The Evolution of Language by W. Tecumseh Fitch

Author:W. Tecumseh Fitch
Language: eng
Format: epub, pdf
Publisher: Cambridge University Press
Published: 2010-04-13T16:00:00+00:00

particularly important in infant mammals, for it allows them to suckle and breathe at the same time, and can be seen as an adaptation to lactation and suckling (Wall and Smith, 2001). Humans start life just like other mammals, with a high larynx, and a human infant can suckle and swallow while leaving the larynx in a high, sealed position, drastically decreasing its chances of choking on milk. But at about age three months, the larynx begins to slowly descend from this position, and by the age of four years has reached a low position where the nasolaryngeal seal is no longer possible (Sasaki et al., 1977). In adult humans the larynx has descended to a position far below the hard palate, and we can no longer even touch the epiglottis to the velum, much less insert it to form a sealed breathing tube. If we adult humans inhale while swallowing, we choke (sometimes to death; Heimlich, 1975).

Given its centrality in many discussions of language evolution (e.g. Laitman and Heimbuch, 1982; Wind, 1983; Lieberman, 1984; Pinker, 1994b; Carstairs-McCarthy, 1999), this unusual human characteristic warrants detailed attention. Other aspects of human vocal anatomy have changed since our divergence from chimpanzees: we gained a sexually-dimorphic larynx and we lost the laryngeal air sacs present in all of the other great apes (Fitch, 2000b). But the issue of the “descent of the larynx” has played a far more central role in recent debates about language evolution.

The idea that peripheral anatomy allows, or prevents, speech is a very old one. Aristotle, noting the intelligence of dolphins, suggested that their inability to speak resulted directly from vocal anatomy: “its tongue is not loose, nor has it lips, so as to give utterance to an articulate sound” (Aristotle, 350 BC). Eighteenth-century Dutch anatomist Peter Camper suggested that the air sacs of orangutans prevented speech in great apes (Camper, 1779). The central question was framed nicely by Jan Wind: “let us assume that a whole chimpanzee vocal tract would be transplanted into a human individual, while its nervous system would remain human” (p. 626, Wind, 1976). What would be the speech output capabilities of such a hybrid? Wind himself concluded it would be little different from a modern human, a conclusion shared by Darwin (Darwin, 1871). Others have argued that a modern human vocal tract is necessary for modern human speech (Lieberman et al., 1972; Laitman and Reidenberg, 1988), and many have found these arguments convincing (e.g. Donald, 1991; Pinker, 1994b; Carstairs-McCarthy, 1999). Today, the field is divided on the topic, but the majority of researchers accept the idea that a chimpanzee's phonetic potential is considerably reduced, purely due to its peripheral vocal anatomy – and would be even were a human brain in control. Of course, scientific truth is not determined by majority vote. My goal in the following sections is to review what is known, in enough detail to allow readers to reach their own well-informed opinion.

The adult human vocal tract has long been known

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