Typological hierarchies are widely perceived as one of the most important results of research on language universals and linguistic diversity. Explanations for typological hierarchies, however, are usually based on the synchronic properties of the patterns described by individual hierarchies, not the actual diachronic processes that give rise to these patterns cross-linguistically. This book aims to explore in what ways the investigation of such processes can further our understanding of typological hierarchies. To this end, diachronic evidence about the origins of several phenomena described...