The Human Swarm: How Our Societies Arise, Thrive, and FallThe epic story and ultimate big history of how human society evolved from intimate chimp communities into the sprawling civilizations of a world-dominating species If a chimpanzee ventures into the territory of a different group, it will almost certainly be killed. But a New Yorker can fly to Los Angeles--or Borneo--with very little fear. Psychologists have done little to explain this: for years, they have held that our biology puts a hard upper limit--about 150 people--on the size of our social groups. But human societies are in fact vastly larger. How do we manage--by and large--to get along with each other?