It's hard to imagine that for most of the timeline of human beings, for most generations of our ancestors, there was no war. That's because people were spread too thinly, and there wasn't enough surplus to support protracted campaigns. There was violence, but there were no soldiers. Eventually populations reached a certain density, in a wave which spread outwards, and every society had to become a war economy. Any society which was not ready to gear up for war would be (and was) obliterated, or driven out to the most marginal environments. Technology, food surpluses, social roles, moral values, all had to be directed to enable permanent war-readiness.
And that's us, we have been living in permanent war readiness for thousands of years, without any breaks. It's hard to imagine the impact that has had on us, because there is no place on earth, no people left, who haven't been affected by that.
merrymaia also told me that Ehrenreich thinks our emotional experience of war is not based on predation, but on being prey. That is enemy soldiers are not, in emotional terms, deer (that we hunt) but wolves (that hunt us). Our emotional coping with war uses the instinctual drives which orignally evolved to protect our communities against animal predators. For hundreds of thousands of years we 'made war' on cave bears and sabre tooth tigers, and extinct mega-leopards. It was exciting and affirming to defeat the lion that might have eaten the children. That's why war has an aspect which is thrilling and warming.
PS - if I misinterpret Ehrenreich or maia, that's my bad not theirs.