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Washington — Scientist We have identified evolutionary changes in vocal organs that distinguish people from other primates that may underpin an essential human ability: the ability to speak.
On Thursday, researchers examined the vocal organs known as the larynx in 43 species of primates and found that, unlike apes and monkeys, humans have an anatomical structure called the vocal membrane (a small ribbon of ribbon). ) was shown to be absent. extension of the vocal cords.
They also noted that humans lack balloon-like laryngeal structures called air sacs, which may help apes and monkeys produce loud, resonant calls and avoid hyperventilation.
According to researchers, the loss of these tissues resulted in a stable human vocal source. This is important for the evolution of speech, the ability to use distinct sounds to express thoughts and feelings. This laryngeal simplification enabled humans to have excellent pitch control in long, steady speech sounds, they said.
"We argue that the more complex vocal structures of non-human primates may make it more difficult to control vibrations precisely." Published in Science. Research http://www.science.org/doi/10.1126/science.abm1574.
"Although the vocal membranes enable other primates to sing louder and higher than humans, they suffer from vocal breaks and noisy vocalizations." Irregularities will become more common,” said evolutionary biologist and study co-author W. Tecumseh Fitch of the University of Vienna, Austria.
The larynx is a hollow tube in the throat that connects to the top of the trachea and contains the vocal cords and is used for speaking, breathing, and swallowing.
"The larynx is the organ of the voice, producing the signals we use to sing and speak," Fitch said.
Humans, like monkeys and apes, are primates. The evolutionary lineage that led to our species, Homo sapiens, diverged from the lineage that led to our closest living relative, the chimpanzee, about 6 to 7 million years ago, after which a change in the larynx occurred.
Only living species were included in the study, as these soft tissues do not tend to be preserved in fossils. This also means that it is unknown when the change was made.
Fitch said that laryngeal simplification may have arisen in a human precursor called Australopithecus, which appeared in Africa about 2.4 million years ago. Homo sapiens originated in Africa over 300,000 years ago.
Researchers have studied the larynx of apes such as chimpanzees, gorillas, orangutans and gibbons; Old World monkeys such as macaques, guenons, baboons and mandrills; studied anatomy.
This evolutionary simplification of the larynx was crucial, but ``it alone was not capable of speech,'' Fitch points out, noting that other anatomical features may have changed over time. It was pointed out that it is important for speech over time. Changes in the position of the larynx.
The vocalization mechanisms of humans and non-human primates are similar, with air from the lungs causing vibrations in the vocal cords. The sound energy thus generated passes through the pharynx, oral cavity, and nasal cavity and emerges in a form governed by the filtering of specific frequencies determined by the vocal tract.
"Speech and language are definitively related, but not synonymous," says primatologist and psychologist Harold Guzules of Emory University in Atlanta, who accompanies the study. wrote a commentary http://www.science.org/doi/10.1126/science.add6331 in the journal Science. } Paradoxically, the increasing complexity of human speech followed the simplification of evolution. I think the loss of certain traits could open the door to new adaptations," Fitch said.
(reported by Will Dunham, edited by Rosalba O'Brien)
