The ubiquity of acoustic lips did not necessarily mean that they influenced the sounds their owners produced. So Dr. Nishimura’s group removed the larynxes from three dead chimpanzees and attached them to simulated lungs. They did the same with six rhesus macaques that had been euthanized for other approved experiments. In all simulations, the vocal folds and vocal cords vibrate together. Mathematical models of other primate larynxes have yielded similar results.
In their paper, the researchers suggest that the absence of vocal cords in humans—and their complex vibrations—was a key factor in the evolution of language in our species. Vibrating in exquisite isolation, our vocal cords allow for the subtle changes in inflection and register that characterize our own speech. We reason and reason, plead and suggest, all in a controlled manner.
“This study shows that evolutionary changes in the larynx were necessary for the evolution of spoken language,” said Dr. Nishimura.
Dr Randall added: “This suggests, or reinforces, that there is a very different shift in strategy from human communication to non-human primate communication. Human language does not target emotional responses, but you do understand their minds. Trying to change — you’re killing the cognitive and idiosyncratic system.”
Still, Dr. Randall said, primates often speak softly and subtly, and humans often communicate through shouts. He recommended a “healthy skepticism” in deriving the origins of complex speech and language from anatomical findings. “I think they’ve just highlighted the fact that this membrane loss in humans is central to our ability to produce these stable vocal fold vibrations, which underlie the production of speech sounds. ,” They said.
Harold Gozoles, a psychologist at Emory University who wrote a Accompanying commentary On the recent paper, agreed. “It’s basically impossible to determine causation here,” he said. “It may be a necessary step in the evolution of language, but it remains to be seen whether it’s important at all.”
Dr. Gozolis said the research was most notable for its comparative analysis of primates and its ability to yield evolutionary insights from simple anatomy, often hidden from plain view. “Language is clearly more than the sum of its parts,” he said. “It’s unlikely that we’re ever going to have a completely satisfactory explanation.”