Despite being separated by over 5 million years on our respective evolutionary paths, it appears that nearly 90 percent of the gestures human children use to communicate are shared with those used by chimpanzees. Lacking the capacity for complex verbal speech, the great apes employ a non-verbal language made up of hand and body gestures, whereas humans have well-developed part of the brain called "Broca’s area" that enables us to speak. But before a human child learns to speak a language, they appear to use an ancient gestural language that our ancestors used to communicate with one-another.
The study, conducted by an international team of researchers in Germany, Scotland and Switzerland, studied thirteen children aged between 12 and 24 months; six of the children were from Germany, and seven were from Uganda, with the two different cultures used "to reduce bias from the impact of culture and native language on early gesturing," according to the study paper.
"Wild chimpanzees, gorillas, bonobos and orangutans all use gestures to communicate their day-to-day requests, but until now there was always one ape missing from the picture—us," explains senior study author Catherine Hobaiter, a scientist with the School of Psychology and Neuroscience at the University of St Andrews. "We used exactly the same approach to study young chimpanzees and children, which makes sense—children are just tiny apes."
The study found that the toddlers made 52 distinct gestures, including motions such as arm raising, claps, stomps, hugs, head-shaking, etc. Of these gestures, 46 of them, or 89 percent, overlapped with gestures used by chimpanzees, of whom employ this as a non-verbal language with a vocabulary of roughly 80 gestures. Researchers with the University of St Andrews in Scotland have recently compiled "The Great Ape Dictionary", a compendium of gestures used to help decipher the gestures of chimpanzees, bonobos, gorillas, orangutans, and humans.
The scope of the overlap of gestures between chimpanzees and human children surprised the researchers, according to Hobaiter. "We thought that we might find a few of these gestures—reaching out your palm to ask for something or sticking your hand up in the air—but we were amazed to see so many of the ‘ape’ gestures used by the children."
This finding suggests that, despite the 5-6 million years since chimpanzees and humans split from a common ancestor, a common thread regarding our gestural languages has remained intact. Somewhere along the way, human speech evolved into the complex method of communication that we use today, while our great ape cousins have stuck to gestural languages. But before human infants learn to speak, they appear to default back to our earlier ancestry to communicate with the world.
"This apparently substantial overlap in the repertoire and use of gestures we observed in our sample suggests that before or at the early onset of language proper, human infants’ gestural repertoire is, at some level, largely shared with other apes," according to the paper. So if you’re in the habit of calling your child your "little monkey", you may be more correct than you realize.