Bonobos, the intriguing great apes closely related to humans and chimpanzees, inhabit the lush forests of the Republic of Congo. These fascinating creatures communicate using a variety of vocalizations, including peeps, hoots, yelps, grunts, and whistles. Recent research led by Swiss scientists, particularly Melissa Berthet, an evolutionary anthropologist from the University of Zurich, has revealed that bonobos can combine these basic sounds into more complex semantic structures. This groundbreaking discovery challenges the long-held belief that such linguistic traits were exclusively human.
To delve deeper into bonobo communication, Berthet and her team compiled an extensive database of 700 bonobo calls. They utilized methodologies from distributional semantics, a technique often employed in the reconstruction of ancient languages like Etruscan and Rongorongo. This innovative approach allowed researchers to gain unprecedented insights into what bonobos communicate when they vocalize in their natural habitat.
The core principle of distributional semantics posits that words appearing in similar contexts usually carry similar meanings. To decode an unknown language, researchers must collect a significant corpus of words and convert them into vectors—mathematical representations that help situate them within a multidimensional semantic space. Context data is also crucial, as it provides insights into the situations surrounding the use of these words, which is similarly vectorized.
When Berthet and her colleagues sought to apply this technique to bonobo calls, they faced numerous challenges. “We worked at a camp in the forest, getting up at 3:30 in the morning and walking for one or two hours to reach the bonobos’ nest. Once they woke up, I’d switch my microphone on to record vocalizations throughout the day,” Berthet explained. Each call recorded required meticulous annotation, with a long list of contextual parameters needing to be answered for every call. The research team had to respond to 300 specific questions regarding each of the 700 recorded calls.
Initially, Berthet focused on determining the meanings of the basic calls, such as singular grunts and yelps. The analysis revealed that grunts were frequently used in contexts like grooming, feeding, or moving, and were interpreted as a way to attract attention—similar to saying, “look at me.” Yelps were identified as imperatives meaning “let’s do this,” while peeps suggested a more tentative invitation, akin to “I would like to…”
Additionally, low hoots were translated as “I am excited,” while high hoots signaled the caller's presence in potentially dangerous situations. Whistles conveyed a message of “let’s stay together.” After establishing the meanings of these basic calls, the research team explored how bonobos combined them to form more complex messages.
Interestingly, bonobos combined yelps and grunts into a simple compositional structure that conveyed “let’s do what I do,” particularly evident during the construction of night nests. However, Berthet’s team uncovered instances of non-trivial compositionality, marking the first discovery of such a phenomenon outside of human communication. One notable combination was the high hoot and low hoot, which functioned as a distress call while also serving to interrupt displays of dominance among other bonobos.
Another significant combination involved either peep or yelp paired with a high hoot, used to coordinate movements before traveling. Lastly, the combination of “I would like to” peep followed by “let’s stay together” whistle indicated romantic intentions, highlighting the complexity of bonobo social interactions.
While Berthet's team made substantial progress, they acknowledged that their analysis might be too simplistic. “There may be subtle acoustic differences that could lead to different meanings, and it may be our dictionary is too rough,” she noted. Furthermore, the study did not include the gestures that bonobos often use alongside their vocalizations, which could further refine or alter the meanings of their calls.
Berthet envisions applying the same methodology to explore more about animal communication, extending her research to other species, including chimpanzees, gibbons, gorillas, and monkeys. “Our goal is to trace when abilities like non-trivial compositionality emerged in primate evolution,” she stated. The findings could significantly enhance our understanding of communication across various species, shedding light on the evolution of language and social interaction in the animal kingdom.
In conclusion, the research on bonobos not only enriches our understanding of animal communication but also opens doors for future studies that could reveal the intricate dynamics of social interactions in the animal world. With continued exploration, we may uncover even more about the fascinating ways in which these great apes express themselves.
