I argue for uniformitarianism (Mufwene 2001) in accounts of language evolution. Below, after dismissing a few myths about the development of creoles, I show how what we have learned to date about this case of language speciation prompts genetic linguists to reopen the books about language diversification in general and as a concomitant of language death in many cases. I adduce various examples from distant and recent histories to illustrate how population movements and contacts have been a critical ecological factor even in the cases of so-called "internally-motivated" change. The distinction between "internally" and "externally-motivated" language change boils down to a mere sociological contrast once contact is situated at the inter-idiolectal level, where interactions and negotiations between linguistic systems take place, regardless of whether or not xenolectal features participate in the feature pool. Ultimately, the same mechanisms of competition and selection that apply to linguistic features also apply to languages and dialects. Driven by the ecology of language use, the mechanisms roll the dice not only on how a particular language evolves under specific ecological conditions but also on the vitality of languages.
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