Mirroring Mothers 

Communication is more than just words – it encompasses gestures, postures, and facial expressions, and consists of both verbal and non-verbal symbolism. 

While in constant use by humans and animals, its origins remain somewhat mysterious. 

“It’s not like the emergence of communication is visible in the fossil record,” Joseph G. Mine, author of a new study tracing the origins of communication, told NPR. “There’s this big kind of open question of – how did human language evolve? How did humans or hominins communicate millions of years ago?”  

The study focused on chimpanzees, one of humans’ closest relatives, suggesting that any traits humans share with chimps today could date back to when our lineages diverged, between six to eight million years ago. 

Researchers observed about 22 wild chimps (Pan troglodytes) in a tropical rainforest that is part of Kibale National Park in Uganda, where they could film their natural behavior. 

Back in the lab, the team analyzed hundreds of hours of footage, looking at vocal signs –grunts, barks, and whimpers – and nonvocal communication – arm movements, gaze direction, and body postures – to identify which behaviors tended to occur together more often than expected and couldn’t be attributed to chance. 

“So they might combine a pant hoot vocalization with running, but also with slapping the ground or grabbing a branch,” said Mine. 

The team had already published a repertoire of 108 combinations last year. 

Now, by studying chimps older than 10, they found that their communication style closely resembled that of their mothers’ and maternal relatives but showed little similarity to that of their fathers or paternal relatives. 

“What we see is that certain chimpanzee mothers tend to produce many vocal-visual combinations, while others produce few,” Mine said in a statement. “And the offspring end up behaving like the mothers, resulting in family-specific tendencies.” 

Chimp mothers are the primary caregivers – fathers don’t contribute to parenting – indicating that there might be a learned component in chimps’ communication techniques. 

“The mother is really the valid social template that they can be learning from, but they don’t really have the exposure that would allow them to learn from their fathers,” explained Mine. 

The fact that communication styles in chimps older than 10 still mirrored their mothers’ indicates the lasting impact of maternal kin influences: That is the age at which chimps begin gaining independence from their primary caregivers. 

These results, researchers say, suggest that the social learning of communication evolved earlier than previously believed.