" To be sure, there are hunter-gatherer societies that don’t exhibit the elaborately organized violence denoted by the term “war.” But often what turns out to be lacking is the organization, not the violence. The warless !Kung San were billed in the title of one book as The Harmless People, yet during the 1950s and 1960s, their homicide rate was between 20 and 80 times as high as that found in industrialized nations.114 Eskimos, to judge by popular accounts, are all cuddliness and generosity. Yet early this century, after westerners first made contact with a fifteen-family Eskimo village, they found that every adult male had been involved in a homicide. One reason the !Kung and most Eskimo haven’t waged war is their habitat.115 With population sparse, friction is low. But when densely settled along fertile ground, hunter-gatherers have warred lavishly. The Ainu of Japan built hilltop fortresses and, when raiding a neighboring "

― Robert Wright , Nonzero: The Logic of Human Destiny