Signs used by monkeys understandable by humans

Humans understand the “signs” or gestures that wild chimpanzees and bonobos use to communicate with each other.

That’s the conclusion of a video-based study in which volunteers translated monkey gestures. It was carried out by scientists from St Andrews University.

This suggests that the last common ancestor we shared with chimpanzees used similar gestures and that they were the “starting point” for our language.

The findings were published in the scientific journal PLOS Biology.

Lead researcher Dr Kirsty Graham from St Andrews University explains: ‘We know that all great apes – chimpanzees and bonobos – have about 95% of the gestures they use to communicate.

“So we already suspected that it was a common gesticulation skill that might have been present in our last common ancestor. But now we’re pretty sure that our ancestors started with gesturing and that it was co-opted into language.”

This study was part of an ongoing scientific mission to understand the language’s origin story by carefully studying communication in our closest ape cousins.

Chimpanzee communication signals

Chimpanzee communication signals

This team of scientists has spent many years observing wild chimpanzees. Previously, they discovered that great apes use a whole “lexicon” of more than 80 gestures, each of which conveys a message to another member of its group.

Messages such as “cleanse me” are conveyed with a long scratching motion; a pull of the lips means “give me that food”, and the tearing of the teeth with the teeth of the leaf strips is a chimpanzee flirting gesture.

Monkey translations

The researchers used video playback experiments because this approach has traditionally been used to test language comprehension in primates. In this study, they reversed the approach to assessing humans’ ability to understand the gestures of their closest living great ape relatives.

Volunteers watched videos of chimpanzees and bonobos gesturing, then selected translations from a multiple-choice list.

Participants performed much better than expected by chance, correctly interpreting the meaning of chimpanzee and bonobo gestures more than 50% of the time.

“We were really surprised by the results,” said Dr Catherine Hobaiter of St Andrews University. “It turns out that we can all do this almost instinctively, which is both fascinating from the perspective of the evolution of communication and really quite annoying as a scientist who has spent years training himself to do it,” she joked.

Gestures that humans can naturally understand may form part of what Dr. Graham described as “an evolutionarily old, common gesture vocabulary for all great ape species, including us.”

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