New research suggests wild chimpanzees have developed a far more nuanced communication system than previously realized, using several mechanisms that combine their vocalizations to create new meaning.
These elements of chimpanzee communication, described in a study published Friday in the journal Science Advances, resemble some of the fundamental building blocks of human language.
Scientists analyzed recordings of three groups of chimpanzees living in the Ivory Coast and found that chimps can combine their hoots, grunts and calls in a similar way to how humans use idioms or change the order of words to build new phrases.
The new research is the first time scientists have documented such complexity in a nonhuman communication system, and they think that the chimpanzees’ abilities represent an evolutionary transition point between rudimentary animal communication and human language.
“Generating new or combined meanings by combining words is a hallmark of human language,” Catherine Crockford, a researcher at the Max Planck Institute for Evolutionary Anthropology who co-directs the Tai Chimpanzee Project, said in a news release. “It is crucial to investigate whether a similar capacity exists in our closest living relatives, chimpanzees and bonobos.”
A separate study, published last month, provided similar evidence that bonobos, another primate, can also combine their calls to modify calls and form phrases. Together, these studies suggest both species evolved to develop fundamental building blocks of human language.
Bonobos and chimpanzees are the species most closely related to humans in evolutionary history, which means all three species could have evolved from a common ancestor with this ability, a theory that could help researchers understand how human language developed.
“Our findings suggest a highly generative vocal communication system, unprecedented in the animal kingdom, which echoes recent findings in bonobos suggesting that complex combinatorial capacities were already present in the common ancestor of humans and these two great ape species,” Cédric Girard-Buttoz, a researcher with the ENES bioacoustics research lab and the first author of the study, said in a news release.
The researchers discovered these new complexities in chimpanzees’ vocal system by following particular animals in the field from dawn to dusk for about 12 hours each day, recording the sounds the chimpanzees made and the responses from others in the group. They recorded more than 4,300 vocalizations from 53 wild chimpanzees.
During the chimps’ vocal calls, the researchers also tracked what activities, social interactions and environmental changes were occurring, and noted if the animals were eating, playing or encountering a predator, for example.
Then, the researchers performed a statistical analysis of specific two-call combinations — such as a grunt followed by a bark — that were documented in multiple animals.
The researchers found that chimpanzees combined calls in all of their daily aspects of life and that the combinations could express a wide variety of meanings.
Simon Townsend, a professor at the University of Zurich who studies cognition in primates and contributed to the bonobo research but was not involved in this study, said the paper is the first to show chimpanzees using several different mechanisms that are considered to be among the building blocks of language.
He said the evidence does suggest that the common evolutionary ancestor of bonobos, humans and chimpanzees probably had this ability, too.
“It does seem to suggest that our linguistic abilities were already well on the way to evolving … 6-7 million years ago,” Townsend said, referring to when the species likely branched off from one another in the evolutionary tree.
Not all primates show evidence of such complicated communication. Forest monkeys, which have relatively simple social groups, mostly use vocalizations to manage predatory threats, Townsend said.
But he thinks the formation of increasingly large and complicated social groups — an element common to great ape species and humans — likely spurred the evolution of more complex communication and eventually the ability to form language.
For bonobos and chimpanzees, “the biggest challenge for them is navigating their complex social world. They live in much larger groups. … There’s aggression, there’s reconciliation, there’s territoriality, there’s intergroup interactions, and vocalizations, I think, is one evolutionary solution to trying to manage these complex and fine-grained social interactions,” Townsend said.
In human language, syntax is the set of rules that creates a system capable of expressing an infinite number of meanings.
“Syntax is all about providing more and more precise, refined information. And you probably only need to do that when your social interactions get more complex,” Townsend said.
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