Why is there variation rather than nothing?

Although variation and heterogeneity are generally recognized as a characteristic of linguistic usage, they are hardly conceived as a fundamental dimension of grammar. Introducing a distinction between an exemplum linguistics and a datum linguistics, we show that the history of the language sciences, both conceptually and descriptively, is organized around opposing conceptions of what a linguistic fact is. While Generative Grammar and its practitioners are clearly examples of the first, corpus linguistics illustrates the second conception. The upsurge of datum linguistics and of usage based models since the beginning of the 21st century allows for a fundamental reassessment of the functional role of variation in language. We show that while the biolinguistic program rests on the negation of the sociocultural framing of the language faculty and denies any functional impact of communicational competence in shaping language and grammars, constructional approaches and usage-based linguistics make room for a Darwinian sociocultural conception. In such a conception, communication is a leading force in the emergence and stabilization of human linguistic competence, both diachronically and synchronically. In this approach, variation and heterogeneity are to be seen as core factors in shaping language. Thus, as argued some 50 years ago by Weinreich, variation and heterogeneity are to be regarded as structurally functional, and as fundamental dimensions of language.