Humans have retained a memory of the gesture 'language' used by other great apes such as chimpanzees, a study has revealed.
Online tests show that we still retain a memory of gestures used by great apes – the discovery of which provided the first evidence of intentional communication outside human language.
More than 80 such signals have now been identified, according to University of St Andrews researchers.
Many of these gestures are shared across non-human apes, including distantly-related apes such as chimpanzees and orang utans.
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Kirsty E Graham, of the University of St Andrews, said: "All great apes use gestures, but humans are so gestural – using gestures while we speak and sign, learning new gestures, pantomiming etc – that it's 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 that people can understand these gestures, suggesting that they may form part of an evolutionarily ancient, shared gesture vocabulary across all great ape species including us."
Watch: One of the 20 short videos of ape gestures viewed by study participants
The researchers tested people's understanding of the 10 most common gestures used by chimpanzees and bonobos via an online game.
More than 5,500 participants were asked to view 20 short videos of ape gestures and select the meaning of each gesture from four possible answers.
They found that participants performed significantly better than expected by chance, correctly interpreting the meaning of chimpanzee and bonobo gestures over 50% of the time.
Video playback experiments have traditionally been used to test language comprehension in non-human primates, but this study reversed the paradigm to assess humans' abilities to understand the gestures of their closest living relatives for the first time.
The results suggest that although we no longer use these gestures, we may have retained an understanding of this ancestral communication system.
The study's authors said it remains unclear whether our ability to understand specific great ape gestures is inherited, or whether humans and other great apes share an ability to interpret meaningful signals because of their general intelligence, physical resemblance, and similar social goals.