Monkeys Could Talk Like Humans If Their Brains Didn’t Stop Them From Doing So

Unless you are living on the planet of the apes, you would know that nonhuman primates are incapable of emitting human-like speech. For the longest time, scientists attributed this to a difference in the anatomy of vocal tracts, suggesting that monkeys’ “acoustic vowel space” was more restricted than that of humans.

However, a new study based on experiments involving macaques — a genus of Old World monkeys — argues that the problem stems not from the vocal tract, whose capability has been “drastically underestimated,” but from a lack of adequate brain circuitry.

“This study shows that the anatomical capability to make a variety of sounds, as we do with speech, was present long ago,” Jon Bergman from the University of Michigan said in a statement released Friday. “This is useful for understanding the starting point for the evolution of language.”

For the purpose of this study, which appeared in the journal Science Advances on Friday, the researchers investigated the range of movements that the primate vocal anatomy could produce. They did so by reviewing X-ray videos of rhesus macaques and mapping the outline of their vocal tracts. This data was then used to create a computer model that simulated macaque speech.

Doing so revealed that macaques use roughly the same range of vocal tract movements as humans do during speech production, and could, if they had the neural capability, speak like humans.

Interestingly, the presence of human-like vocal tract in an old species such as the macaques suggests that this would also be present in newer species, including the chimpanzees. If so, scientists would need to look for reasons why this ability did not translate into the kind of speech sounds that humans produce.

“Now nobody can say that it's something about the vocal anatomy that keeps monkeys from being able to speak — it has to be something in the brain. Even if this finding only applies to macaque monkeys, it would still debunk the idea that it's the anatomy that limits speech in nonhumans,” study co-author Asif Ghazanfar, a professor of psychology at Princeton University, said in the statement. “Now, the interesting question is, what is it in the human brain that makes it special?”

That, of course, is a much tougher question to answer.