And You Thought Mr. Monkey Was Ambidextrous!
Left-handed chimps poke holes in theory
New findings cast doubt on link between language and handedness in primates.
By Frank D. Roylance Baltimore Sun Posted August 16 2005
When chimpanzees in the famed Gombe National Park in Tanzania pick up sticks and poke them into termite mounds in pursuit of a tasty snack, most use their left hands. In fact, when researchers worked out the numbers, they found that, at least when they're fishing for termites, the Gombe are left-handed by a better than 2-to-1 margin.
By combing through previous chimp studies, researchers also found evidence that about twice as many chimps use their right hands to hammer nuts open with rocks and to sop up water with crumpled leaves. That would merely be an interesting footnote, except that the findings cast doubt on a long-held assumption about how humans evolved. It also raises questions about the notion that, as a group, only primates with language -- namely us -- can display right- or left-handedness. Humans are overwhelmingly right-handed, by a ratio of at least 8-to-1. And, because human language and right-handedness are controlled by the left side of the brain, experts have long argued that the two traits evolved together. Scientists long thought that handedness in other primates was the result of random, individual influence, with no significant pattern within large groups.
"The argument is that other animals don't have language and so shouldn't show any handedness. And that was predominantly what the data showed for many years," said William D. Hopkins, co-author of the report in Monday's Proceedings of the National Academy of Science.
The discovery that chimps show clear evidence of handedness "raises questions about that evolutionary assumption," said Hopkins, a Yerkes researcher and psychologist at Berry College in Georgia. It also suggests this left-right specialization in the brain probably evolved before the common ancestors of chimps and humans split apart 5 million years ago. Despite some evidence of right-left preferences among chickens, pigeons, frogs and fish, studies never seemed to settle the issue of handedness in man's closest relatives. Researchers who looked at captive chimps and gorillas concluded that they were mostly right-handed. But critics argued that those animals, raised among humans, might have learned their handedness from their mostly right-handed human caretakers. In the wild, studies of great apes were rare, Hopkins said.
New findings cast doubt on link between language and handedness in primates.
By Frank D. Roylance Baltimore Sun Posted August 16 2005
When chimpanzees in the famed Gombe National Park in Tanzania pick up sticks and poke them into termite mounds in pursuit of a tasty snack, most use their left hands. In fact, when researchers worked out the numbers, they found that, at least when they're fishing for termites, the Gombe are left-handed by a better than 2-to-1 margin.
By combing through previous chimp studies, researchers also found evidence that about twice as many chimps use their right hands to hammer nuts open with rocks and to sop up water with crumpled leaves. That would merely be an interesting footnote, except that the findings cast doubt on a long-held assumption about how humans evolved. It also raises questions about the notion that, as a group, only primates with language -- namely us -- can display right- or left-handedness. Humans are overwhelmingly right-handed, by a ratio of at least 8-to-1. And, because human language and right-handedness are controlled by the left side of the brain, experts have long argued that the two traits evolved together. Scientists long thought that handedness in other primates was the result of random, individual influence, with no significant pattern within large groups.
"The argument is that other animals don't have language and so shouldn't show any handedness. And that was predominantly what the data showed for many years," said William D. Hopkins, co-author of the report in Monday's Proceedings of the National Academy of Science.
The discovery that chimps show clear evidence of handedness "raises questions about that evolutionary assumption," said Hopkins, a Yerkes researcher and psychologist at Berry College in Georgia. It also suggests this left-right specialization in the brain probably evolved before the common ancestors of chimps and humans split apart 5 million years ago. Despite some evidence of right-left preferences among chickens, pigeons, frogs and fish, studies never seemed to settle the issue of handedness in man's closest relatives. Researchers who looked at captive chimps and gorillas concluded that they were mostly right-handed. But critics argued that those animals, raised among humans, might have learned their handedness from their mostly right-handed human caretakers. In the wild, studies of great apes were rare, Hopkins said.
posted by Taco Mike | 12:41 PM
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