Hoots and grunts from bonobos show signs of complex communication, researchers say

A recent study reveals that bonobos, a species of great ape inhabiting African rainforests, utilize their vocalizations—including peeps, hoots, and grunts—to express sophisticated thoughts in patterns reminiscent of human language structures. This groundbreaking research sheds light on the complex communication abilities of these primates.

The research indicates that bonobos, our closest living genetic relatives, possess the capacity to combine various call types to form sequences where one vocalization alters the meaning of another. Researchers state that this marks the first clear documentation of such behavior in the animal kingdom.

Published in the journal Science, the study challenges the long-held view that humans are the only species capable of ‘nontrivial compositionality’—the ability considered a cornerstone of human language. This finding suggests that the building blocks of complex communication are not exclusive to humans.

“While we wouldn’t assert that bonobos possess language in the human sense, as language is uniquely human,” explained Simon Townsend, a cognition professor at the University of Zurich and a study author, “our findings demonstrate that elements of language are evident in the communication system of bonobos.”

External experts have affirmed the study’s compelling nature. They suggest that given the shared ancestry between humans and bonobos, this research could provide insights into the evolutionary origins of human language capabilities.

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Robert Seyfarth, professor emeritus at the University of Pennsylvania, specializing in primates and cognition and uninvolved in the current study, praised it as “a terrifically novel and creative study.” He elaborated, “The evolutionary origins of language are akin to bipedalism—it’s a gradual process with intermediate stages. This research helps us refine our understanding of how this evolutionary trajectory began.”

It remains plausible that other species, such as chimpanzees, might also exhibit the capacity to form phrases where vocalizations modify each other’s meaning, but more research is needed in this area.

Townsend noted, “Bonobos may surpass chimpanzees in this ability, they might perform similarly, or numerous other species could share this trait. Crucially, we now possess a methodology to investigate these possibilities.”

Deciphering Bonobo Communication: The Eavesdropping Method

This significant discovery was the culmination of months spent traversing rainforests and tracking wild bonobos while recording their vocalizations using microphones.

Mélissa Berthet, the lead author of the study from the University of Zurich, dedicated approximately six months in the Democratic Republic of Congo alongside colleagues at the Kokolopori Bonobo Reserve, observing three groups of wild bonobos. Berthet and her team meticulously documented the context surrounding bonobo vocalizations, amassing around 400 hours of audio recordings.

Berthet detailed her methodology: “I utilized a checklist of approximately 300 contextual parameters. This included factors such as whether the bonobo vocalizing was feeding, resting, or grooming.”

Given the complex, matriarchal social structures of bonobos characterized by considerable movement and activity, Berthet maintained meticulous records of group dynamics to understand the broader social context influencing communication.

The researchers meticulously cataloged over 700 vocal calls, including combined calls, along with the specific situations in which they were used. Subsequent analysis of the relationships between these data points revealed at least four instances where bonobos combined distinct vocalizations to generate novel meanings.

While the precise meaning of each bonobo call remains under investigation, the researchers were able to infer their likely purpose based on observed contextual cues.

According to the researchers, certain calls appeared to convey meanings such as “I’m feeding,” “Let’s build a nest,” or “Let’s continue traveling.”

Bonobo group sizes frequently fluctuate as individuals join and leave.

Berthet elaborated, “Their communication primarily revolves around group coordination. Similar to humans navigating family, work, and social circles, bonobos require sophisticated communication for group coordination. It’s therefore logical that much of their communication is focused on this essential aspect of their social existence.”

Bonobos and the Evolutionary Roots of Language

As the closest genetic relatives to humans, bonobos and chimpanzees provide crucial insights into our shared evolutionary history. This research suggests that the last common ancestor of these species, believed to have existed between 7 and 13 million years ago, may have possessed the rudimentary communication skills observed in modern bonobos.

The study’s authors suggest that bonobos effectively serve as a window into humanity’s evolutionary past.

This research prompts further inquiry into the evolutionary pressures that propelled ancient humans to develop more complex forms of verbal communication.

Sara Skiba, a research scientist and communications director at the Ape Initiative, a bonobo research facility, commented, “If bonobos and chimpanzees inherently possess these foundational elements within their communication systems, it can illuminate the critical juncture at which human language evolved towards greater complexity.” Skiba was not part of this study.

Studying bonobos in their natural habitat presents considerable challenges. They inhabit fragmented regions of the Congo, an area impacted by recent human conflict.

Martin Surbeck, an author of the study and assistant professor of human evolutionary biology at Harvard University, noted that the species is endangered, with a population likely under 20,000 individuals.

Surbeck emphasized, “Bonobos offer a unique opportunity to reflect on humankind. They allow us to understand ourselves in ways otherwise unattainable. Their loss would signify the loss of a significant aspect of our heritage.”