June 3, 2009—Apes laugh too, say researchers who tickled gorillas, chimps, orangutans, bonobos, and human babies—suggesting laughter began in a prehistoric ape-human ancestor.
© 2009 National Geographic (AP); Additional video from University of Veterinary Medicine Hannover
This gorilla was tickled - literally - to take part in laughter research.
For years, scientists have argued about the concept of natural selection and evolution.
But now researchers say this playful scene reveals yet another extraordinary resemblance between ourselves and our furry cousins.
This gorilla, according to scientists, displays the same response that we do when we are tickled.
It doesn't sound much like human laughter, it's more like rapid panting, or slower noisy breathing or a short series of grunts.
Marina Davila Ross has spent years tickling and carefully documenting the behavior of apes and then making minutely detailed measurements of their vocal reactions.
She compared the ape sounds to the chuckles made by human babies- in all, more than 800 recordings. And her study wasn't confined to gorillas.
She's examined the traits of bonobos, orangutans and chimps as well.
SOUNDBITE: (English) Marina Davila-Ross, Primatologist, University of Portsmouth "I was very much excited particularly after we have found out that laughter can be traced back all the way to ten, at least ten to sixteen million years. We've used the acoustic data in order to see how it has changed, what kind of changes occurred and when they occurred. We found that particularly over the last five million years there were a lot of changes occurring, and these changes led to human laughter becoming quite unique".
The results of these studies enhance what many scientists already knowthat all primates are able to express positive emotions like joy.
SOUNDBITE: (English) Marina Davila-Ross, Primatologist, University of Portsmouth "One very interesting thing we found in our laugh data was that gorillas and bonobo's can extend their exhalation phase when they are laughing so they are breathing out for a very long time and that is a characteristic that was thought to be humanly unique, it plays a very important role in speech for instance"
Davila Ross conducted the study with colleagues from Georgia State University in Atlanta, and the University of Veterinary Medicine in Hannover, Germany.
After measuring traits of each species' laughter sound, the researchers mapped out how these sounds appeared related to each other.
The result looked like a family tree which matched the way the species themselves are related.
She also concluded that while human laughter isn't that similar to ape versions, its distinctive features could well have arisen from shared ancestral traits.