‘Baby Talk’ Could Be The Reason Humans Are The Only Speaking Species On Earth

ZURICH — To outsiders, parents using “baby talk” may seem like they’ve lost their minds. We spend endless hours having one-sided conversations with tiny humans who can’t even hold up their own heads. But a new international study reveals this seemingly ridiculous behavior might be the secret sauce that separates us from every other species on the planet.

The study, published in Science Advances, shows that human infants receive a staggering 399 times more direct vocal communication than baby bonobos, and 69 times more than baby chimpanzees. This research, which compared vocal interactions across all great ape species, suggests that our uniquely chatty parenting style may have been crucial in the evolution of human language.

Research teams followed infant great apes through dense forests in Central Africa, Indonesia, and Uganda, using directional microphones to capture every vocalization within earshot. For human infants, they analyzed hours of naturalistic recordings from families in their everyday environments.

Researchers examined vocal communication patterns in human infants from communities in Peru, Papua New Guinea, Nepal, and Switzerland. They did this alongside wild populations of all nonhuman great apes: bonobos, chimpanzees, gorillas, and orangutans. They followed infants aged 10 to 60 months, carefully documenting every instance of directed versus background vocal communication.

Researchers defined “directed” communication as vocalizations in which the caller’s head was oriented toward the infant and the call led to some kind of response, like the baby looking up or changing behavior. Background communication included all the chatter that happened around the infant but wasn’t specifically aimed at them.

Sample sizes included 68 human infants across four cultures, 17 chimpanzee infants from Uganda, 8 bonobo infants from the Democratic Republic of Congo, 6 gorilla infants from the Central African Republic, and 11 orangutan infants from Indonesia.

Baby Talk Across Species

Human caregivers spent about 95% of their vocal time directly addressing their infants, while great ape mothers directed vocalizations at their babies less than 1% of the time. Even when accounting for the fact that some species are naturally more vocal than others, the difference remained clear.

Orangutan babies received the least direct communication of all species studied. This makes sense since orangutans are largely solitary creatures, with mothers and infants spending most of their time alone in the forest canopy. Chimpanzees showed the highest rates of direct communication among the great apes, though still far below human levels.

Even cultures known for less direct infant interaction showed vastly higher rates of infant-directed communication than great apes. The pattern held across all four human cultures studied, from the Amazon rainforest to the Swiss Alps.

When researchers looked at background vocal communication, conversations happening around infants but not directed at them, the numbers were much more similar across species. Human infants and baby chimpanzees experienced roughly equivalent amounts of this surrounding chatter. Baby bonobos actually heard slightly more background communication than human infants.

Early human ancestors probably relied heavily on overhearing conversations to learn communication skills, much like modern great apes do today. The expansion of direct, infant-focused communication in humans appears to be a more recent evolutionary development.

Direct baby talk has long been considered good for language development, but some cultures rely more heavily on children learning by listening to conversations around them. Yet all human cultures in the study showed higher rates of infant-directed speech compared to any great ape species.

Human Language Evolution

Other vocal learning animals also show evidence of modified communication when interacting with their young. Bottlenose dolphin mothers adjust their signature whistles when their calves are present, and greater sac-winged bats change the pitch and tone of their calls when addressing pups.

Talking directly to babies could be a special trait of species that have to learn how to make their sounds, instead of just being born knowing them. Unlike great apes, who mostly rely on instinct for their calls, humans need tons of practice to learn language, and all that baby talk gives them exactly the right kind of help.

As babies get older, parents in all species tend to talk to them more. Even ape moms seem to notice when their little ones are ready to interact more. But even with this increase, the amount of communication apes do with their babies is still tiny compared to how much humans chatter with theirs.

As our ancestors started depending more on learning to communicate instead of just using instinct, parents who talked a lot to their babies gave their kids an advantage in picking up language skills. Over time, it looks like our species actually evolved to need and benefit from all that early baby talk.