Baby Chimpanzees Develop Distinct Regional Accents, Study Finds

What Baby Chimp Grunts Reveal About the Roots of Human Speech

Two babies born on opposite sides of the world can end up babbling in noticeably different ways by the time they’re toddlers, one shaped by English, the other by Mandarin. Scientists have documented this in humans for decades. New research suggests something remarkably similar happens in chimpanzees, our closest living relatives, and it starts early in life.

A team of researchers studied young chimpanzees at two very different locations, an orphanage in Zambia and a national park in Tanzania, and found that infant chimps already produce grunts and laughs that sound different depending on where they live. As the chimps grew into their juvenile years, their vocal “accents” became sharper and easier to tell apart across every kind of call. That pattern mirrors how human speech develops, and it raises questions about where these differences come from: genes, environment, or the social world around a growing chimp.

This adds real weight to a long-running debate over why chimpanzee populations sound different. Some researchers argue it comes down to biology, while others think it’s shaped by social learning or environment, similar to how a person picks up a regional accent. Tracking how vocal differences unfold over time, this study offers evidence that social and environmental influences may help shape those differences alongside possible genetic effects.

Infant Chimps Already Sound Different, Depending Where They Live

Researchers focused on 30 young chimpanzees, split between infants and juveniles, at Chimfunshi Wildlife Orphanage in Zambia and Gombe National Park in Tanzania. The study, published in the journal PLOS One, compared Chimfunshi’s chimps, in open woodland, with Gombe’s, wild in dense rainforest. Twenty-one of the animals studied were infants, four years old or younger, and ten were juveniles, between four and ten, with one chimp appearing in both age groups as it grew.

Microphones near the animals captured an enormous amount of sound as the chimps went about their day. Just over 4,700 laughs, roughly 3,700 grunts, and close to 2,800 whimpers were recorded, adding up to more than 11,000 calls.

Once recordings were in hand, researchers measured specific sound features of each call, like pitch and rhythm, then fed that data into a computer program built to guess which location a chimp came from based on sound alone. They also made sure no single chatty chimp was skewing results, so what they were really testing for was a signature shared by an entire population, essentially a dialect.

Chimp Accents Sharpen From Infancy Into the Juvenile Years

Results left little doubt. Calls could be sorted by location far more accurately than chance would allow, with whimpers matched to their home site nearly 98% of the time overall, laughs almost 97% of the time, and grunts close to 90% of the time.

Breaking the data down by age told a more layered story. Among infants, grunts and laughs showed clear location-based patterns, but infant whimpers didn’t; the youngest chimps already sounded different when laughing and grunting, but their distress calls sounded pretty much the same no matter where they were raised.

That changed by the juvenile years. By then, whimpers also carried a location-based signature, and every call type got easier to place: grunts went from about 76% accurate in infancy to about 92% by the juvenile stage, laughs from about 93% to nearly 97%, and whimpers from about 77% to almost 85%.

Distress Calls Stay Consistent While Laughs and Grunts Diverge

Researchers offer a reasonable explanation for why whimpers behaved differently in infancy. Whimpers are distress calls, mostly directed at mothers, and if a baby’s cry for help sounded wildly different depending on random genetic quirks, that could make it harder for mothers to recognize and respond. That kind of pressure could keep distress calls consistent across populations early on.

Laughs and grunts may face different pressures. Laughing mostly happens during play with other young chimps, and grunts increasingly get directed toward specific individuals as chimps age, particularly higher-ranking group members. Both situations create repeated chances for social exposure, and potentially, for vocal habits to be shaped by the group around a growing chimp.

Habitat might matter too, the authors note. Gombe’s dense rainforest and Chimfunshi’s open woodland carry sound differently, and other primates, like baboons, adjust calls depending on whether they live in dense or open terrain.

Researchers also considered a simpler explanation: that recording equipment, which differed between sites, might be driving the result. But equipment differences should show up evenly across call types and ages, they argue, and the pattern instead was selective, which doesn’t line up with a technical glitch.

Chimpanzee Accents Point to Deep Roots for Human Vocal Flexibility

None of this proves genetics play no role. There is no migration between the two populations, so researchers say they likely differ genetically to some degree. But the fact that not all calls showed location-based differences in infancy, and that differences grew stronger with age, points toward learning and social environment as forces at work too, not biology alone.

That matters for understanding where human vocal flexibility came from. Humans stand out for how dramatically speech varies across cultures, and this pattern hints that some foundations of that flexibility may reach further back into the evolutionary tree than scientists thought. Chimpanzees, at least, appear to develop increasingly recognizable regional vocal signatures as they grow.

---