Because of its central role in human culture and cognition, language has long been a core concern in discussions about human evolution. Languages are learned and culturally transmitted over generations, and vary considerably between human cultures. But any normal child from any part of the world can, if exposed early enough, easily learn any language, suggesting a universal genetic basis for language acquisition. In contrast, chimpanzees, our nearest living relatives, are unable to acquire language in anything like its human form. This indicates some key components of the genetic basis for this human ability evolved in the last 5–6 Myr of human evolution, but went to fixation before the diaspora of humans out of Africa roughly 50 000 years ago. Darwin recognized a dual basis for language in biology and culture: ‘language is … not a true instinct, for every language has to be learnt. It differs, however, widely from all ordinary arts, for man has an instinctive tendency to speak, as we see in the babble of our young children; while no child has an instinctive tendency to brew