Lefties May Have Survived Because They're Handy in a Fight

About 10 percent of humanity is left-handed (including your humble blogger), but researchers have long wondered why the trait persists, since lefties seem to be at a disadvantage in the evolutionary race. Previous studies have found that lefties have shorter lifespans, shorter stature, and are more likely to be homosexual, three factors that make it more difficult for lefties to attract mates and reproduce. But a new study suggests that in addition to the vaunted creativity of southpaws, lefties may have simply had a tactical advantage throughout human evolution.

The study, which will be published in the Philosophical Transactions of the Royal Society B, surveys the existing literature and weighs the costs and the benefits of being left-handed. The study suggests that lefties have the element of surprise in one-on-one competitions, whether they’re serving tennis balls or attacking their enemies with knives. Study co-author Charlotte Faurie explains that because left-handers are less common, “their opponents will be surprised by the way they fight, and this will provide [lefties] an advantage,” she added. “It’s exactly the same in tennis or in boxing or in any sport where there is face-to-face opposition,” Faurie added [National Geographic News].

In a previous study of traditional tribal cultures, Faurie found that homicides resulting from violent fights were more frequent in societies with a higher percentage of lefties. And “because left-handers have a strategic advantage in fights, [left-handers] become more frequent generation after generation, through natural selection,” Faurie said—though those gains are tempered by the evolutionary disadvantages. Fight winners, she said, also “attract more sex partners and are therefore more likely to reproduce” [National Geographic News].

It’s still not clear what makes someone left-handed. Researchers say there’s certainly a heritable component but also say that hormone exposure in the womb may play a role. Regardless of how they come to be, many lefties face challenges once they make it out into the world, the new study says. It points to statistical surveys that suggest right-handers generally live longer than left-handers, by a few months or even several years. Why this is the case is unclear. It could be partly explained by the greater number of fatal accidents involving left-handed men grappling with industrial tools, machines and instruments designed for right-handers [AFP]. Lefties have also been shown to have a greater risk of schizophrenia, epilepsy, autism, and learning disabilities.

Related Content:
Discoblog: Why Do So Many Lefties Play Baseball? It’s Built for Them
DISCOVER: The Biology of Handedness explores how lefties come to be
DISCOVER: Thumb’s the Word reveals a way to distinguish lefties while they’re in the womb

Image: storem