August 15, 2005

Some chimps are left-handed, study finds

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

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.