Wednesday, August 17, 2005

Study: Chimps show hand preference

Tuesday, August 16, 2005 Posted: 0536 GMT (1336 HKT)
(WASHINGTON (Reuters) -- Wild chimpanzees can be left or right-handed just as humans are, researchers reported on Monday in a study that sheds light on the evolution of "handedness".
A study of 17 wild chimpanzees in Gombe National Park in Tanzania shows that most preferred to use their left hands when fishing for termites, although they used their right hands for other tasks such as cracking nuts.
"Handedness runs in families of wild chimpanzees, with offspring hand use resembling the hand preferences of their mother," Elizabeth Lonsdorf and William Hopkins of the Yerkes National Primate Research Center in Atlanta wrote in their report, published in the Proceedings of the National Academy of Sciences.
Chimpanzees in captivity show a right-handed preference for some tasks, but researchers have wondered if this because they are raised by humans, who are mostly right-handed.
So Lonsdorf and Hopkins watched chimpanzees to see what happened in the wild.
"Termite fishing involves precision movements that require the chimpanzees to insert small sticks into holes in dirt mounds that contain the termites," they wrote.
They said their findings suggest that the beginnings of left-brain/right-brain splits associated with hand preference had already evolved 5 million years ago, before early humans separated from the ancestors of chimpanzees.
Chickens and frogs show a type of "handedness" but some experts had argued that being left or right-handed in humans was associated with language centers in the brain.
Humans are still far more likely than chimps to be right-handed. It could be there was a genetic mutation favoring right-handedness in humans, the researchers said.
Or it could be that this is a reflection of the unique organization of human brains, they added.

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