Apes and Humans Might Share Ancient Universal Body Language That Lets Them Understand Each Other

Chimpanzees and bonobos use gestures to initiate and change positions during grooming. Catherine Hobaiter

In addition to language, humans use a complex set of body movements and gestures to communicate with one another. Scientists also know that great apes, such as chimpanzees and bonobos—our two closest living relatives—use a system of gestures to convey meaning.

Now, new research published in the open-access journal PLOS Biology has shown that chimps and bonobos may be able to understand each other's body gestures. This suggests that great apes, including humans, might share a universal system of communication that could have first evolved in a common ancestor, millions of years ago.

For the new study, researchers from the University of York, Kyoto University and the University of St. Andrews examined videos of wild bonobos in Uganda to understand more about the meanings behind their gestures and compare them to those made by chimps. (The meaning of many chimp gestures is already well documented.)

To determine the meaning of each bonobo gesture, the researchers looked at the reaction that each body signal elicited in other bonobos. For example, a bonobo might present an arm to a second bonobo—who responds by climbing on the first's back, causing the first bonobo to stop gesturing. The researchers would infer from this exchange that the first bonobo was "satisfied" with the outcome and therefore that the meaning of the gesture is "climb on me."

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Using this method, the researchers created a kind of bonobo dictionary that documented 33 different types of gestures and their meanings.

When they compared the meanings of both the chimp and bonobo gestures, they found there was a substantial overlap, suggesting that the gestures were biologically inherited, according to the University of York's Kirsty Graham, lead author of the study.

In light of these findings, "it's likely that all great apes can understand at least some of this system of gestures," Graham told Newsweek.

"We know that gorillas share around 60 percent of the chimpanzee gestures and orangutans share around 80 percent. We don't know if they have the same meanings, but we're starting to look into it, and our hypothesis is that many of the meanings will be shared."

She continued, "And we've also just finished an online experiment seeing if humans understand any of the great ape gestures, by showing people videos of chimp and bonobo gestures and asking what they think the gestures mean. We haven't yet finished analysis, but we're hoping to be able to say which of the great ape gestures humans still seem to understand."

The University of St. Andrews's Richard Byrne, another author of the study, is also cautiously confident that great apes do share an ancient system of communication.

"I would point out that any imperfection in our knowledge of the gestural system is likely to make us underestimate how similar it is to that of others. We've found repeatedly that a gesture that seemed unique to one species later turned up in others," he told Newsweek.

"With large repertoires, like those of the great ape gesture system, imperfection in our knowledge is going to be the norm," he added. "So although we are cautious in how we put it now, it may be that the whole system of gestures eventually proves to be very similar in all great apes."