What developmental disorders can tell us about the nature and origins of language.

Few areas in the cognitive sciences evoke more controversy than language evolution, due in part to the difficulty in gathering relevant empirical data. The study of developmental disorders is well placed to provide important new clues, but has been hampered by a lack of consensus on the aims and interpretation of the research project. We suggest that the application of the Darwinian principle of 'descent with modification' can help to reconcile much apparently inconsistent data. We close by illustrating how systematic analyses within and between disorders, suitably informed by evolutionary theory-and ideally facilitated by the creation of an open-access database-could provide new insights into language evolution.