Historical linguistics commonly invokes the child as the principal agent of change. Using this as a starting point, the authors address diachronic language change against a background of insights gained from extensive research into mono- and bilingual language acquisition. The evidence shows that children are remarkably successful in reconstructing the grammars of their ambient languages so the authors reconsider a number of commonly held explanatory models of language change, including language contact and structural ambiguity in the input. Based on a variety of case studies, this innovative...