WASHINGTON – When it comes to fishing tasty termites out of their mounds, wild chimpanzees don't have the right stuff. Most, in fact, are southpaws.
A three-year study of 17 wild chimps in Gombe National Park (search), Tanzania, found that 12 of them used their left hands when using sticks to probe for termites.
Four were right-handed and one was listed as ambiguously handed.
"Contrary to previous claims, wild chimpanzees show population-level handedness in tool-use," reported the research team led by William D. Hopkins of the Yerkes National Primate Research Center (search) at Emory University in Atlanta. Population-level handedness indicates a preference for one hand in a large group.
Hopkins' findings are reported in Tuesday's issue of Proceedings of the National Academy of Sciences.
The paper also looked at previous studies of chimpanzees and found that others had noted a left-handed preference when using sticks to fish for termites, but there had been reports of a right-handed preference when cracking nuts.
Scientists have long debated whether nonhuman primates exhibit handedness.
Because the hands are controlled by opposite sides of the brain, the finding could indicate that this brain division had begun as long as 5 million years ago, prior to the split between humans and chimpanzees.
Richard W. Byrne (search) of the University of St. Andrews in Fife, Scotland, who has reported on hand-preference in mountain gorillas doing complex tasks, said: "It now looks as if whatever gives a population skew to manually skilled behavior has its roots deep in the shared ancestry of humans and all other African great apes."
Byrne, who was not part of Hopkins' research team, said the findings show that with a big sample of chimpanzees there is a slight but real group hand-preference when chimpanzees fish for termites, although many previous researchers with smaller samples had concluded there was not.
Among humans, a right-handed preference has been estimated for about 90 percent of the population. But Byrne noted that the figure "depends on asking people which hand they write with, and in studies of nonliterate people's behavior, much lower figures [for right-handedness] are found."
A larger question concerns the evolution of language, Hopkins said in a telephone interview.
Most people, right and left handed, use the left hemisphere of the brain to process language, he explained.
The argument has been made that if humans developed language after the split from apes, and language is related to handedness, then there shouldn't be handedness in apes, he said,
"This reinforces the view that the whole historical link between language and handedness is probably not a correct one and people need to rethink those ideas," Hopkins said.