Monkeys, despite their many biological similarities with humans, lack our capacity for speech. Now, a new study demonstrates that the macaques are anatomically able to produce all of the sounds needed for human speech, suggesting that the human brain, not the human vocal system, is responsible for our species’ unique ability to speak. Their research was published last week (December 9) in Science Advances.
“Now nobody can say that it’s something about the vocal anatomy that keeps monkeys from being able to speak,” said Asif Ghazanfar, coauthor on the study and professor of psychology at Princeton University, in a press release. Instead, “it has to be something in the brain” that restricts monkey speech to guttural noises.
Ghazanfar and his colleagues recorded X-ray video of macaques creating sounds and tracked the movement of their lips, tongue, and larynx.Next, they plugged those data into a computer model that translated the range of movements into a range of possible sounds. They concluded that the scope of macaque vocalization is theoretically wide enough to produce human speech. The authors therefore posit that the absence of human-like speech among monkeys owes to a neurological shortcoming, not an anatomical one.
“This suggests that what makes people unique among primates is our ability to control the vocal apparatus, not the apparatus itself,” Thore Jon Bergman, an evolutionary biopsychologist at the University of Michigan, who was not involved with the work, told The Christian Science Monitor.
“Now the interesting question is, what is it in the human brain that makes it special?” Ghazanfar said, in the press release: