Grim linked to this interesting article about the development of institutional over personal violence. I think it is better to keep the discussion all in one place, so let's have it over at his site.
But just to get the controversy started, it bears a strong resemblance at first glance to the difference between Africa and China over the last thousand years or more, with the Middle East and Europe more like China, and New World populations along a wide range in the middle. Raiding, as opposed to pitched battles, overlaps this discussion.
Once Northern Europe, especially Scandinavians, had only warfare, not raiding to fear, they became more like bonobos. Which in that narrow range of centuries from the 17th to the 20th, made eminent sense. Life is safe. Food is becoming plentiful. Life is good. Warfare was intermittent and involved armies more than the general populace. That blew up in their faces in the 20th C, but one sees the point. In the 21st C the difference is now the internal population, not all of whom are bonobos anymore. That's one change.
And there's still the threat of war from the east, from Eursia, too. Even though culture persists, there is also constant change in the world, and the skills needed for survival change as well.