Why Humans Talk and Other Primates Don’t – 08/12/2022 – Science

The vocal folds of human beings are the simplest of all primates — and, paradoxically, this was one of the factors that allowed the emergence of the complexity of spoken language in our species. It seems contradictory, but this is what a large comparative analysis of the vocal apparatus of monkeys and the Homo sapiens.

“Many studies have been done on the anatomy of the vocal tract, but people tended to pay less attention to the detailed structure of the vocal folds, which are the 1 cm or 2 cm long pieces inside the larynx that vibrate when we speak and sing. “, says Tecumseh Fitch, an American researcher who works at the University of Vienna and is one of the coordinators of the new research. “In our species, they are very simple, mere rounded bands of fabric.”

According to the author of the survey, which has just appeared in the specialized journal Science, in non-human primates, in addition to the folds themselves, there are small structures on top of them, known as vocal membranes or vocal lips, in the form of thin strips.

“It was already known that some species, such as chimpanzees and rhesus monkeys, had these tiny structures, but there was no systematic knowledge about their presence or absence in all primate groups”, explains Takeshi Nishimura, from the Primatological Research Institute at Kyoto University, which also signs the study.

The first step by Fitch, Nishimura and their colleagues was therefore to do this systematic mapping. The result is that the Homo sapiens in fact it is the stranger in the nest. Of the more than 40 species of primates analyzed —from those closest to us, such as chimpanzees, gorillas and orangutans, to the animals of the New World that we can find in Brazil, such as golden lion tamarins and capuchin monkeys—, we are the only without the vocal membranes, which are present, in different configurations, throughout our family.

In the next step of the work, the researchers directly observed the behavior of the structures during the passage of air through them – exactly the process that produces the sounds of the vocalizations of the animals and of the human speech. Analyzing what happens in the vocal tract of animals such as chimpanzees, rhesus monkeys and squirrel monkeys (the latter also native to Brazil), the difference between non-human and human primates became clear, as Fitch explains.

“When the vocal membranes vibrate, they cause the calls made by the monkeys to become louder and more high-pitched, but also less stable. The likelihood that they acquire irregularities that resemble screams is higher,” he says. “That is, losing these membranes and being only with the vocal folds makes the individual acquire a deeper, more melodious voice and easier to control. He becomes a precursor of Elis Regina”, jokes the specialist.

And it is at this point, the researchers propose, that the evolutionary leap forward of anatomical change likely resides. For them, the narrower and more controllable range of sounds derived from the simple vocal folds of humans and their ancestors would be ideal for producing the “alphabet” of vowel and consonant sounds — usually a few dozen — that languages ​​we know employ. .

The change in the shape of the vocal folds was not the magic wand stroke that produced the complex language we know today. Several other evolutionary changes contributed to this unique ability of humans, including changes in the brain that allowed control of delicate movements of the vocal tract and the ability to associate sounds and senses.

It also remains to be seen when and how the simplest vocal folds in our lineage appeared. “If we can determine when the loss happened through genomic analyses, for example, the reason for this loss may become clearer,” says Nishimura. “But our current work already demonstrates that it was important in adapting to speech.”

About Raju Singh

Raju has an exquisite taste. For him, video games are more than entertainment and he likes to discuss forms and art.

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