LONDON: Researchers have shown that monkeys produce well differentiated proto-vowels, an advance that pushes back earlier estimates of when speech evolved in animals by about 2,00,000 years.
The review study, published in the journal Science Advances, mentioned the theory of the “descended larynx”, according to which the larynx — commonly called the voice box — must be in a low position to produce differentiated vowels before speech can emerge.
According to the researchers, including those from CNRS in France, monkeys, which have a vocal tract anatomy similar to humans, had a higher larynx, and could not produce differentiated vocalisations.
But based on the current study, they said, speech may have emerged 200,000 years earlier than previous estimates.
The current study is a review of existing literature on the evolution of speech.
It notes the work of two pairs of researchers, in the 1930s-1950s, who had tested the possibility of teaching a home-raised chimpanzee to speak, at the same time and under the same conditions as their baby, but all their experiments ended in failure.
Explaining this result, in 1969 in a long series of articles a US researcher, Philip Lieberman, proposed the theory of the descended larynx (TDL).
Lieberman compared the human vocal tract to monkeys, and showed that these have a small pharynx — related to the high position of their larynx — whereas in humans, this organ is lower. (AGENCIES)
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