Friday, June 05, 2009

After All, If You Can't Laugh at Yourself...

The June 4 issue of Current Biology contains a study indicating that laughter goes back beyond the ape-human split. The article, in Thaindian reports:
“This study is the first phylogenetic test of the evolutionary continuity of a human emotional expression,” said Marina Davila Ross of the University of Portsmouth in the United Kingdom.

“It supports the idea that there is laughter in apes,” she added.

To reach the conclusion, researchers analysed the recorded sounds of tickle-induced vocalizations produced by infant and juvenile orangutans, chimpanzees, gorillas, and bonobos, as well as those of human infants. A quantitative phylogenetic analysis of those acoustic data found that the best “tree” to represent the evolutionary relationships among those sounds matched the known evolutionary relationships among the five species based on genetics.

The researchers said that the findings support a common evolutionary origin for the human and ape tickle-induced expressions.They also show that laughter evolved gradually over the last 10 to 16 million years of primate evolutionary history.

But human laughter is nonetheless acoustically distinct from that of great apes and reached that state through an evident exaggeration of pre-existing acoustic features after the hominin separation from ancestors shared with bonobos and chimps, about 4.5 to 6 million years ago, Davila Ross says.

Uh, not 4.5 to 6 mya. Not if Orrorin and Sahelanthropus represent incipient hominids. More like 9 to 10 mya. Still, it is nice to know we share such a stress-reducing behavior.

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