Chimps communicate by smiling like humans, share common ancestor
Their study shows chimps and humans have even closer evolutionary ties than was previously believed.
The university further found that, like humans, chimpanzees can create ‘silent smiles’ without a laughing sound.
Scientists filmed 46 chimps at the Chimfunshi Wildlife Orphanage in Zambia, where cameras tracked the primates’ facial expressions. Their movements were analyzed by a facial coding system called ChimpFACS.
Dr Marina Davila-Ross, from the University’s Centre for Comparative and Evolutionary Psychology, said the ‘silent smile’ trait allowed humans and chimps to communicate in many more ways than other animals.
“Humans have the flexibility to show their smile with and without talking or laughing. This ability to flexibly use our facial expressions allows us to communicate in more explicit and versatile ways, but until now we didn’t know chimps could also flexibly produce facial expressions free from their vocalizations.”
The team also examined the types of smiles which corresponded to particular laughing sounds, and found that in many cases they matched the human laugh/smile combination, showing that the two species must have inherited the trait from a common ancestor.
ChimpFACS designer Professor Kim Bard said: “The coding system allows us to examine very subtle facial movements and compare human and chimpanzee facial expressions, based on their shared musculature.”
The study also found that ancestral apes had the capability for flexible facial expressions – i.e. smiling – thousands of years before humans evolved.
Chimps and humans are estimated to share roughly 96 percent of their genetic material, making the two species more closely related to each other than either of them are to apes or gorillas.
Before the final sequencing of the human genome it was estimated that humans and chimps shared over 99 percent of genetic material.
Humans and chimpanzees evolved from a common ancestor between 6 and 8 million years ago, analysis of DNA has shown.