baby ape, baby orangutan, tickled ape, ape laughter, laughing orangutan
AP/University of Portsmouth, Miriam Wessels
A baby orangutan, Naru, laughs while being tickled.

Baby Apes Shed Light on the Evolution of Laughter

June 08, 2009 08:00 AM
by Haley A. Lovett
Laughing is not unique to humans. Researchers tickled infant apes and infant humans and found that the sounds created by the apes indicated a common ancestral link for laughter.

Do Apes Laugh? Scientists Say Yes

In order to test the hypothesis that the human expression of emotion originated from an ancestor shared by humans and apes, scientists Marina Davila Ross, Michael J. Owren, and Elke Zimmermann conducted a study of infants of primate species.

The study, published in Current Biology, looked at the tickle-induced sounds made by infant orangutans, gorillas, chimpanzees, bonobos and humans (all, including humans, considered to be great apes). 

ScienceDaily reports that when the scientists studied the sounds created by the apes and humans, they found that the evolutionary relationships among how similar the animals’ sounds were correlated with the known evolutionary genetic relationships of the animals, which supported the theory that there was a common evolutionary origin for the laughter.

According to LiveScience the researchers also discovered something surprising in the sounds of two apes—the gorillas and the bonobos. Humans were once thought to be the only species that could control its breathing patterns, which may be why humans can speak. One way that humans control breathing is by only emitting laughing sounds while exhaling, and often laughing longer than a normal inhale-exhale breathing cycle. The gorillas and the bonobos also laughed in this way, showing that they too had control over breathing patterns.

One author of the study, Davila Ross, told LiveScience that the study indicates that it was a pre-human development, and that “[i]t is likely that great apes use laughter sounds to interact in similar ways to humans.”

Background: Apes more like humans than once thought

In the past few years, scientists have discovered more behavioral links between apes and humans than once previously thought.

In April, scientists released a study that found that some chimpanzees give away meat in order to secure future mating partners, showing that the animals had the capacity to plan for a future encounter with a female. The two-year study looked at a group of chimps and found that males gave away meat to ovulating and non-ovulating females, even though chimps only mate with ovulating females. The study also found that a chimp’s chances of mating with a female at a later time doubled if he’d given her meat.

Zookeepers in Sweden were surprised when, in 1997, they realized that one of their chimps, Santino, had collected stones one morning to throw at visitors later in the day. A scientist then began studying Santino’s behavior and concluded that the chimpanzee had in fact planned the attacks, showing that he was preparing each morning in a calm state for a later state of anger.

Related Topic: Laughter as Medicine

In observation of national humor month (April) findingDulcinea discussed why laughter is is known as the best medicine. In 2005 scientists studied participants who watched comedy films and found that blood flow increased and blood pressure dropped. Scientists have also found that laughter is much more common in social situations, as it is a sign to others, and that solitary people are less likely to laugh.

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