Like humans, chimpanzees combine vocalizations into larger, meaningful communicative structures. The UZH researchers suggest that this ability could be evolutionarily older than previously thought.
A key feature of human language is our ability to combine words into compositional sentences, that is, where the meaning of the whole is related to the meaning of the parts. However, it’s not so clear where this ability came from or how it evolved.
Chimpanzees, our closest living relative, are known to produce a number of different vocalizations to manage their social and ecological lives, and in some circumstances combine these calls into larger sequences. By conducting carefully controlled experiments with wild chimpanzees in Uganda, researchers at the University of Zurich (UZH) demonstrated that chimpanzees understand these combinations.
Chimpanzees react more strongly to call combinations.
“Chimpanzees produce ‘alarm huus’ when surprised and ‘waa-barks’ when potentially recruiting conspecifics during aggression or hunting,” says Maël Leroux, a postdoctoral student at UZH’s Department of Comparative Language Sciences. , who led the study. “Our behavioral observations suggest that chimpanzees combine these calls when exposed to a threat where it is advantageous to recruit group members, such as when encountering a snake, but experimental verification has been lacking until now.”
The researchers presented the chimpanzees with model snakes and were able to get the call combination. Critically, the chimpanzees responded stronger to playbacks of the combination than when they heard just “alarm-huu” or “waa-bark.” “This makes sense because a threat in need of recruitment is an urgent event and suggests that hearing chimpanzees actually combine the meaning of individual calls,” adds study last author and UZH professor Simon Townsend.
Primate roots of compositionality
One important implication of the new findings is the potential light they may shed on the evolutionary roots of the compositional nature of language. “Humans and chimpanzees last shared a common ancestor approximately 6 million years ago. Therefore, our data indicates that the ability to combine meaningful vocalizations is potentially at least 6 million years old, if not older,” Townsend says. . “These data provide an intriguing insight into the evolutionary emergence of language,” Leroux added. In short, he suggests that compositionality originated before the appearance of language itself, although follow-up observational work and experimentation, ideally on other great ape species, will be essential to confirm this.
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