Chimpanzees have rhythm, and language

Human capacity for language and music-making may not be as unique as previously thought, say primatologists. Wild chimpanzees use call combinations to add nuance, mirroring human language complexity, and drum on tree buttresses to stay in touch.

Take language. All apes, including chimpanzees and humans, use calls to communicate.

For humans, those calls are combined into sentences to create infinite meanings. Linguistic rules define how these ‘words’ are understood in different sentence structures, says primatologist, Dr Cédric Girard-Buttoz of Germany’s Max Planck Institute. A key component of language is syntax, defining how word-order conveys meaning, he adds.  “Go ape’ and “ape goes” mean very different things.     

But a recent study on chimps, by Max Planck Institute primatologists, published in Science Advances has concluded that “the human capacity for language may not be as unique as previously thought.”

They recorded and analysed thousands of calls from three groups of wild chimpanzees in Taï National Park in Ivory Coast, West Africa, and analysed their capacity to combine pairs of calls to expand meanings.

Communications between most primates, other than humans, are typically single calls (called ‘call types’). Few species combine calls, with most of these designed to alert others to the presence of predators, says first author, Girard-Buttoz. But changes in meaning delivered by combined calls are not well understood, he adds, and may provide insights into the origins of human language.

Primatologist Dr Michael Wilson, of the University of Minnesota, USA, clarifies: “If some features of chimpanzee communication resemble language, we can study chimpanzees further to find clues for why those features evolved.”

“If chimpanzee communication doesn’t share much in common with human language, then the key steps in language evolution must have occurred after our lineages separated (around 7.9 million years ago) for reasons unique to our human lineage.”  Wilson was not involved in the study.

The Taï National Park chimpanzees didn’t disappoint, showing real creativity in call combinations. Four distinct strategies were used to tweak call meanings, with individual calls strung together in 16 different two-call combinations, echoing core human language principles.

One call might mean “feeding”, another “resting”, the combination meaning “feeding while resting”. Or single ambiguous call might mean “feeding or travelling”, but the inclusion of an aggression-related call narrowed the meaning down to “travelling”.      

The chimps also created new meanings using combinations of unrelated calls — ‘idioms’. A “resting” call might be added to one meaning “affiliation”, when the chimp was nesting.

Far from just the dramatic, “look out, lion!” moments reported in previous studies, chimps were using complex communication in everyday situations.

“Our findings suggest a highly generative vocal communication system, unprecedented in the animal kingdom, which echoes recent findings in bonobos, suggesting that complex combinatorial capacities were already present in the common ancestor of humans and these two great ape species,” says Girard-Buttoz.

Chimpanzees also have rhythm

(Video) Chimp demonstrating drumming on trees

But chimp communication is not limited to calling. They also have rhythm, says wildlife biologist,  Dr Vesta Eleuteri of the University of Vienna who lead a separate study, recently published in Current Biology.  

First author Eleuteri, and her team, found that chimps drum on the buttresses of trees to tell group members where they are in their dense rainforest habitat. Buttresses are those thin, high roots, like rocket fins. The drumming is rhythmic and varies with group.

The work was based on a 24-year dataset on chimp behaviour in Taï National Park, and in reserves in Uganda, Tanzania, Guinea and Senegal.

“Each chimpanzee has their own unique drumming style, and that drumming helps to keep others in their group updated about where they are and what they’re doing—a sort of way to check-in across the rainforest,” she says.

“What we didn’t know was whether chimpanzees living in different groups have different drumming styles and whether their drumming is rhythmic, like in human music.”

“Making music is a fundamental part of what it means to be human—but we don’t know for how long we have been making music,” says coauthor Dr Cat Hobaiter of the University of St Andrews, Scotland.

“Showing that chimpanzees share some of the fundamental properties of human musical rhythm in their drumming is a really exciting step in understanding when and how we evolved this skill. Our findings suggest that our ability to drum rhythmically may have existed long before we were human.”

Both studies show that there is something special about hominid communication, as Buttoz says.

He concludes that either complex communication was already emerging in our last common ancestor with chimps and other great apes, or that we have underestimated such complexity in other animals, which demands further study.  

Chimpanzees converse at the same speed as humans