Some monkeys are physically capable of speech. Their throats have all the hardware required to form words. The one thing they lack is software—these macaques haven't yet developed the brain circuits required to speak. This, says new research out of Princeton University, suggests that the human brain is what made it possible for us to talk to each other like we do.
"Now nobody can say that it's something about the vocal anatomy that keeps monkeys from being able to speak," study author Asif Ghazanfar says. "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."
This opens up the next step of research: Finding out just what it is that makes the human brain so special, says Ghazanfar.
Using x-ray video, Ghazanfar and his team studies the movements of the vocal gear of macaque monkeys to find out how they work together. They used the data gathered from the movement of the monkeys' tongues, larynxes, and lips to build a computer model of how the primates might sound if they spoke.
We form words in two basic stages. First the sound is generated by the larynx, and then we shape the words in our mouths. For example, we make the same sound for the English words "bit," "bet," "bat," "but," and "bought," shaping the vowel sound with our mouths. To hear how much the shape of our mouth alone can change sound, try this experiment. Play some music on your phone, and point the speaker up into your mouth, then make the vocal shapes "wow," "wee," etc., and listen to the changes in how the music sounds. It's pretty powerful.
By feeding the actual sound of a macaque grunt into the computer and shaping it into words using the model of its vocal anatomy, the researchers found that the monkeys are capable of producing intelligible sounds, including full sentences. The result can be clearly understood, although when you listen to the simulation above, in which a monkey says "Will you marry me?" you'll be glad they can't speak—it's pretty creepy.
These findings could help us better understand how humans evolved speech, especially the interplay between brain software and physical hardware. Just as long as researchers aren't kept awake at night by the spooky sound of monkeys proposing to them.