We may share a basic language with chimps
We seem to have a natural ability to communicate with chimps. When tested,
people can usually understand 10 common hand gestures used by
chimpanzees. Human infants use some of these same gestures before they
can talk, although we don’t know if their meanings are the same.
Some common hand gestures may be shared by all great apes
The gestures may be the remnants of a basic sign language used by our last
common ancestors with other apes, says Kirsty Graham, who did the work with
colleagues while at the University of St Andrews, UK. “This gestural
communication is probably biologically inherited
among the great apes
–
including humans,
” she says.
One idea about language evolution is that we developed the ability to speak
by building on a kind of sign language. To investigate, Graham and her
colleagues have been recording the gestures of gorillas, chimps and bonobos.
So far, they have found 70 or so, with about 16 different meanings, as several
gestures can convey the same message. Most are shared by these three great
apes.
The team set up a website called the Great Ape Dictionary where the public
could watch video clips of 10 common signs made by chimps and bonobos,
and choose what each one meant from four options.
52% of the time people can identify an ape hand signal’s meaning
By chance, they should get a quarter of the answers right.
But they picked
correctly 52 per cent of the time, rising to 57 per cent if given a brief description
of the situation in which the gesture was used. Some signals
– such as a chimp
stroking near its mouth, which means it is asking for food
–
were correctly
matched over 80 per cent of the time.
Graham presented the findings at the European Federation of Primatology
meeting in Oxford, UK.
In a previous study, Adrian Soldati at St Andrews
looked at whether preverbal children used such signals. “Adults don’t need to
use gestures so much because
spoken language is so powerful,” he says. He
and his team filmed 13 German and Ugandan infants between 1 and 2 years
old interacting with caregivers
They defined gestures as discrete movements during periods of
communication that
achieve nothing physically
– so it didn’t count if a child
pulled their parent towards an object, for instance, but it did if they gave a small,
ineffectual tug. Sometimes, the children seemed to succeed at 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’t have enough material to systematically
study if the children’s gestures meant the same as those of the apes, Soldati
noticed a few such cases.
For example, if a child
– or chimp – reaches out with palm uppermost, they are
asking for
something. “They have this similar toolkit of gesture types that, at
least in some of the cases, they used for similar goals,” says Soldati. “We kind
of inherited this repertoire.”
But there could be other explanations for the way adults can understand ape
gestures, says Thibaud Gruber
at the University of Geneva, Switzerland.
“Humans can also recognise vocalisations, for example, a strident highpitched
call signals danger. You don’t have to invoke [ancestry], acoustics explains it.
Some of these gestures are pretty obvious and self-exp
lanatory.”