Why can’t primates like chimpanzees talk or sing like humans?
Scientists had previously believed that the key to the problem lay in the developmental changes brought about by the evolution of the human brain, but more recently the focus has shifted to the anatomical changes in the vocal cords. Changes in the structure of the vocal cords may be responsible for our complex sounds.
Recently, a team of researchers from Japan and Europe found that the evolution of the structure of the human larynx has contributed to the stable vocalization of our communication. Unexpectedly, however, this change was not due to an increase in a particular vocal fold structure, but a loss of structure. The study was published in the journal Science.
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The simplification of the structure of the vocal cords—which feels paradoxical—included in the increasingly complex human communication. The vocal cords of most primates have a thin, ribbon-like sound membrane, while the disappearance of such air sacs in humans has been observed in chimpanzees and other apes, which may be due to the stable voice quality of humans when speaking and singing , the reason for the controllable tone.
Takeshi Nishimura, a researcher at the Center for the Evolutionary Origin of Human Behaviour at Kyoto University and lead author of the paper, explains that their work is largely based on the work of the late Dr. Sugio Hayama. Dr. Sugio Hayama’s research results show that changes in vocal cords must affect the evolution of spoken language. The Nishimura team took their work to a new level, proving that the simpler the shape of the vocal cords, the easier it is to control their vibrations.
Senior author Tecumseh Fitch from the University of Vienna explained that the team discovered by studying a large number of monkeys and apes that the thin acoustic membrane in their larynx is unique to non-human primates. Based on research by the computer modeling research group, the acoustic membranes allow non-human primates to produce their characteristic sounds, while humans are able to produce beautiful sounds because of the loss of these membranes during evolution.
Young Japanese macaques cooing | KyotoU WRC/Hideki Sugiura
“Inside the throats of vocalizing chimpanzees and monkeys, we saw their vocal membranes vibrate actively and produce loud, erratic sounds like a scream,” says Tecumseh Fitch.
Isao Tokuda of Ritsumeikan University is concerned with the nonlinear dynamics of animal vocalization. According to his research in the field of vocalization mechanisms in chimpanzees, the vibratory organization on the vocal cords may increase the degree of freedom of vibrations, resulting in frequent sound instability .
“By avoiding this instability, humans may have acquired a stable source of sound that accelerated the evolution of language,” says Jake Dunn, an evolutionary biologist at Anglia Ruskin University. “Reconstructing evolutionary history through contrastive methods. , the results show that despite our common ancestor, if all non-human primates have a vocal membrane but humans do not, then we may have lost this feature in late evolution.”
According to Christian T Herbst, an Austrian speech scientist and former scholar at Kyoto University, the relationship between the reduction in the complexity of the throat structure and the improvement in the ability to create and transmit rich language information is precisely a “ability to generate complex speech information from the throat. Migration to the brain”.
Ole Næsbye Larsen of the University of Southern Denmark said: “Comparisons between extant species are often used to infer evolutionary traits that cannot be recorded in fossils, such as animal behavior. Previously, our video recordings of laryngeal movements during vocalization in squirrel monkeys, Now there seems to be support for the hypothesis of the evolution of human oral language abilities.”
Nishimura concludes: “Of course, other changes are required in acquiring language, including in our brains, but this anatomical simplification may have accelerated the process of our singing and speaking more accurately.”
references
[1] https://ift.tt/cxtgAMw
[2] https://ift.tt/nzVIF2B
Compilation: Oasis
Editor: Jin Xiaoming
Typesetting: Yin Ningliu
Title image source: KyotoU WRC/Hideki Sugiura
research team
First/Corresponding Author Takeshi Nishimura: Ph.D., Institute of Primate Research, Kyoto University
Corresponding author W. Tecumseh Fitch: Ph.D., Department of Behavioral and Cognitive Biology, University of Vienna
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Paper information
Publish the journal Science
Posted on August 11, 2022
Thesis title Evolutionary loss of complexity in human vocal anatomy as an adaptation for speech
(DOI: https://ift.tt/lPoVBsh)
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