Chimpanzee Language - Is it a model for a primative language in early hominids

There has been a lot of online interest in the paper The Meanings of Chimpanzee Gestures by Catherine Hobaiter & Richard W. Bryne, which has just been published in Current Biology. The abstract ends: Here we present the first systematic study of meaning in chimpanzee gestural communication. Individual gestures have specific meanings, independently of signaler identity, and we provide a partial “lexicon”; flexibility is predominantly in the use of multiple gestures for a specific meaning. We distinguish a range of meanings, from simple requests associated with just a few gestures to broader social negotiation associated with a wider range of gesture types. Access to a range of alternatives may increase communicative subtlety during important social negotiations.

The researchers claim that they have decoded 66 different gestures whose meaning is the same whichever ape was making a gesture. For instance if a mother shows the sole of her foot to a baby it means "climb on me", while touching an arm is a request asking to be scratched. Interestingly chewing leaves is an invitation for sexual attention. Apparently several gestures can be strung together to represent more complex exchanges.

For the time being I feel rather frustrated, as the full paper is behind a paywall, and I would really like to assess the strength of the research for myself - rather than being dependent on the first wave of press release news reports. However there has been plenty of earlier work which establishes that a social animals such as the chimpanzee must be communicating, and I am sure that if there are any weaknesses in the current paper comments will soon turn up on various blogs elsewhere. 

However if wild chimpanzees in Uganda have a language of over 50 gestures it is interesting to  think how many gestures (or simple vocal sounds) would an early hunter-gather hominid need to be able to organise hunting by ambush or describing the location of a food source, in addition to normal social interactions. I would have thought a hundred different signals relating to actions and the ability to name a hundred objects would prove a powerful survival tool - and is not much more than appears to have been demonstrated in chimpanzees. Such a language could be far more primitive than the proto-language that is believe to have preceded all modern languages. 

Of course my estimate is only a guess. Has anyone done any research on the size of vocabulary needed to plan and execute a complex hunt?