The idea that there is an unbridgeable gap between human language and animal communication has taken another hit. For many years it has been maintained that chimpanzees cannot change their vocal signals, so although the grunts vary in different populations, in any particular group they are fixed. Therefore their vocalizations were not at all like a proto-language. A new paper by Watson and others (citation below) documents change in the vocalization in chimpanzees.
Goodall has said, “the production of sound in the absence of an appropriate emotional state seems to be an almost impossible task for a chimpanzee”. The general consensus was that variation of vocalization depends on emotional not informational factors, and that manual gestures were relatively flexible and intentional, whereas vocal signals were fixed.
The new study shows that chimpanzees can change the grunt for a particular food in order to better communicate with another group that they have joined. They can learn vocal symbols in a social context.
This make a big difference to our understanding of our own language ability. The proposition that our close relatives lack some important ingredient in the make-up of their brains and that is why they did not evolve a proper language has become extremely weak. It cannot be assumed that language is such an obvious advantage that any animal that has not evolved language obviously is unable to. The other idea therefore becomes stronger – we have language because we are more cooperative and trusting than our cousins. Language use is risky. Once individuals can risk open communication within a society, language takes off in both cultural and biological evolution (fast, although it probably took a few hundred thousand years). It is likely that all the ingredients were there (in our common ancestor with chimpanzees) for a proto-language and all that was needed was the safety to talk.
Here is the abstract: “One standout feature of human language is our ability to reference external objects and events with socially learned symbols, or words. Exploring the phylogenetic origins of this capacity is therefore key to a comprehensive understanding of the evolution of language. While non-human primates can produce vocalizations that refer to external objects in the environment, it is generally accepted that their acoustic structure is fixed and a product of arousal states. Indeed, it has been argued that the apparent lack of flexible control over the structure of referential vocalizations represents a key discontinuity with language. Here, we demonstrate vocal learning in the acoustic structure of referential food grunts in captive chimpanzees. We found that, following the integration of two groups of adult chimpanzees, the acoustic structure of referential food grunts produced for a specific food converged over 3 years. Acoustic convergence arose independently of preference for the food, and social network analyses indicated this only occurred after strong affiliative relationships were established between the original subgroups. We argue that these data represent the first evidence of non-human animals actively modifying and socially learning the structure of a meaningful referential vocalization from conspecifics. Our findings indicate that primate referential call structure is not simply determined by arousal and that the socially learned nature of referential words in humans likely has ancient evolutionary origins.”
Watson, S., Townsend, S., Schel, A., Wilke, C., Wallace, E., Cheng, L., West, V., & Slocombe, K. (2015). Vocal Learning in the Functionally Referential Food Grunts of Chimpanzees Current Biology DOI: 10.1016/j.cub.2014.12.032