By Jody Bourton

Earth News reporter



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Bonobos have been filmed appearing to 'say no' by shaking their heads, report scientists.

On a number of occasions, bonobos were filmed using side to side head movements to prevent others from doing something they did not want them to do.

In one film a mother is seen shaking her head to stop her infant playing with its food.

This may reflect an early precursor to head-shaking behaviour amongst humans in one of our closest relatives.

The study has been published in the journal Primates.

Disapproving look

"In bonobos, our observations are the first reported use of preventive head-shaking," say Ms Christel Schneider from the Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.



This would raise the question of whether these gestures reflect a primitive precursor of the human 'no' head-shake



Ms Christel Schneider

Max Planck Institute, Germany



Ms Schneider undertook the study with Dr Josep Call of the Max Planck Institute and Dr Katja Liebal from Freie Universität, Berlin, Germany.

Ms Schneider recalls how the videos captured at Leipzig Zoo in Germany show a bonobo mother shaking her head in disapproval when her infant plays with some food.

"Ulindi, tried to stop her infant, Luiza, from playing with a piece of leek. Since Luiza took no notice despite repeated attempts to stop her, Ulindi finally shakes her head towards the infant," she says.

Ulindi eventually throws the leek away whilst the infant still tries to reach for it, the researchers report.

'No' bonobo

African great apes such as bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) are known to use head gestures such as nodding, bowing and shaking to communicate with other group members.

Bonobos are already known to use head-shaking to initiate interactions with other members of the group, such as playing.

However, this is the first study to film and observe an ape shaking its head in a negative context to stop or prevent other bonobo behaviour.

The Germany-based scientists observed the behaviour whilst studying bonobos as part of wider study on the communication of great ape infants.

Using video recordings they studied the gestures and behaviour of bonobos, chimpanzees, gorillas and orangutans in six European zoos.

During the study, they witnessed four individual bonobos shaking their heads in this way on 13 different occasions.

Previously only anecdotal reports have noted individual chimpanzees shaking their head to signal 'no'.

Sophisticated ape

The researchers write how bonobos use a wide range of head gestures compared to chimpanzees, and are considered to be more sophisticated at using their head to signal meaning.

Such sophisticated communication systems may emerge because of the apparently tolerant, cooperative and egalitarian societies that bonobos live in, with their diffuse hierarchies and complex social structures.

In this way, bonobos may have developed the preventative head-shake to say 'no' and negotiate conflict situations.

The researchers are cautious to say that they cannot be sure the bonobos definitively mean 'no' when they shake their heads this way.

But it remains the best explanation so far.

More detailed research is now needed to fully establish the functional role of all forms of head gestures across ape species, they say.

The discovery may also provide a unique insight into our own head-shaking tendencies, they suggest.

"If future research can confirm the use of preventive head-shaking in our closest living relatives, the bonobos and chimpanzees, then this would raise the question of whether these gestures reflect a primitive precursor of the human 'no' head-shake," says Ms Schneider.

In short, humans may be hardwired to shake their heads to say no.

However, as Ms Schneider told BBC News, it should be noted that head shaking is not always associated with the negative.

"In some cultures, e.g. Bulgaria, head-shaking can mean yes," she adds.