Chimps Have Variations in Smiles, Just Like Us

by Monica Joshi

If you smile, I smile. A smile is contagious. So much so that we actually share the variations in our smiles with chimps. A new study has revealed that chimpanzees have the same types of smiles as humans when laughing, and don't even need to make a sound to be understood. This suggests that these smile types evolved from positive expressions of ancestral apes.

The new research from the University of Portsmouth suggests that chimpanzees’ communication is more similar to humans than we had previously known. The research also found that chimpanzees are able to produce these smile types silently, without being constrained by the accompanying laughing sound. In other words, they don't have to make any sounds at all while expressing happiness.

Lead researcher Dr. Marina Davila-Ross from the University’s Centre for Comparative and Evolutionary Psychology said:

“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.”

Dr. Davila-Ross and colleagues aimed to study the facial expressions of primates to uncover the evolutionary origins of human laughter and smiling. The study included researchers filming 46 chimpanzees at the Chimfunshi Wildlife Orphanage. They then used ChimpFACS, a facial-action coding system designed for chimpanzees, to measure their facial movements.

Professor Kim Bard, co-author of the paper and designer of ChimpFACS, said that:

“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 investigated specific types of smiles that accompany laugh sounds and found that these smile types have the same evolutionary origin as human smiles when they are laughing. It suggests that these smile types of humans must have evolved from positive expressions of ancestral apes.

The study makes the claim that flexibility in facial expressions could have already been present in ancestral apes and emerged long before humans evolved.

Dr. Davila-Ross acknowledges that there are still key differences between humans and our ape ancestors when it comes to the very specific facial features:

“Chimps only rarely display crow’s feet when laughing, but this trait is often shown by laughing humans. Then, it is called Duchenne laughter, which has a particularly positive impact on human listeners.”

A number of recent studies have shown that chimpanzees are quite similar to us in many different ways. For instance, they display the brain power needed to cook, show a fondness for alcohol and even exude confidence when they know they're right. These findings come at a time when animal rights groups are trying to persuade courts to treat beings with complex cognitive abilities, such as chimpanzees, as legal persons who should not be in captivity.

It would be interesting to see further research done on other animals regarding whether they display any of these characteristics while laughing. I have always suspected that my cat smiles in her sleep or when I am rubbing her belly — at least she looks like she does, and science still needs to prove me right or wrong.