BURSTHumans are not the only species to combine concepts to build more complex meaning, a new study found.
Bonobo chimpanzees combine calls in a manner similar to how humans structure words to make phrases and sentences, according to findings published on Thursday in the journal Science.
The pygmy chimpanzees “seem to combine calls to convey meaning that cannot be conveyed through single calls alone,” the researchers wrote.
Because the genetic lines of humans and bonobos diverged more than 7 million years ago, the research suggests the roots of complex language go far deeper than had been previously believed.
It follows other surprising findings of humanlike behavior in apes and monkeys, like the previous findings that uncovered the building blocks of human language in chimpanzee calls; strong similarities between basic jokes in humans and other primates; and monkeys using simple stone tools.
Thursday’s findings also suggest that the ability to combine sounds in “complex ways is not as unique to humans as we once thought,” Mélissa Berthet, an evolutionary anthropologist at the University of Zurich, said in a statement.
To arrive at this finding, Berthet and other researchers first built a comprehensive ‘dictionary’ of bonobo calls.
That achievement marked “the first time that we have determined the meaning of calls across the whole vocal repertoire of an animal,” Berthet added.
This allowed the scientists to study whether bonobo communication — the use of words like "grammar" or "language" is controversial when applied to non-human species — had a key feature of human language: an ability to create meaning from smaller components that is greater than the sum of its parts.
In its most "trivial" form, that looks like a compound word, where the concepts are independent of each other and combine to make a short list: a “French cheese” is both cheese and French; a “tall man” is both tall and a man, and neither quality influences the other.
But in more complicated forms, the meaning is greater than the sum of their parts. For example, a “cold war” is neither cold nor a war, but something more complex.
The concept had never been found in nonhuman species — until now. Researchers unveiled distinct vocalizations could combine to create greater meaning than either alone. A high-pitched hoot, for example, seems to mean, “Pay attention to me,” while a low-pitched one signifies, “I am excited or worried.”
Put together — often by a speaker facing another bonobo who is threatening them — high or low hoot combination seems to mean something like “Come help quick!”
Similarly, the attention-seeking high hoot can combine with a high-pitched yelp — “Join me over here!” — to convey that a party of bonobos is about to set off for travel.
The researchers also note that communication in great apes may be even more complex, because different call combinations are also often happening in context of different gestures — another key component of communication in primates and humans alike.