Bonobos speak like human babies, say scientists

Researchers say bonobos communicate with high-pitched calls that require context to understand – much like human babies do.

Michael Probst/AP
A three-day-old bonobo baby sleeps on the belly of its mother Kutu at a zoo in Frankfurt, Germany, July 21, 2015.

What do bonobos and babies have in common? They both use high-pitched "peeps" to express emotions.

An international research initiative has found that bonobos, a species of great ape found only in the Democratic Republic of the Congo, communicate like human infants. Their closed-mouth peeps can take on a variety of meanings in different contexts, according to a study published Tuesday in the journal PeerJ.

In other words, the building blocks of language may predate humanity.

Along with the common chimp (Pan troglodytes), bonobos (Pan paniscus) are the closest extant relatives of modern humans. Lead author Zanna Clay was studying these endangered apes in their native Congo when she picked up on their peeps – short, high-pitched, and made with closed mouths.

Dr. Clay, a biologist at the Université de Neuchâtel, was surprised by the frequency of these calls. She and her colleagues soon realized that the peeps were used in a wide array of situations to reflect an entire emotional spectrum. In positive and neutral contexts, the peeps were acoustically indistinguishable.

"Bonobos peep in just about every context you can imagine," Clay says in an interview. "They peep when they're traveling, feeding, grooming, resting, nest building, playing, aggression, alarm – you name it. This is striking because bonobos also produce many other calls which are much more fixed in their apparent use and function."

Primates, birds, and other animals are known to use "fixed calls" – vocalizations that are specific to a context or emotional state. Bonobos bark to alarm their troops of predators, laugh when playing, and scream to display aggression. But peeps are function-flexible, making for more complex communication. Before developing language skills, human babies use similar sounds, known as "protophones."

"In humans, protophones are the building blocks of speech, in that they vary in function across different emotional states and contexts," Clay says. "This contrasts with fixed calls in human babies, such as laughter and crying, which resemble typical primate calls. The peep seems to be a rather exceptional call in the bonobo repertoire in its degree of flexible usage."

According to Clay, these calls could represent a major evolutionary transition in primate communication. The shift from fixed to flexible signaling was an important stop on the road to human speech.

"Although humans are unique in terms of our amazing speech and language capacities," Clay says, "the foundations underlying these abilities appear to be already present in the last common ancestor we share with great apes. The findings suggest the existence of an intermediate stage between fixed vocal signalling seen in most primate calls and fully fledged flexible signalling in humans."

She added, "The more evidence we gather from studies of our great ape relatives, such as bonobos, the more we learn that many capacities thought to be uniquely human actually have their foundations firmly rooted in the primate lineage."

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.