We can communicate with chimps. When put to the test, people can usually understand the meaning of ten common gestures used by chimpanzees.
Human infants also use some of the same gestures before they can talk, although we don鈥檛 yet know if their meanings are the same.
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The gestures may be the remnants of a basic sign language used by our last common ancestors with apes, says Kirsty Graham, who did the work while at the University of St Andrews in Scotland. 鈥淭his gestural communication is probably biologically inherited among the great apes 鈥� including humans.鈥�
One idea about language evolution is that we developed the ability to speak by building on a more primitive kind of sign language. To investigate, the St Andrews team have been recording the meanings of gestures used by gorillas, chimps and bonobos, a related species, to put together the online .
So far they have found about 70 gestures, with about 16 different meanings, as several gestures can convey the same meaning. Most are shared by the three great apes.
The researchers set up a website where members of the public could watch short video clips of ten common signs made by chimps and bonobos, and guess what each one meant from four options.
By chance they should have got a quarter of the answers right. But people did better than that, picking the correct answer 52 per cent of the time, and this rose to 57 per cent if they were given a brief description of the situation when the gesture was used.
Some gestures had success rates over 80 per cent, for instance, when a chimp strokes near its mouth, which means it is asking for food, says Graham, who presented the findings at the European Federation of Primatology meeting in Oxford this week.
In a , Adrian Soldati, also at St Andrews, looked for whether preverbal children used similar signals. 鈥淎dults don鈥檛 need to use gestures so much because spoken language is so powerful,鈥� he says. His team filmed 13 German and Ugandan infants between one and two years old when interacting with caregivers.
They defined gestures as discrete movements of the body during periods of communication that didn鈥檛 achieve anything physically 鈥� so it would not count if a child pulled their parent towards an object, for instance, but it would if they gave a small ineffectual tug. Sometimes the children seemed to be successful in achieving their goal, but not always.
The group recorded 52 kinds of gestures, about 90 per cent of which are also seen in chimps. Although they didn鈥檛 have enough material to systematically study if the children鈥檚 gestures meant the same as those of the apes, Soldati noticed a few such cases.
For example, if a child 鈥� or chimp 鈥� reaches out with their palm uppermost, they are asking for something, such as food or a toy. 鈥淭hey have this similar tool kit of gesture types that at least in some of the cases they used for similar goals,鈥� says Soldati. 鈥淲e kind of inherited this repertoire.鈥�
But Thibaud Gruber of the University of Geneva, Switzerland, says there could be other explanations for the way that adults can understand ape gestures. 鈥淗umans can also recognise vocalisations 鈥� for example, a strident high-pitched call signals danger 鈥� you don鈥檛 have to invoke [ancestry], acoustics explains it. Some of these gestures are pretty obvious and self-explanatory.鈥�
