Screams, grunts, and rhythmic percussion: Chimpanzees combine sounds like human words

To unravel the origins of human communication, it's helpful to look at those who share more than 90% of their DNA with us: chimpanzees . Deep in the rainforests of Africa, these primates don't just climb trees or fight over ripe fruit. They also communicate, and they do so with surprising complexity.

They make themselves understood through gestures with almost the same cadence and speed as people. They know how to give each other clues to devise plans for mutual benefit . Like humans, they learn by observing : they imitate what their peers do and integrate it into their daily lives. Science has long focused on these facial expressions, while vocalizations were a less explored aspect. But these peculiar screams and shrieks contain more complex messages than one might think. This is according to an international team of researchers who immersed themselves in the thicket of the dense and humid forest ecosystem of the Ivory Coast (Africa) and recorded more than 4,000 vocalizations of 53 wild chimpanzees ( Pan troglodytes ) affiliated with the Chimpanzee Taï conservation project .

The new analysis of these gasps, grunts, and cries, published in the journal Science Advances, revealed a fascinating finding: chimpanzees combine these sounds into specific vocal sequences to refer to different everyday situations in the wild. They use these calls to search for food, build a nest, confront a threat, or react to aggression. The study, led by Cédric Girard-Buttoz, a researcher at the Center for Neuroscience Research in Lyon (France), identified 16 of these vocal combinations, or bigrams. The authors describe four distinct mechanisms by which meaning is transformed through these combinations. Most importantly, the combination of these vocalizations is not random.

“In essence, what we're seeking is to understand the origin of human language,” the lead author tells EL PAÍS. The research, published this Friday, suggests that these vocal patterns represent an intermediate stage in the evolution of language. “Chimpanzees use individual calls that seem to function as words,” Girard-Buttoz explains. Chimpanzees can't speak because they don't have the appropriate anatomical structure, but they do manage to communicate.

These sound combinations are like tiny building blocks. They're comparable, according to the authors, to when humans combine terms like "cold" and "rainy" in a single sentence to convey an idea. "The vocalizations are the same across all populations, from Senegal to Tanzania, but the combinations do vary slightly," she says. Lara Carrasco, a PhD in Primatology at the University of Barcelona, ​​believes it's important to investigate the origins of language, but acknowledges that it remains a complicated task. "In the end, we tend to anthropomorphize [attribute human qualities] and we apply everything to our own context and way of interpreting it," she notes. For her, it's "complicated to interpret."

This isn't the first time bigrams have been studied. Until now, this phenomenon has only been analyzed in isolation and in different species. Some birds, such as the Sumatran babbler ( Garrulax bicolor ), also combine sounds, but only in dangerous situations. Chimpanzees, on the other hand, demonstrate a flexibility and richness that is more similar to ours. "Their communication is more versatile and diverse than that of other animals," adds Girard-Buttoz.

Primatologist Miquel Llorente , a professor at the University of Girona, believes the study forces us to revisit a line of research that had been "somewhat shelved." "Perhaps it's worth revisiting how chimpanzees use these calls, which can help us better understand how humans have come to communicate the way they do," he says.

Messages in the roots of trees

Gestures and vocalizations aren't their only means of expression. Chimpanzees also communicate with their bodies. They strike hollow roots, branches, and stones with their hands and feet, generating rhythmic sounds that travel through the forest. This drumming isn't random. It has rhythm and purpose.

Another study in the journal Current Biology shows that eastern and western chimpanzees—two distinct subspecies—drum the outer roots of trees with their hands and feet. The research, led by Vesta Eleuteri of the University of Vienna (Austria), analyzed 371 drumming episodes over 24 years and found that chimpanzees don't tap randomly, but rather rhythmically. "Some even do it with isochrony [temporal regularity]," Eleuteri explains.

Those regularly spaced beats the researcher mentions have a percussion similar to the song "We Will Rock You" by the band Queen. And again: those beats follow defined rhythms, they're not random. It's not that chimpanzees make music as humans understand it, but they use rhythm to communicate over distances. This is also something that communities like the Bora , who inhabit both Colombia and Peru, the Akan (in Ghana), and the Bantu (located from Cameroon to Somalia) do.

“Although chimpanzees aren't making music, the skills they use (such as generating rhythmic patterns on objects) could have been evolutionary building blocks for the development of musicality,” he notes. Scientists, on the other hand, observed that western chimpanzees begin drumming before the pant-hoot call. This call has several phases: an introduction, a crescendo, and a climax. “Eastern chimpanzees drum during the final call,” he clarifies.

A window to the past in danger

Studies of chimpanzees and their ancestors began with Jane Goodall's pioneering research in the 1960s, marking a turning point in our understanding of these primates and their place in evolution. All of this leads to a key conclusion: communication is not unique to humans. It's likely that their ancestors already possessed many of the basic elements of complex communication.

Humans, in Cédric Girard-Buttoz's opinion, have taken this system to the highest level. "The difference between animal communication and human language may not be so much one of nature, but of degree," he reflects; but chimpanzee conservation is key to continuing studies on primate communication. These animals are critically endangered due to habitat loss, hunting, the pet trade, and disease. It is estimated that there are approximately 170,000 to 300,000 chimpanzees left in the wild.

"Conservation shouldn't focus solely on numbers, but on preserving their cultural diversity. Each group offers a window into the lives of chimpanzees and our own past as humans," concludes Vesta Eleuteri.