Gorillas don't ape each other - they know sign language from birth, say experts

http://www.dailymai l.co.uk/sciencet ech/article- 1139644/Gorillas -dont-ape- -know -sign-language- birth-say- experts.html

By Claire Bates

09 February 2009

Gorillas are born with an international sign language of gestures that they use to communicate.

The largest scientific study of the great apes revealed they had a repertoire of 102 different signals - more than any other mammal.

Many of these such as 'disco arm shake' and 'tapping other' were common in all the gorillas studied despite being in different continents.

The great apes can communicate with more than 100 hand gestures

The researchers from St Andrews University also found each gesture was carried out with close attention to their audience: silent signals were only given when other apes could see them.

Lead author Professor Byrne said: 'As we added more populations to the study, most gestures that had seemed specific to one individual or one site almost always turned up elsewhere.

'Any two populations are likely to differ a lot in the repertoire of gestures shown, but all are drawn from a very large, species-wide 'pool' of possible gestural signals.'

The team concluded that the gestures do not need to be learnt, because they are already part of the natural gorilla communicative repertoire.

The new work throws light on a puzzle in the behaviour of great apes. Several studies have found that apes are capable of the 'Do as I do' routine that children also enjoy, but their copies of human actions modelled for them are relatively inexact.

Professor Byrne explained, 'Dr Joanne Tanner and I studied a female gorilla that was able to do this, and we found that all her 'copies' of apparently novel human actions were really actions she'd done herself, sometimes years before: they matched the demonstrated actions pretty well, but not exactly.

'It was only because of Tanner's long-term data on the gorillas that we could find out what was going on.

'So we think that, just as in the case of communicative gestures, the fact that apes have a huge repertoire of actions can explain how they imitate human demonstrations and why their copies are usually inexact: they are 're-using' actions from their own repertoire, not learning new ones.'