The Left-Handed Advantage

William Hopkins, a psychologist at Emory University's Yerkes National Primate Research Center, has found most chimpanzees use their right hands for a number of functions, from throwing a ball to scooping peanut butter from a tube. Furthermore, he and his colleagues have linked this handedness to the KNOB, an area of the brain associated with motor activity, not language.

Hopkins further points out that chimps don't have language, so why would there be a majority of right-handed chimps? As among humans, being in a minority when it comes to handedness has its advantages.

"The advantage is at the individual level," said Giorgio Vallortigara, a psychologist at the University of Trieste in Italy. "The advantage is observed only until the minority group remains a minority. If the number of individuals that do not share the side preference that most do increases, then the advantage is lost."

Swimming Their Own Way

Vallortigara has studied how this works in certain schools of fish. Some fish swim in large groups, or shoals. Traveling in a pack provides individuals with extra protection from predators. Most of the fish in the group share the same tendency to keep an eye out on one side or the other for predators and to flee in a particular direction if a threat is seen.

Minority-sided fish, meanwhile, are likely to watch the other way and turn and flee in the opposite direction. While these fish miss out on the protection of the group, they gain the element of surprise -- predators don't expect them to turn in the opposite direction from the group.

Similar examples can be found among birds and toads. In each case individuals that favor an unusual side find some benefit, be it surprising predators with the direction of their flight or by finding resources that might elude the majority.

Still, researchers point out that, at least among humans, genetics is not the only factor behind left-handedness.

Evidence has shown a link between trauma during gestation or during birth, as well as in the age of the mother and so-called pathological left-handedness. Numbers show that mothers who are over 40 at the time of their child's birth are 128 percent more likely to have a left-handed baby than a woman in her 20s.

"Handedness is controlled by a whole lot of pathways in the brain and if any one of these pathways is mucked up during gestation, then handedness becomes a cosmic dice game," said Stanley Coren, a psychologist at the University of British Columbia and author of "The Left-Handed Syndrome." "We believe this accounts for about half of all left-handers."

It could be that this early trauma is also the trigger behind health problems linked to left-handedness. Coren points to two famous left-handers, Presidents Bill Clinton and George H.W. Bush, as evidence. Both had histories of birth stress and have health issues from Clinton's severe allergies to Bush's Graves' disease.

Then again, as many lefties might point out, being left-handed can also offer intellectual prowess. Tests conducted by Alan Searleman from St Lawrence University in New York found there were more left-handed people with IQs over 140 than right-handed people. Famous left-handed thinkers in history from Albert Einstein to Isaac Newton to Benjamin Franklin seem to underline the point.

As Hopkins says, it may be that left-handed people occupy the extremes when it comes to health and ability.

"The anomaly is left-handed people make up the extremely gifted and the extremely compromised," said Hopkins. "The rest of us make up the middle ground."

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