Copyright © 1999 Massachusetts Institute of Technology
The question of how language evolved has never been a respectable one. In the nineteenth century it motivated so much wild speculation that the Société de Linguistique de Paris banned all discussion on the topic -- and many academics today wish this ban were still in place. Over the last thirty or so years, however, findings from psychology, evolutionary biology, and linguistics have radically changed the way that scholars approach this issue, leading to some surprising insights and opening up areas of fruitful empirical investigation.
For one thing, proposals that language is entirely a cultural innovation, akin to agriculture or bowling, can be safely dismissed. Historical linguistics gives no support to the speculation that language was invented once and then spread throughout the world; instead, the capacity to create language is to some extent within every human, and it is invented anew each generation (Pinker 1994). This is most apparent from studies of creolization; children who are exposed to a rudimentary communication system will embellish and expand it, transforming it into a full-fledged language within a single generation -- a CREOLE (Bickerton 1981). A similar process might occur in all normal instances of LANGUAGE ACQUISITION: Children are remarkably proficient at obeying subtle syntactic and morphological constraints for which there is little evidence in the sentences they hear (e.g., Crain 1991), suggesting that some capacity for language has emerged through biological evolution.
Could this capacity have emerged as an accidental result of the large brains that humans have evolved, or as a by-product of some enhanced general intelligence? Probably not; there are people of otherwise normal intelligence and brain size who have severe problems learning language (e.g., Gopnik 1990), as well as people with reduced intelligence or small brains who have no problems with language (e.g., Lenneberg 1967). Furthermore, the human language capacity cannot be entirely explained in terms of the evolution of mechanisms for the production and comprehension of speech. Although the human vocal tract shows substantial signs of design for the purpose of articulation -- something observed by both DARWIN and the theologian William Paley, though they drew quite different morals from it -- humans are equally proficient at learning and using SIGN LANGUAGES (Newport and Meier 1985).
How else could language have evolved? Modern biologists have elaborated Darwin's insight that although natural selection is the most important of all evolutionary mechanisms, it is not the only one. Many traits that animals possess are not adaptations, but emerge either as by-products of adaptations ("spandrels") or through entirely nonselectionist processes, such as random genetic drift (Gould and Lewontin 1979). Natural selection is necessary only in order to explain the evolution of what Darwin (1859) called "organs of extreme perfection and complexity," such as the heart, the hand, and the eye. This is because only a selectionist process can evolve biological traits capable of accomplishing impressive engineering tasks of adaptive benefit to organisms (Dawkins 1986; Williams 1966). Although there is controversy about the proper scope of selectionist theories, this much at least is agreed on, even by those who are most cautious about applying adaptive explanations (e.g., Gould 1977).
Does language show signs of complex adaptive design to the same extent as organs such as the hand and the eye? Many linguists would claim that it does, arguing that language is composed of different parts, including PHONOLOGY, MORPHOLOGY, and SYNTAX, that interact with one another, as well as with perceptual, motoric, and conceptual systems, so as to make possible an extraordinarily complicated engineering task -- the transduction of thoughts into speech or sign. The conclusion that language decomposes into distinct neural and computational components is supported by independent data from studies of acquisition, processing, and pathology (Pinker 1994).
Based on these conclusions, some scholars have argued that language has evolved as a biological adaptation for the function of communication (Newmeyer 1991; Pinker and Bloom 1990). Others have proposed instead that the ability to learn and use language is a by-product of brain mechanisms evolved for other purposes, such as motor control (Lieberman 1984), social cognition (Tomasello 1995) and internal computation and representation (Bickerton, 1995) -- and that such mechanisms have been exploited, with limited subsequent modification, for speech and sign.
To put the issue in a different context, nobody doubts that the acquisition and use of human language involves capacities we share with other animals; the interesting debate is over whether the uniquely human ability to learn language can be explained entirely in terms of enhancements of such capacities, or whether much of language has been specifically evolved in the millions of years that separate us from other primates. The study of the communication systems of nonhuman primates is plainly relevant here (e.g., Cheney and Seyfarth 1990) as is the study of their conceptual and social capacities (e.g., Povinelli and Eddy 1996).
The more we learn about the cognitive and neural mechanisms underlying language, the more we will know about how it evolved -- which aspects are adaptations for different purposes, which are by-products of adaptations, and which are accidents (Bloom 1998). Perhaps more importantly, we can gain insights in the opposite direction. As Mayr (1983) points out, asking about the function of a given structure or organ "has been the basis for every advance in physiology." And although one can ask about function without considering evolutionary biology, an appreciation of how natural selection works is necessary in order to discipline and guide functional inquiry; this is especially so for the quite non intuitive functional considerations that arise in the evolution of communication systems (Dawkins and Krebs 1978; Hauser 1996). To the extent that language is part of human physiology, exploring how it evolved will inevitably lead to insights about its current nature.
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Copyright © 1999 Massachusetts Institute of Technology