Humans continually search for that thing that makes us unique—the traits that distinguish us from base animals—but it seems the more we try to prove we’re superior, the more we find out we’re not that special. For example, the long-held tenet is that apes cannot vocalize like humans to create speech, but now some researchers think we might be wrong on that count.
The breakthrough came after Marcus Perlman of The Gorilla Foundation and Nathaniel Clark of the University of California, Santa Cruz studied 71 hours of video of Koko the gorilla interacting with her handlers.
“I went there with the idea of studying Koko’s gestures, but as I got into watching videos of her, I saw her performing all these amazing vocal behaviors,” said Perlman in a press release.
Koko was part of a project to see if gorillas could be taught sign language—and since its inception in 1972, many major discoveries have been made thanks to Koko. For example, she learned over 1,000 signs and can combine them to express new meanings she wants to convey, including emotional expressions. (When her pet kitten All Ball died, Koko signed, “bad sad bad” and “frown cry-frown” before crying herself. She also cried when her friend Robin Williams died.) Further, she can understand and respond to about 2,000 spoken English words.
However, the one breakthrough Koko never had involved controlling her vocal communication, as it was thought apes only made vocal noises reflexively, thanks to previous research.
“Decades ago, in the 1930s and ’40s, a couple of husband-and-wife teams of psychologists tried to raise chimpanzees as much as possible like human children and teach them to speak. Their efforts were deemed a total failure,” Perlman explained. “Since then, there is an idea that apes are not able to voluntarily control their vocalizations or even their breathing.”
Koko has control over her vocalizations
This notion fit nicely with a common theory of the evolution of language—that the human ability to speak is only found in us and not the non-human primates.
“This idea says there’s nothing that apes can do that is remotely similar to speech,” Perlman said. “And, therefore, speech essentially evolved — completely new — along the human line since our last common ancestor with chimpanzees.”
However, after Perlman and Clark examined the videos of Koko, they realized she was performing nine different—and voluntary—behaviors that required control over her vocalizations and breathing. Further, these behaviors were entirely learned; they are not part of the normal gorilla repertoire.
For example, when Koko wants treats, she can blow a raspberry into her hand. She can also blow her nose into a tissue, play wind instruments, blow onto a pair of glasses so she can clean them with a cloth, and mimic phone conversations by prattling wordlessly into a telephone.
“She doesn’t produce a pretty, periodic sound when she performs these behaviors, like we do when we speak,” Perlman said. “But she can control her larynx enough to produce a controlled grunting sound.”
Further, she has enough control over her larynx that she can cough on command—an especially impressive feat because it requires the larynx to be closed off entirely.
“The motivation for the behaviors varies,” Perlman says. “She often looks like she plays her wind instruments for her own amusement, but she tends to do the cough at the request of Penny and Ron [her caretakers].”
From this discovery, the evolution of the human ability to speak is pushed back much further, to around 10 million years ago—the time of our last common ancestor with gorillas.
“Koko bridges a gap,” Perlman says. “She shows the potential under the right environmental conditions for apes to develop quite a bit of flexible control over their vocal tract. It’s not as fine as human control, but it is certainly control.”
This study can be found in Animal Cognition.