Researchers have uncovered that bonobos, the great apes inhabiting the Republic of Congo and closely related to humans and chimpanzees, possess a rich form of communication consisting of various vocalizations such as peeps, hoots, yelps, grunts, and whistles. A team from the University of Zurich, led by evolutionary anthropologist Melissa Berthet, has found that these apes can combine these basic sounds to convey more complex meanings, exhibiting a form of communication known as non-trivial compositionality—a concept previously believed to be exclusive to humans.
Berthet and her team compiled an extensive database of 700 distinct bonobo calls and analyzed this data through distributional semantics, a methodology typically used to reconstruct ancient languages such as Etruscan and Rongorongo. This research offers a rare window into the meanings behind bonobo vocalizations in their natural habitat.
Understanding Through Context
At the heart of distributional semantics lies the principle that words used in similar contexts often share analogous meanings. To elucidate an unknown language, researchers must gather a significant corpus of words and translate them into vectors—mathematical entities that situate these words within a multidimensional semantic landscape. Contextual data, which outlines the situations in which these words are utilized, is equally important and is also vectorized. When these vectors are mapped together, words with similar meanings typically cluster in proximity. Berthet and her colleagues set out to apply this technique to the vocalizations of bonobos. However, the implementation proved to be challenging.
“Our team operated from a camp deep in the forest, beginning our days at 3:30 AM to trek one to two hours to the bonobos’ nests. As they awoke, I would activate my microphone and record their vocalizations throughout the day,” Berthet recounted. Each recorded sound required thorough annotation based on an extensive set of contextual parameters. Berthet utilized a comprehensive questionnaire addressing queries such as whether other groups were nearby, the presence of predators, and the social behaviors of the caller, including feeding, resting, or grooming. In total, 300 questions were essential to ascertain for each of the 700 calls recorded.
