(Photo : Wikimedia Commons/Delphine Bruyere)
Communicative gestures used by human infants, baby chimpanzees, and baby bonobos are all incredibly similar, asserts a new study, which also claims humans inherited gestures from a 6-million-year-old shared ancestor.
"The similarity in the form and function of the gestures in a human infant, a baby chimpanzee and a baby bonobo was remarkable," said Patricia Greenfield, co-author of the study published in the journal Frontiers in Pyschology.
Chimpanzees and bonobos (formerly known as pygmy chimpanzees) are the closest known relatives to humans in the animal kingdom. The study shows that gestures baby humans, chimps, and bonobos were all "predominantly communicative," according to Greenfield, and the same. For instance, all three exhibited pointing, and raising their arms to big picked up.
The team observed an 11-month-old female human infant until she was 18 months old, and 12-month-old apes until they were 26 months old. All three demonstrated the same pathway when developing their language skills. It was always gestures first, and then symbols, represented by words for the child and lexigrams for the apes. The human infant quickly outpaced the apes in the second half of the study, when symbols were introduced.
"This was the first indication of a distinctive human pathway to language," Greenfield said. "This finding suggests that the ability to combine gesture and vocalization may have been important for the evolution of language."
Through the study the researchers concluded that the similarities in gesture development indicate that the form of communication descended from a common ancestor between the three. The current fossil records points to an ancestor that lived 6 million years ago, whose evolutionary offspring eventually split into the humans, chimpanzees, and bonobos we see today.
"Our cross-species comparison provides insights into the communicative potential of our common ancestor," lead author lead author, Kristen Gillespie-Lynch said.