Research conducted by the Hebrew University of Jerusalem has revealed that marmoset monkeys engage in name-calling behavior, a trait previously observed only in humans, dolphins, and African elephants.

Naming others is considered a sign of highly advanced cognition in social animals, and marmoset monkeys have now joined this exclusive club, according to a new study published in the journal Science on Thursday, August 29th.

These tiny primates use loud, high-pitched calls to assign “vocal labels” to each other, as shown by research from a team at the Hebrew University of Jerusalem.

“We’re very interested in social behavior because we think that’s what essentially made humans so special compared to other animals,” said lead author David Omer. “We don’t run fast, we don’t fly, we don’t excel at anything other than being social, and all of our achievements as a society are our social achievements,” he added.

Marmosets are ideal subjects for studying the evolution of social behavior and language in humans, Omer explained, because they display similar traits and live in small, monogamous family groups of six to eight individuals that raise their offspring cooperatively.

Led by graduate student Guy Oren, the researchers recorded natural conversations between pairs of marmosets separated by a visual barrier, as well as interactions between the monkeys and a computer system that played pre-recorded calls.

They discovered that these animals use “phee calls” (high-pitched vocalizations as loud as power tools) to address each other. Notably, the marmosets could recognize when such calls were directed at them and were more likely to respond when called by name.

Convergent evolution

The ten marmosets used for testing came from three different families, and the research also revealed that members of a family group used the same sound features to encode different names, similar to human dialects or accents. This was true even for adult individuals that were not related by blood, suggesting that they learned from others within the family group.

Marmosets are relatively distant relatives of humans, having last shared a common ancestor about 35 million years ago, while humans and chimpanzees may have split between 5 and 7 million years ago.

Rather than attributing this behavior to genetic proximity, Omer suggests that the marmosets’ acquisition of vocal tags is due to “convergent evolution,” where they developed similar traits in response to comparable environmental challenges.

For these primates, vocal tagging may have been crucial to maintaining social bonds and group cohesion in the dense rainforests of South America, where visibility is often limited.

How and when humans began to speak is still a matter of debate, but until recently, many scientists dismissed the idea that clues could be found in other primates. “We can still learn a lot from nonhuman primates about the evolution of language in humans,” Omer said. He also noted that the analysis of marmoset calls was made possible by recent advances in computing power and machine learning.

Looking ahead, an interesting avenue for future research could be leveraging AI to better decipher the content of these peculiar conversations.