would never know anyone who was killed.
The noble savage account is still pretty damn savage.