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Ha-Ha! Ape study traces evolution of laughter
06/04/2009
http://www.gmanews.tv/story/164123/Ha-Ha-Ape-study-traces-evolution-of-laughter

NEW YORK ? When scientists set out to trace the roots of human 
laughter, some chimps and gorillas were just tickled to help. 
Literally.

That's how researchers made a variety of apes and some human babies 
laugh. After analyzing the sounds, they concluded that people and 
great apes inherited laughter from a shared ancestor that lived more 
than 10 million years ago.

Experts praised the work. It gives very strong evidence that ape and 
human laughter are related through evolution, said Frans de Waal of 
the Yerkes National Primate Research Center at Emory University in 
Atlanta.

As far back as Charles Darwin, scientists have noted that apes make 
characteristic sounds during play or while being tickled, apparently 
to signal that they're interested in playing.

It's been suggested before that human laughter grew out of primate 
roots. But ape laughter doesn't sound like the human version. It may 
be rapid panting, or slower noisy breathing or a short series of 
grunts.

So what does that have to do with the human ha-ha?

To investigate that, Marina Davila Ross of the University of 
Portsmouth in England and colleagues carried out a detailed analysis 
of the sounds evoked by tickling three human babies and 21 orangutans, 
gorillas, chimps and bonobos.

After measuring 11 traits in the sound from each species, they mapped 
out how these sounds appeared to be related to each other. The result 
looked like a family tree. Significantly, that tree matched the way 
the species themselves are related, the scientists reported online 
Thursday in the journal Current Biology.

They also concluded that while human laughter sounds much different 
from the ape versions, its distinctive features could well have arisen 
from shared ancestral traits.

Jaak Panksepp of Washington State University, who studies 
laughter-like responses in animals but didn't participate in the new 
work, called the paper exciting.

It's the first formal study of how chimps and other apes respond to 
tickling, a highly detailed examination that compares an unusually 
wide range of species to humans, he said.

Panksepp's own work concludes that even rats produce a version of 
laughter in response to play and tickling, with chirps too 
high-pitched for people to hear. So he believes laughter goes even 
farther back in the mammalian family tree than the new paper proposes.

Robert Provine, a neuroscientist at the University of Maryland, 
Baltimore County, who wrote the 2000 book, "Laughter: A Scientific 
Investigation," said the new paper reveals some important insights, 
like details of the ape sounds that hadn't been appreciated before. - 
AP