The lack of these elements is what causes a stable vocal source in humans that is critical to the evolution of speech. This simplification of the larynx is what gave humans excellent pitch control with stable speech sounds that result in modern-day speaking.
“We argue that the more complicated vocal structures in nonhuman primates can make it difficult to control vibrations with precision,” told The Guardian primatologist Takeshi Nishimura of Kyoto University’s Center for the Evolutionary Origins of Human Behavior in Japan and lead author of the new paper.
“Vocal membranes allow other primates to make louder, higher-pitched calls than humans – but they make voice breaks and noisy vocal irregularity more common,” said evolutionary biologist and study co-author W Tecumseh Fitch of the University of Vienna.
Humans, on the other hand, use the larynx for talking, breathing, and swallowing.
“The larynx is the organ of voice, which creates the signal we use to sing and speak,” Fitch added.
Since the researchers only studied living species (because soft tissues are not preserved in fossils), they could not determine at what point in history these evolutionary changes were made.
The so-called laryngeal simplification could have appeared with the Australopithecus, which first appeared in Africa roughly 3.85m years ago, or later in our genus Homo, which first appeared in Africa about 2.4m years ago.
The scientists do note that the evolutionary simplification of the larynx “did not give us speech by itself”, Fitch explained, stating that other additional changes such as the position of the larynx took place to lead to speech.