Monkeys have the necessary anatomy to produce the sounds of human speech, but lack the brain connections that humans use to make words, research suggests.
A study that closely monitored with X-rays how a monkey’s mouth and throat moved in order to understand its full potential found that if a monkey’s brain was wired differently, they could make intelligible speech sounds.
The researchers then used their data to come up with a simulation of what it would sound like if an ape or monkey were able to say short phrases like, “Happy holidays.”
These findings throw doubt on the long-held assumptions on how humans evolved and developed their unique ability for speech, NPR reports. Tecumseh Fitch, a cognitive biologist at the University of Vienna, said,
What you’ll find in the textbooks is that monkeys can’t talk because they don’t have the appropriate vocal tract to do so.
He further explained, “That, I think, is a myth. My colleagues and I all get very tired of seeing this. But you see it in all the textbooks. Lots of popular books, and also scholarly books about the evolution of language, assume that in order to evolve speech we had to have massive changes in our vocal tract.”
Scientists used to look at the vocal tracts of dead animals to see what they could do. Fitch says humans have greatly underestimated the flexibility of other mammals.
His team tracked a long-tailed macaque named Emiliano as he produced a wide range of gestures and sounds, like lip-smacking, yawning, chewing, grunting and cooing. Using special equipment, they took rapid X-rays to capture the full range of motion in Emiliano’s vocal tract. They then fed their data to computer models to look into speech potential.
They found that monkeys would be physically capable of making the sound of five distinguishable vowels, which are the most common in languages. Humans could even clearly understand this speech, including a marriage proposal.
Fitch said the bottom line is that a monkey’s speech limitations are due to the way its brain is created. Monkey’s brains don’t have direct connections to the neurons that control the tongue and larynx, he said. Furthermore, monkeys don’t have the same wiring within the brain, specifically within the auditory cortex and the motor cortex. This makes them unable to imitate what they hear the way humans can.
The study was published in Science Advances.
