We may not be able to strike up a conversation, debate politics or chat about the meaning of life with other great apes, but our ability to understand one another might be greater than once thought.
Researchers have discovered adult humans can discern the meaning of gestures produced by bonobos and chimpanzees, despite not necessarily using such gestures themselves.
“It seems that this is an ability that’s retained in our species as well [as other apes],” said Dr Kirsty Graham, first author of the research from the University of St Andrews, in Scotland.
Writing in the journal PLoS Biology, Graham and her colleague, Dr Catherine Hobaiter, said that intentional communication, in which an individual conveys meaning to another, is a feature of human languages but is rarely seen in other species.
Given it is implausible that intentional communication cropped up in humans through a single recent genetic leap, it is probable a simpler form was used by our evolutionary ancestors. Indeed, modern ape species today are known to use gestures to communicate their goals. Now the researchers have revealed that adult humans show a surprising level of understanding of such gestures.
The results emerged when the pair analysed data from 5,656 participants who took part in an online game in which they were shown 20 videos of chimpanzees and bonobos making 10 of their most common gestures, such as “groom me”, “give me that food” and “let’s have sex”, alongside an illustration of the gesture.
While some of the gestures had one meaning, others had several – with the correct meaning dependent upon the context of the gesture.
Participants were randomly allocated either to watch the gestures with text on what the apes were up to before the gesture – such eating or resting – or without this information, and were asked to select the correct meaning from four possible answers.
The findings showed that participants did better than chance at correctly interpreting the meanings of chimpanzee and bonobo gestures, whether or not contextual information was given, with an average success rate of 57% if information was given and 52% if not. What was more, the results held whether or not the gesture had just one, or multiple, meanings.
“The gestures and vocalisations [of our ancestors] likely co-evolved into the modern human gesture and human language that we have today,” said Graham. “Studies like this, and [the research in infants], give us more confidence in saying that this is probably something that our last common ancestor [with other great apes] would have been able to do.”
While the team say it is unclear quite how such gestures are understood across great ape species, including humans, one possibility is that understanding is hardwired, while another is that it arises as a result of a similar body, social goals and capacity to figure out meaning – possibly helped by some gestures resembling the desired outcome.
“It [could be] more of an inherited capacity rather than an inherited vocabulary,” Graham said.