When finding different varieties of food chimpanzees will give a distinct grunt that is recognised by other chimps. Originally scientists believed chimps elicited these calls to show excitement about the food and held no control over what call was made.
This discovery was only made when researchers were able to witness the introduction of two groups of adult chimps. This occurred when the resident chimps of Edinburgh Zoo in the UK met a group from Beeske Bergen Safari Park in the Netherlands.
Before meeting each other the two troops had different grunts for apples and a different preference for them. After three years of living together the chimps from the Netherlands used a similar grunt to the Edinburgh chimps.
Scientists discovered by taking recordings of the grunts produced in 2010 before the chimps meet just after integration in 2011 and then in 2013. The calls did not change in 2011 but once the groups had begun to bond and some strong friendships evolved the call structures converged.
This completely changes current thinking that the acoustic structure of non-human primates is fixed and a product of excitement. This was seen as the difference between non-human vocalisations and language.
Dr Katie Slocombe, who led the York University’s department of Psychology team that worked on the project said, “An extraordinary feature of human language is our ability to reference external objects and events with socially learned symbols, or words. These data represent the first evidence of non-human animals actively modifying and socially learning the structure of a meaningful referential vocalisation.”
“Our findings indicate that primate referential call structure is not simply determined by arousal, and that the socially learnt nature of referential words in humans is likely to have ancient evolutionary origins,” she added.
The University of Zurich’s, Dr. Simon Townsend explained, “These findings might shed some light on the evolutionary origins of these abilities. The fact that both humans and now chimpanzees possess this basic ability suggests that our shared common ancestor living over 6 million years ago may also have been socially learning referential vocalisations”