A group of French researchers has revealed that human speech is nearly 20 million years ago and it actually evolved at a time when our common ancestor lived with a monkey, who presumably had the capacity to produce vowel sounds. Until 2019, for about 50 years scientists believed in the theory of the "descended larynx" which stated that before speech can emerge, the larynx must be in a low position to produce differentiated vowels. Unlike humans, the monkeys have vocal tract anatomy that has the essential articulators (tongue, jaw, lips) but could not produce differentiated vocalizations with a higher larynx. As per an article in Science Advances, researchers at French National Center for Scientific Research (CNRS) and the Universite Grenoble Alpes, in collaboration with French, Canadian and US teams have found that monkeys produce well-differentiated "proto-vowels".
Louis-Jean Boe, lead author of the study wrote that the new study has shown that not only is the low larynx "not uniquely human" but also not necessary in producing those sounds. The production of differentiated vocalizations is not, therefore, a question of anatomical variants but of control of articulators, he wrote. This work leads us to think that speech could have emerged before the 200,000 years ago that linguists currently assert.
Researchers in the 1930s-1950s, tested the possibility of teaching a home-raised chimpanzee to speak, at the same time and under the same conditions as their baby. Yet it didn't work out. In order to find out the reason behind this, a long series of articles were written by US researcher, Philip Lieberman in 1969 proposing the theory of the descended larynx (TDL). The research showed that the monkeys have a small pharynx, related to the high position of their larynx, whereas, in humans, the larynx is lower. This anatomic block reportedly prevented differentiated vowel production. The new study adds to it stating that if the emergence of articulated speech is no longer dependent on the descent of the larynx, which took place about 2,00,000 years ago, the earlier speech emergence could have been as far back as at least 20 million years, a time when our common ancestor with monkeys lived, who already presumably had the capacity to produce contrasted vocalizations.