April 20, 2011 at 4:13 PM ET
Lefties were as outnumbered 600,000 years ago as they are today, according to telltale markings on teeth found on Neanderthal and Neanderthal ancestors in Europe.
The finding serves as a new technique to determine whether a person was left- or right-handed from limited skeletal remains, and it also suggests that a key piece for the origin of language was in place at least half a million years ago, David Frayer, an anthropologist at the University of Kansas, told me today.
But while ancient righties appeared to outnumber lefties nine to one, the findings don't reveal whether some of the ancient lefties dominated in sports, as baseball players do today; and in politics, where being left-handed seems to help open the door to the White House.
The telltale tooth markings, based on experiments, appear to result from how these Neanderthals and their relatives processed hides with stone tools, explained Frayer, a co-author of a paper on the findings published this month in the journal Laterality.
One of his colleagues in Spain had people wear a mouth guard and then strike a hide as if they were cutting or stretching it with a stone tool. Every now and then, the test subjects were asked to whack their guarded teeth, as the researchers think would have accidentally happened as the ancient humans worked away.
Imagine a person pulling on the hide with their left hand and striking it with a tool held in their right hand. When they accidentally hit a tooth, the angle of the strike would be from the upper left to the lower right, Frayer explained.
"It doesn't matter what tooth it was, it would always be in that direction," he told me. "That tells you if you see scratches that are running in that direction, it tells you that the individual was primarily using their right hand to process."
Markings primarily going the opposite way — from the upper right to the lower left — are the sign of a lefty.
Frayer and colleagues examined isolated teeth from 27 Neanderthal and Neanderthal ancestors from Europe dating back 600,000 years and found that 25 of them have the telltale markings of a righty.
"That's the pattern we see in modern populations," Frayer noted, suggesting that right-handed dominance is an ancient human trait.
Although some studies of tool-using chimpanzees suggest a preference for the left hand, the ratio isn't as sharp as 9 to 1, according to Frayer. Such a distinctive ratio of handedness is unique to humans and their immediate ancestors and relatives.
And such laterality, he adds, appears linked to the development of language, a skill that humans have and chimps don't.
"The connection is the left side of the brain controls the right side of the body, and language is located on the left side," Frayer said.
We know this because when people experience a stroke on the left side of the brain, their speech is impaired and they lose control of the right side of their body. A person who has a stroke on the right side of the brain retains the ability to talk, but loses control of the left side of their body.
Finding that right-handedness goes back at least 600,000 years thus suggests that this key piece for language was in place, "so the people probably spoke," Frayer said.
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