Babies sometimes laugh and sometimes cry. It doesn’t take a genius to decode the meaning of these sounds. But it isn’t quite as straightforward to decipher the meaning, if any, of an infant’s babbles. And humans a little older can make the same sounds regardless of how you actually feel—you’re able to say “I’m hungry” whether you’re ravenous or just gorged yourself.

Scientists think that the ability to make the same sounds across a range of emotional states is critical to language development. They also believe it to be uniquely human, because in previous studies of animal communication, researchers only observed fixed vocalizations. For example, bonobo chimpanzee pant-laughs and threat barks are tied to a specific emotion or behavior.

But the new study finds evidence that bonobos in the wild are also capable of flexible vocalizations. Bonobos have a specific call type, a “peep” that they use independent of emotional context. They peep while eating, travelling, grooming, resting, engaging in sexual activity, and even during shows of aggression.

Because peeps, like a baby’s babbles, don’t convey meaningful information on their own, bonobos need to combine them with other calls and environmental context to supply meanings. Previously, researchers thought this type of complex, language-like comprehension was unique to humans. The study is in the journal PeerJ. [Zanna Clay, Jahmaira Archbold and Klaus Zuberbuhler, Functional flexibility in wild bonobo vocal behavior]

Bonobos are our closest evolutionary relatives, so it’s possible that the functional flexibility of human speech appeared in a common ancestor. This discovery adds to the growing pile of evidence that we’re not quite as special as we’ve long believed—and that our furry cousins may be even closer to us than we thought.

—Diana Kwon

[The above text is a transcript of this podcast.]

[Bonobo sounds courtesy of Zanna Clay.]