In Taï National Park in Cȏte d’Ivoire, a cacophony of chimpanzee vocalizations—grunts, barks, screams, and pants—fills the air. According to a study published in Science Advances on May 9, researchers have discovered that these chimpanzees combine these distinct calls in a manner akin to linguistic building blocks, enabling them to communicate complex meanings. This ability to combine and rearrange pairs of sounds to express different ideas or meanings appears unique among nonhuman animals. Researchers believe this system could represent a crucial evolutionary step between the vocal communication methods of other animals and the syntactic rules that govern human language.
According to Cédric Girard-Buttoz, an evolutionary biologist at CNRS, the defining characteristic of human language lies in our ability to string together sounds into words and subsequently arrange these words into sentences, a feature that distinguishes us from other animals. While chimpanzees possess a complex vocal range, producing around twelve individual sounds that can be arranged into hundreds of sequences, it remained uncertain whether their sound combinations, like those in human language, were employed to create diverse meanings.
To investigate this, Girard-Buttoz and his team recorded vocalizations from 53 adult chimpanzees in the Taï forest during 2019 and 2020. Their analysis of over 4,300 sounds identified 16 distinct “bigrams,” which are short sequences of two sounds, such as a grunt followed by a bark. Through statistical analysis, the researchers linked these bigrams to specific behaviors, thereby uncovering some of their intended meanings.
Chimpanzees, unlike other animals, exhibit a diverse range of sound combination strategies, demonstrating at least four distinct methods previously unseen outside of humans. One strategy involves creating a new meaning (C) by combining sounds A and B. Sound meaning can also be altered by the addition of another sound, similar to prefixes or suffixes in human language. Furthermore, the order of sounds matters; for example, a “hoo + grunt” is generally linked to feeding or resting, whereas a “grunt + hoo” is more often used during travel or when chimpanzee groups merge.
Earlier studies on the evolution of language in animals have shown that species typically exhibit a limited capacity for combining sounds to enhance communication, often relying on a single strategy. These sound combinations are typically used in response to specific events, such as encountering a predator. Because these situations are often dangerous, alarm signals must be precise.
According to Girard-Buttoz, chimpanzees appear to use sound combinations in a broader range of everyday situations. She notes that these combinations might communicate several things simultaneously, similar to how humans use sentences.
The research indicates that chimpanzees possess the ability to communicate complex and nuanced messages, exceeding the capacity of a basic communication system. As an illustration, the combination of “hoo” and “pant” appears to have a very specific meaning, potentially indicating the construction of a tree nest for protection from predators rather than resting on the ground.
Simon Townsend, an evolutionary anthropologist at the University of Zurich unaffiliated with the study, describes it as “a super exciting advance of the field,” emphasizing that “the chimp combinatorial vocal system is more complex than we previously thought.”
Townsend and his team, in a study published in Science earlier this year, employed a similar methodology to analyze communication in bonobos, chimpanzees’ close relatives, demonstrating how one call can modify the meaning of another when combined. According to Townsend, chimpanzees exhibit an even greater level of sophistication with a wider range of communicative strategies.
Girard-Buttoz notes that chimpanzee vocal communication has been studied more extensively than that of bonobos, resulting in a larger dataset and a more comprehensive understanding of the meanings behind their vocalizations.
Here are the rewritten sentences, aiming for clarity and conciseness:
- Girard-Buttoz suspects that bonobos might possess similar communication systems.
- According to Girard-Buttoz, these apes exhibit the foundational elements necessary for complex language. This sound combination “exploded” in humans, giving rise to the vast array of meanings we can convey.
- Girard-Buttoz and his team are currently investigating whether chimpanzees arrange their calls in a sentence-like manner, perhaps with a subject-verb structure. They are also examining whether the apes integrate bigrams into longer sequences of three or four sounds.
C. Girard-Buttoz et al. Versatile use of chimpanzee call combinations promotes meaning expansion. Science Advances. Published online May 9, 2025. doi: 10.1126/sciadv.adq2879. / Berthet, M. Surbeck and S.W. Townsend. Extensive compositionality in the vocal system of bonobos. Science. Vol. 388, April 3, 2025, p. 104.doi: 10.1126/science.adv1170.
