The human mind is an unlikely evolutionary adaptation. How did humans acquire cognitive capacities far more powerful than anything a hunting-and-gathering primate needed to survive? Alfred Russel Wallace, co-founder with Darwin of evolutionary theory, saw humans as "divine exceptions" to natural selection. Darwin thought use of language might have shaped our sophisticated brains, but his hypothesis remained an intriguing guess--until now. Combining state-of-the-art research with forty years of writing and thinking about language evolution, Derek Bickerton convincingly resolves a crucial...