Humanity, as far as we can tell, is the only species on Earth capable of using language. That doesn’t mean other animals aren’t able of communicating through idiosyncratic means too. From cetaceans to non-human primates, sound and gestures are just some of the ways in which they “speak” – and, as revealed by a new PLOS Biology study, two of our closest relatives, bonobos and chimpanzees, share plenty of common, meaningful gestures.
The last common ancestor between these two great apes lived around 2 million years ago and ever since, the two creatures have evolved and diversified. Both belong to the same genus, Pan, but they belong to different species.
It’s long been known that both use gestures to communicate, and that a decent number of them were fairly similar. In fact, there’s even an audio-visual dictionary on hand to demonstrate this.
The study explains that, unlike most nonhuman animals, “great apes habitually engage in first-order intentional communication.” Using stares, grins, grunts, howls, gesticulation and more, these evolutionary cousins of ours can ask their friends to follow them, request an ally to scratch their back, or encourage an amorous friend to begin copulating with them.
An international team of researchers, comprised of neuroscientists and psychologists at the Universities of St Andrews and York, as well as a primatologist at Kyoto University, wanted to delve deeper into this chimpanzee chat and bonobo banter. Although it was known that 90 percent of the bonobo’s gestural repertoire overlapped with the chimpanzees, it wasn’t clear if the same overlap extended to inherent meanings.
Carefully observing gestures made by separate communities of bonobos and chimpanzees over time, they deduced their meanings by carefully judging how the recipients of the gestures tended to react. This way, the team avoided intuitively (and perhaps erroneously) interpreting the meanings behind the actions.
Comparing gestures used by both species, the team found a similarity much greater than would be expected by chance, both in terms of the physical form of the gestures, and, it appears, their meanings. The implications, of course, are that the two could effectively “talk” if they should ever meet in the wild.
“Bonobos and chimpanzees are separated by the Congo river, so they never encounter each other in the wild,” lead author Dr Kirsty Graham, a research associate at the University of York, told IFLScience. “But we think that because their gestures have such similar meanings, if they ever did meet they would be able to understand one another.”
There are some caveats that are certainly worth mentioning at this point. It’s not easy to tell whether animal signals have inherent meanings, rather than merely functions. Although the team’s method extracts meaning more effectively than earlier methods, it’s not perfect, so there’s a chance that some gestures remain lost in translation.
This study suggests that our wordless ancestors may have evolved these gestures as a form of interspecies communication, long before civilization took shape.
“What we're really interested in next is bringing humans into the picture,” Graham added. “Do young infants use any of these gestures before they start to acquire cultural gestures? Can human adults understand any of the chimpanzee and bonobo gestures?”