A startling conclusion emerges from deficits affecting language: There are no language-only hereditary disorders. And the reason for that is predicted by the theory of language evolution here – namely that there could not be such a deficit because there is no language-specific part of the brain. Language is an invention. The brain is no more specialised for language than for toolmaking, though over time both have affected the development of the brain in general ways that make it more supportive of these tasks.
