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Auteur: Tecumseh FITCH

The Evolution of Language : A Comparative Biological Viewpoint

Abstract/Résumé: Humans are born with a capacity to acquire the language of their community that appears unparalleled in any other species. After centuries of speculation, and decades of unresolved debate regarding fossil hominids, the scientific study of the evolution of this capacity has recently received a powerful boost from two new types of biological data: comparative and genetic. Comparative data from a wide variety of nonhuman animals allows us to develop "cognitive phylogenies" for different mechanisms of language. Studying homology, we can pinpoint the origin of broadly shared traits in the vertebrate family tree, and estimate when they evolved. Studying analogy, we can locate cases in which similar traits have evolved independently, in separate clades like primates and birds. Such examples of convergent evolution allow us to test hypotheses about adaptive function and mechanistic prerequisites, and thus go beyond asking "when?" to ask "why?" certain traits evolved. I will illustrate these comparative principles with mechanisms involved in human spoken language, such as vocal imitation and the descended larynx. The second "new wave" of data comes from genes involved in speech and phonology, such as FOXP2, ROBO1 and DCDC2. Such genes affect neural development, and provide a window into the computational mechanisms involved in language. Again, comparative data from animals play a crucial role in helping us to understand the functional roles of such genes. Furthermore, genetic variability related to such language-related genes can be used to estimate the time during which unique human variants swept through an ancestral population, and thus to roughly date the origin of particular cognitive mechanisms. I discuss three leading models of language evolution can be tested using this approach, which might be dubbed "cognitive archaeology". Based on these two powerful new sources of empirical data, I suggest that the time is ripe for fundamental progress in understanding the evolution of the human language capacity, and with it progress in understanding human cognition more generally.