Scientists have been unable to pinpoint a definitive timeline for when man developed distinctive handedness. While some primates today show a clear preference for one hand over the other, there is less concrete evidence about our prehistoric ancestors. It’s believed that by the end of the mid-Paleolithic era, roughly 30,000 years ago, about one-quarter of Neanderthals used their left hand, a percentage that decreased continuously until leveling out at its modern levels. Today, roughly 10-15 percent of the global population is left-handed (and roughly 300,000 Americans) and even fewer, just one percent, are considered truly ambidextrous.
Perhaps owing to their role in the minority of every society, left-handers were looked upon with suspicion and fear throughout much of history. Nearly every culture had their own negative connotations for those using their left hand, and even language helped contribute to the stereotypes. The English word “left” is derived from an Anglo-Saxon phrase meaning broken or weak, while both Italian and German utilized phrases meaning crooked, maimed or maladroit—and the Oxford English Dictionary itself once defined left-handed with terms such as crippled, defective, and even ill-omened. For thousands of years, children born with a left-handed preference were often forcibly taught to use their right hand instead for fear of being deemed dangerous or different.
If scientists have been baffled by the historic trends in handedness, they’re also not sure what causes such preferences to begin with. It’s believed that genetics are likely at play: A child with two-left handed parents has a 25 percent chance of being left-handed. But environmental factors may also play a role. A set of identical twins can include children with different hand preferences. Recent studies have suggested that left-handedness may be, in part, the result of fetal trauma or damage in the womb, although this does little to explain the overrepresentation of “lefties” in some fields or other biological inconsistencies such as the fact that men are more likely to be left hand dominant than women.
Nor does this research explain an unusual trend in American politics. Despite the fact that just 1 in 10 Americans is left-handed, three of the last four men elected president have been southpaws—George H.W. Bush, Bill Clinton and Barack Obama. In fact, in 1992, the same year International Left-Handers Day was first celebrated, all three presidential candidates (George H.W. Bush, Bill Clinton and Ross Perot) were left-handed, a feat that was repeated 16 years later when Barack Obama and John McCain, two more “lefties”, faced off in 2008. There’s also evidence of earlier left-handed presidents, though the official record gets a bit murkier: Both Harry Truman and Ronald Reagan are believed to have been natural lefties forced to switch to using their right hands as children. Both men appeared in photos (and, in Reagan’s case, movies) where they appeared to favor their left hand for certain activities. And while some have claimed Herbert Hoover belongs in the presidential southpaw club as well, there is no hard evidence that he was left-handed, according to the Hoover presidential library.
Two other presidents can lay claim to being the only known ambidextrous commanders-in-chief. James A. Garfield ensured a hardscrabble youth before finally saving up the funds to attend college (first in his native Ohio and later at Massachusetts’ Williams College), where he developed a lifelong love of classical languages. By young adulthood, Garfield was so dexterous he was reportedly able to write a phrase in Latin with one hand while simultaneously writing the same phrase in Greek with the other. Gerald Ford, a talented college athlete who turned down two professional football contracts, was uncharitably lampooned for his purported clumsiness, a trait believed to be shared by many other left-handers. But he was equally capable of using his right hand as well. As he himself explained, he was “left-handed sitting down and right-handed standing up,” meaning that he wrote with his left hand, but played most sports (and threw a football) with his right.
As with most things relating to hand preference, researchers are unable to shed light on the usual electoral success of the southpaws, which has not been replicated elsewhere (only two British prime ministers have been left-handed). Politics isn’t the only place where the left-handed have excelled. One in four Apollo astronauts was left-handed, and they’ve also achieved great success in fields that rely on excellent visual-spatial recognitions skills, such as architecture and sports (particularly baseball).
While some southpaws have reached the highest rungs of success in many fields, the same can’t always be said of the community as a whole. A number of studies over the past 30 years have linked left-handedness to a variety of physical and emotional ailments, from sleeping disorders and depression to increased incidences of epilepsy and schizophrenia. Left-handed people are five times more likely to be killed or seriously wounded in accidents, a phenomena many researchers trace to the preponderance of “anti-left” handed gadgets in a predominantly right-hand orientated world.