Human evolution presents a puzzle. Nothing seems to explain the sudden takeoff of the last 45,000 years—the conversion of just another rare predatory ape into a planet dominator with rapidly progressing technologies. Once "progress" started to produce new tools, different ways of life and burgeoning populations, it accelerated all over the world, culminating in agriculture, cities, literacy and all the rest. Yet all the ingredients of human success—tool making, big brains, culture, fire, even language—seem to have been in place half a million years before and nothing happened. Tools were made to the same monotonous design...