We owe our big brains less to inventiveness than to conflicts of interest among social minds engaged in an arms race to be the best at manipulating others.

Humans like to think of themselves as unusual. We've got big brains that make it possible for us to think, and we think that we have free will and that our behavior can't be described by some mechanistic set of theorems or ideas. But even in terms of much of our behavior, we really aren't very different from other animals.

What drives the separation of groups of people into subgroups is the desire to control resources. We begin with a single culture, and over time the number of individuals within that culture expands.

Nothing in our evolutionary history specifically prepared us to live in large societies. Almost everything about the way culture works does.