The biggest mystery in anthropology is what ignited the cultural revolution 45,000 years ago in Europe, when its upper half was covered with an ice-sheet. The Archaics, Neanderthals, and recently-arrived Cro-Magnons suddenly exploded in a flurry of cave paintings, body adornments, carved Venus figures, intentional burials, and new portable tools.

This revolution spread from one human species to another, each of whom had enjoyed large brains tor a hundred thousand years without any prior cultural activity.