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The Evolution of Language - Page 6
Language and Speech
Language is a complex phenomenon with origins that are difficult to trace. Certain aspects of language, though not without controversy, are better suited to empirical investigation. Speech is one example because it requires some physical properties that can be measured in, or at least partially derived from, the fossil record.
Phillip Lieberman has investigated the origin of speech for many years and has used this research to form hypotheses about the evolution of language. Lieberman suggests that speech improved greatly about 150,000 years ago when the larynx descended into the throat. According to the work of Lieberman and his colleagues, this descension improved the ability of early homonids to make key vowel sounds. Whereas the Neanderthals had a vocal tract similar in many respects to that of a new born baby, the elongated pharynx of a modern adult human is thought to enable production of a more perceptible repertoire of speech sounds. Lieberman suggests that though Neanderthals probably had some form of language, they may have failed to extend this language because they lacked the physical apparatus for producing a more sophisticated set of speech sounds. The theory that the modern human vocal tract is better suited for production of vowels has, however, recently been called into question by Louis-Jean Boe.
Figure1. Comparison of the supralaryngeal vocal tracts in a new born infant,
Neanderthal, and an adult human.
But the strongest part of Lieberman's argument is evolutionary rather than strictly phonetic. He points out that the descension of the larynx into the throat makes humans much more susceptible to choking than any other mammal. It is unlikely that such a dangerous adaptation would have evolved unless there was some strong selective advantage provided by it. Since the larynx contains the vocal cords and is critical for speech, it seems likely that Lieberman's hypothesis is correct in that this change somehow improved speech and that improved speech gave a distinct selective advantage, even if his hypothesis about what the exact improvements to speech were turns out to be incorrect.
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