I am deliberately looking at military casualties, to highlight that tribal "military" casualties couldn't possibly be that high. I would guess that the fraction of deaths that were civilian was higher in both world wars than in tribal conflicts. Tribal conflicts are, AFAIK, almost always strictly men killing other men. Per capita comparison is distorted by the longer lifespan of people in the 20th century. Just having more people live past the age of 40 shouldn't, I'd think, make your age look more peaceful.