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. 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.