In Taï National Park, Côte d’Ivoire, the vocalizations of chimpanzees resonate through the forest, revealing an intricate system of communication. Researchers from France have documented a previously unknown capacity for these primates to combine sounds in flexible ways, akin to how humans construct sentences. This groundbreaking study, published May 9 in Science Advances, could indicate a vital evolutionary step towards the complex syntax found in human language, as it suggests that chimpanzees possess a unique ability to convey diverse meanings through specific sound combinations.
Chimpanzees (Pan troglodytes) were already recognized for their diverse vocal repertoire, which includes approximately a dozen distinct sounds that can be rearranged into various sequences. Researchers, led by Cédric Girard-Buttoz from CNRS in Lyon, explored whether these apes utilized multiple strategies to combine sounds, akin to human linguistic structures. By analyzing recorded vocalizations of 53 adult chimpanzees, the team focused on identifying short sequences called "bigrams"—specific pairs of sounds that could signal different meanings or intentions, revealing an unprecedented complexity in chimp communication.
An extensive audio study conducted over two years involved analyzing over 4,300 chimpanzee vocalizations, culminating in the identification of 16 distinct bigrams, including combinations like a grunt followed by a bark or a panted hoo followed by a scream. Statistical methods helped the researchers correlate these combinations to specific behaviors, demonstrating that chimpanzees do not adhere to a uniform method of sound production. Instead, their communication employs at least four different strategies, a notable discovery that extends beyond previously documented animal vocalizations.
Unlike other nonhuman species, which tend to rely on limited combinations related to specific situations—such as warnings about predators—chimpanzees leverage their vocal capabilities across a wide variety of scenarios. For example, a “hoo + grunt” combination primarily signals feeding or resting, whereas a “grunt + hoo” may pertain to movement or group merging. This breadth in sound usage indicates a deeper layer of communication complexity, suggesting that chimpanzees can articulate multiple messages simultaneously, reflecting higher cognitive functions similar to forming sentences.
The implications of these findings shine a spotlight on an important developmental milestone in the evolution of language. The discovery suggests that chimpanzees possess foundational elements for complex language, presenting a more robust framework for communication than previously understood. Fellow researchers, including Simon Townsend from the University of Zurich, have acknowledged the significance of these findings, noting that while bonobos exhibit similar combinatorial tendencies, chimpanzees employ an even richer set of vocal skills. Evidence shows that a deeper understanding of their sounds could reshape our knowledge of animal communication hierarchies.
Moving forward, researchers are keen to explore whether chimpanzees utilize sentence-like structures in their calls, placing the subject first followed by a verb, and if they can integrate bigrams into longer sequences of sounds. Such investigations hold the promise of unveiling even more complexity in primate communication, potentially redefining the evolutionary lineage of language capabilities. The discovery of sophisticated combinatorial vocal systems in chimpanzees could bridge the gap between animal calls and human languages, offering profound insights into the cognitive evolution that led to linguistic capabilities.
