The human brain is an extraordinary organ. It has allowed us to walk on the moon, to discover the nature of matter and life, and to play chess almost as well as a computer. But this virtuosity raises a puzzle. The brain of Homo sapiens achieved its modern form and size between 50,000 and 100,000 years ago, well before the invention of agriculture, civilizations, and writing in the last 10,000 years. Our foraging ancestors had no occasion to learn astrophysics or to play chess, and natural selection would not have rewarded them with more babies if they had. How, then, did our outsize brain evolve?
展开▼
