Humans can instinctively understand our “great ape” cousins through hand gestures – even though we do not use the movements anymore, scientists found.
We share the same “sign language” – despite being separated from a common ancestor that roamed earth 10 million years ago.
Chimps and bonobos use similar bodily motions to communicate with each other, scientists said. And humans retain an understanding of these subtle gestures – even though we no longer use them ourselves, according to new research.
The discovery of gestures used by great apes provided the first evidence of intentional communication outside human language. They serve multiple purposes from initiating grooming and contact to sexual intercourse.
It suggests primate gestures with shared meanings extend to humans and could be biologically inherited, experts discovered.
Dr. Kirsty Graham, of the University of St Andrews and the lead author of the study, said: “All great apes use gestures.
“But humans are so gestural – using gestures while we speak and sign, learning new gestures and pantomiming, iconic gesturing used to communicate without speech.”
Over 80 such signals have now been identified, and many are shared across non-human apes, including distantly related species such as chimpanzees and orangutans. Despite being more closely related to chimpanzees and bonobos, they are no longer thought to be present in humans.
In an online game, 5,500 participants were tested on their understanding of the 10 most common. They were asked to view 20 short videos of ape gestures and select from four possible answers.
The volunteers performed significantly better than expected by chance, correctly interpreting the meaning more than 50 percent of the time. Providing contextual information about what the apes were doing only marginally increased the success rate.
Video playback experiments have traditionally been used to test language comprehension in non-human primates. The study reversed the principle to assess human skills at reading the minds of their closest living relatives for the first time.
Results suggest that although we no longer use these gestures, we may have retained an understanding of the ancestral communication system. Dr. Graham added: “It is really hard to pick out shared great ape gestures just by observing people.
“By showing participants videos of common great ape gestures instead, we found people can understand these gestures. It suggests that they may form part of an evolutionarily ancient, shared gesture vocabulary across all great ape species including us.”
Our ability to understand specific great ape gestures may be inherited, scientists said. Otherwise, humans and other great apes could share an ability to interpret meaningful signals because of their general intelligence, physical resemblance and similar social goals.
Bonobos, an endangered species from Central Africa, closely resemble chimpanzees but are more slightly built.
The study was published in the journal PLOS Biology.
Produced in association with SWNS Talker.
