Vers la fin des années 1960, Philip Lieberman constate que le larynx de l’être humain adulte est situé plus bas que celui des singes dans le conduit vocal et formule sa théorie de la descente du larynx pour expliquer pourquoi l’humain peut parler et pas monkey. In other words, it is this peculiarity of the human larynx that allows us to produce the vowels i / a / ou that are found in all languages of the world. The theory is supported by the fact that the larynx has not yet descended in babies a few months old who are still unable to speak. And since what we knew about Neanderthals at that time led us to believe that he also had a non-descending larynx, we concluded that he also could not speak, and therefore language could not only appear in Homo sapiens About 300,000 years ago.
But since then we’ve been able to show that: a one-year-old is able to produce these famous vowels even if his throat isn’t in the “right place” yet; The position of the Neanderthal’s larynx was similar to that of a NeanderthalHomo sapiensAfter careful analysis of his neck bones. Observing baboons in the laboratory using new acoustic signal processing techniques showed thisThey have produced vowel-like sounds (Beautiful animation “Monkeys” by UrielHe also talks about it on pages 114-116).
So, 27 million years ago when the branch to turn down Distinguished from baboons and macaques, it is very likely that this common ancestor produced the same sounds as today’s baboons, by So from this point on, the vocal tract can be used for something other than breathing or swallowing..
Because we must remember that young mammals must suck and swallow their mother’s milk without choking, or they will die. It is the function of sucking and swallowing, involving the lips, tongue and pharynx, that is essential and allows milk to enter the stomach and not the larynx, trachea and lungs. Therefore, this anatomical conformation has carried over into the feeding function which has been reused, in reverse if one may say so, to speak. But this other use came with an increased risk of choking while eating, a trade-off that still allows us to produce more different sounds.
Having said that, speech is not just a poop as Lieberman believes, but it is also a matter of the brain. Because coordinating all the movements of the vocal apparatus for speech requires many cognitive abilities. It remains very difficult to determine whether regions involved in speech production also come from recycling associated with swallowing or whether other motor circuits have evolved (see “Monkeys,” pp. 117–119).
