Ever since the origins of both linguistics and evolutionary biology in the 19th century, scholars have noted the similarity between biological evolution and language change. Yet until recently neither linguists nor biologists have developed a model of evolution general enough to apply across the two fields. Even in linguistics, the field is split between the historical linguists who study change in language structure, and the sociolinguists who study social variation in the speech community. "Explaining language change" represents the first thoroughly worked out framework for language evolution, building on the pioneering ideas of Richard Dawkins and David Hull in biology and philosophy of science. Its central thesis is that the locus of language change is the utterance in social intercourse. Linguistic innovations emerge from the remarkable complexity of communication in social interaction. Once innovations occur, they are propagated through the equally complex social structures of the speech communities we participate in. "Explaining language change" provides a framework for assessing current theories of language change, and advances new ideas about grammatical reanalysis, conventional and nonconventional use of language, the structure of speech communities, language mixing, and the notion of "progress" in language change. "Explaining language change" reintegrates sociolinguistics and historical linguistics, weaving together research on grammatical change, pragmatics, social variation, language contact and genetic linguistics.