JUANA SUMMERS, HOST:
Our ability to communicate using words and gestures - how far back does that go? A new study involving chimpanzees suggests it goes back millions of years. Here's science reporter Ari Daniel.
ARI DANIEL, BYLINE: As I talk to you right now, I'm moving my hands, adjusting my posture and facial expressions. You do it too. Human communication is a complex weave of verbal and nonverbal signals.
JOSEPH MINE: Yeah, that's right - in a kind of very rich and combined way.
DANIEL: But how and when this capacity originated is somewhat mysterious, says Joseph Mine, currently a biologist at the University of Rennes in France. It's not like the emergence of communication is visible in the fossil record.
MINE: There's this big kind of open question of - how did human language evolve? How did humans or hominins communicate millions of years ago?
DANIEL: Mine is trying to answer that question by looking to one of our closest relatives - chimpanzees. The idea being, whatever traits we share with chimps today could go back to at least when our ancestors split off from one another, 6- to 8 million years ago.
(SOUNDBITE OF INSECTS CHIRPING)
DANIEL: Mine did his fieldwork here, in Kibale National Park in Uganda.
MINE: A beautiful tropical rainforest where, you know, these chimpanzees live in the wild, and therefore we can observe their natural behavior - this community of approximately 60 individuals.
(SOUNDBITE OF FOOTSTEPS CRUNCHING)
DANIEL: Over many months, Mine and his colleagues followed the animals to film and audio record them, which is what you've been hearing.
Back in the lab, he pored over hundreds of hours of footage. He searched for any vocal and nonvocal behaviors...
MINE: So, you know, facial expressions, gestures and body posture, and were they walking or standing or sitting?
DANIEL: ...That were produced in tandem more often than expected by chance.
MINE: So they might combine a pant hoot vocalization with running, but also with slapping the ground or grabbing a branch.
(SOUNDBITE OF CHIMPANZEE SCREECHING)
DANIEL: In work published last fall, Mine identified a repertoire of 108 such combinations, but then he dug deeper. And when he examined chimps 10 years and up, he found that individuals related through their mother produce similar amounts of these combinations. On the paternal side, though, there was no such pattern. That is...
MINE: If your mother tends to gesticulate a lot while vocalizing, then you're also likely to do so. But if that's the case for your father, then you won't necessarily show this kind of resemblance.
DANIEL: A chimp spends most of its early years with its mom, not its dad, so Mine concludes that these verbal-nonverbal combos are most likely learned rather than inherited.
MINE: 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.
DANIEL: Young humans also learn to communicate from those they spend the most time with, meaning this ability may well date back at least to our last common ancestor with chimps.
MINE: This fact that we acquire parts of our communication socially seems to be potentially a very ancient trait, a feature of our lineage for several million years.
DANIEL: The results are published in the journal PLOS Biology. Cat Hobaiter is a primatologist at the University of St. Andrews who wasn't involved in the research.
CAT HOBAITER: My bet is that we would see something similar in gorillas and orangutans. Then we're talking about something that might be 16-, 17 million years old. So long before humans were human, apes were learning socially from each other.
DANIEL: Hobaiter says future work could try to decode these combinations to figure out what they might mean. For NPR News, I'm Ari Daniel.
(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.
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