The oldest clear-cut evidence for lethal group violence by humans dates back not millions or hundreds of thousands of years but only 13,000 years. Moreover, as an excellent recent article on this Web site points out, tribal societies in regions such as the U.S. Southwest did not fight continuously; they lived peacefully for centuries before erupting into violence. These patterns are not consistent with behavior that is instinctual or "hardwired."
Restrepo, Junger's film on American soldiers, is supposed to be magnificent and I'm planning to see it. But John Horgan is disturbed by Junger's thesis, explicated not in the movie but his accompanying book, War, and puts forth his own counter-argument that humans are not hardwired to go to war, nor men universally excited by it.