Millions-Year-Old Roots of Human Communication Revealed in Chimpanzee Study

The intricate tapestry of human communication encompasses a blend of verbal and nonverbal cues, a complex interplay of vocal and visual signals.

Biologist Joseph Mine, from the University of Rennes in France, posits that this multifaceted method of communication evolved over time, but the exact origin remains elusive. Unlike the fossil record’s vivid depiction of our physical ancestors, there are no preserved gestures or etched syllables from prehistoric times.

“The enigma surrounding the evolution of human language is vast,” says Mine. “We grapple with understanding how humans or hominins communicated hundreds of thousands of years ago, even millions of years ago.”

In an effort to unravel this mystery, Mine focuses on our closest living relatives – chimpanzees. By studying shared traits between humans and chimps, he aims to trace their origins back to the point where the two species diverged around six to eight million years ago.

A study published in PLOS Biology reveals that young chimps primarily learn vocal and visual communication patterns from their mothers and maternal relatives. This mirrors the way human children learn from primary caregivers, leading researchers to speculate that this ability dates back at least that far.

Mine conducted his research with a community of approximately 60 chimpanzees residing in Kibale National Park’s lush tropical rainforest in western Uganda. The animals form subgroups, which frequently split and rejoin; however, these groups typically include at least one mother and her offspring.

Over many months, Mine and his team observed the chimps from a safe distance, filming and recording their vocalizations and physical behaviors. Back in the lab, he analyzed hundreds of hours of footage to identify any combination of vocal and non-vocal cues (such as facial expressions, gestures, gaze orientation, body posture, and movements) that appeared together more frequently than expected by chance.

Mine discovered a repertoire of 108 such combinations during his analysis. It was then he noticed an interesting pattern – chimps from the same family tended to exhibit similar numbers of these vocal-visual combinations.

This finding led Mine to delve deeper into the topic. When he examined chimpanzees aged ten years and older, he found that individuals related through their mother produced similar amounts of these vocal and visual combinations. On the contrary, there was no such pattern among paternal relatives.

Mine surmises that this indicates a learned rather than inherited origin for these vocal-visual combos since, if genetics played a role, the chimps would resemble both parents equally.

“Chimps spend most of their early years with their mothers, not their fathers,” explains Mine. “This suggests that they learn these behaviors from their primary caregiver, who becomes their social template.”

Once learned, it appears these behaviors persist. Young humans also acquire communication skills from the individuals they interact with most frequently, indicating that this ability could extend back at least to our last common ancestor with chimps.

“The fact that we learn parts of our communication socially seems to be an ancient trait – a feature of our lineage for several million years,” says Mine.

Cat Hobaiter, a primatologist from the University of St. Andrews in Scotland, who did not participate in the research, praises the findings as another example of how the social environment shapes primate communication.

“We’re seeing similarities across ape species,” says Hobaiter. “I suspect we would find something similar in gorillas and orangutans. Then we’re talking about something potentially 16-17 million years old – well before humans were human, apes were learning socially from each other.”

Hobaiter suggests future research could aim to decode these combinations to discern their meaning and whether they are specific to this group of animals or shared by all chimpanzees.