In this book, author Salikoko Mufwene offers a chronology of his views on language evolution as they have developed over the past 12 years. Mufwene understands the linguistic evolutionary process in terms of a language's external ecology – that is, its position relative to other languages with which it moves in and out of contact, the power relations among groups of different language varieties in the setting, and so on – as well as its internal ecology, or the coexistence in a given setting of the linguistic features, and their relative weight. Although Mufwene uses creole languages as a starting point, his purpose is to highlight general characteristics of language evolution; he argues that, in the essentials of language change, varieties such as pidgins and creoles differ little if at all from non-pidgins and non-creoles. To build his case, Mufwene draws from population genetics, seeing any given language not as an organism but rather as its own “species.”