Apes talk in a ‘language’ that humans can understand, study suggests. But why?

BRENDAN RASCIUS

January 25, 2023

Gary Stewart/AP

It turns out you don’t have to be Jane Goodall to understand apes.

Even untrained humans can decipher ape communication, including gestures related to grooming and sex, according to a new study published on Jan. 24 in the journal PLOS Biology.

The findings suggest humans may be able to tap into shared ancestral knowledge preserved long after our evolutionary split from apes, researchers said.

As part of the study, 5,656 participants were asked to watch a series of 20 videos displaying gestures from chimpanzees and bonobos, our closest living ancestors. Only common gestures with confirmed meanings were shown in the experiment.

Some participants, in addition to the videos, were also provided a one-line description of each gesture for context.

Afterwards, participants chose the meaning that they thought best matched each gesture from a multiple choice list.

Among some of the gestures presented in the videos were the “Big Loud Scratch,” which means an animal wants to be groomed, and the “Object Shake,” which signals a desire to have sex, researchers said.

Participants accurately interpreted the meaning of the gestures at a rate “significantly higher than expected by chance,” researchers said.

“Overall they had 52% accuracy when they just saw the gesture action, and 57% when they were told what happened before the gesture,” Dr. Kirsty Graham, a coauthor of the study, told McClatchy News. “If they were randomly clicking we’d expect about 25% accuracy.”

As to why untrained humans can decode ape signals, researchers are not sure, though they have ventured several guesses.

It’s possible apes and humans just happen to share the ability to interpret meaningful signals due to general intelligence and other visual clues, researchers said. After all, some gestures resemble the actions that they want to happen.

It’s also possible that the shared lexicon is inherited biologically from a common ancestor, illustrating “deep evolutionary continuity between” human and ape communication, researchers said.

“The main takeaway is that we now have a clearer idea where humans fit into the great ape gesture picture,” Graham said. “It seems to be a shared communication system across great apes and one that was likely used by our last common ancestors.”

Though researchers disagree about the exact timetable, recent studies indicate humans ancestors diverged from those of chimpanzees and bonobos about eight million years ago.

If you want to take a try at recognizing ape gestures, the test can be taken online here.