Jan 30, 2009

Science - Ancient Lefties: The History of Obama's Handedness

Heather Whipps

Something sinister is going on, and newly-inaugurated President Obama is behind it.

From the Latin for left, "sinistra," southpaw Obama is another notch for the column of left-handed presidents, now totaling eight - a proportion (out of all 43 men who have been POTUS) that is well above their representation in the total population, which hovers around 10 percent.

(Let's count James A. Garfield as a lefty, although some say he was ambidextrous and others say he was a lefty; many ambis are lefties who learn to do some tasks with their right hands.)

In fact, every president since 1974 with the exception of Jimmy Carter and George W. Bush has been left-handed, as is Obama's former Republican opponent Sen. John McCain. Al Gore is too.

Is it just a coincidence, or is there something about being left-handed that can make for a more presidential demeanor?

Some evolutionary advantage, whether overall greater intelligence or language skills, has kept a stable group of lefties for at least the past 200,000 years, said Chris McManus, professor of psychology and medical education at University College London.

Left-handed tools chipped 500,000 years ago

There have been lefties for as long as there have humans, historians agree.

Some of the oldest evidence of left-handedness comes from Kenya, where of a 500,000 year-old cache of 54 stone tools made by one of our pre-human ancestors, six (or about 11 percent) were chipped using the left hand. Similarly, Neanderthals working with meat and stone tools more than 150,000 years ago left marks on their teeth at left and right angles - indicating opposite hand use - in almost perfect proportion with today's 9:1 ratio.

Paleolithic cave paintings from France and Spain also hint that lefties walked among our ancestors about 30,000 years ago. Studying a collection of so-called negative hand drawings on the cave walls - similar to tracing one hand with the other - scientists found that individuals drew their left hand much more frequently than the right.

The laundry list of lefties goes on through history, with records telling us that a number of famous ancient figures probably favored their southpaw as well, from Alexander the Great to Charlemagne, Holy Roman emperor.

Though ancient sample sizes are small and poor estimates of the exact proportion of lefties, the existence of left-handedness is clear even hundreds of thousands of years ago, McManus said.

Left tied to language

Despite its long history, left-handedness is a uniquely human trait. Chimpanzees and gorillas, with whom we share an ancestor and a number of common physical attributes, don't seem to favor one hand over the other.

Instead, left-handedness may have developed along with another characteristic known just to humans - language.

Most people process language in the left side of their brain, the hemisphere that also controls the right side of the body, and have done so presumably since humans started chatting a few hundred thousand years ago. Whichever gene made the left side of our brains responsible for language also played a role in making our right side dominant, experts such as McManus believe.

Though a specific left-handed gene has yet to be found, the trait to choose one hand over the other is likely inherited, agree scientists. Left-handed parents are far more likely to produce left-handed children, and those children appear to begin favoring that hand in the womb, according to a 2004 study on 10-week-old fetuses.

More recent research suggests that, while developing, the two sides of the brain actually "fight" for specialized control of certain functions, such as handedness, with the left side (which controls the right - are you following?) more often coming out on top.

Interestingly, even when the right side wins, the left brain often shares some of the duties, studies have shown. So while right-handed people usually process language exclusively in the left side of their brain, lefties process language mostly in the right but partly on the left as well.

That preferential wiring may make lefties more adept at certain skills required for leadership according to McManus, who wrote about his theories in his book "Right Hand, Left Hand" (Harvard University Press; 2002).

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