Evolution Of Left-Handedness?

Which brings me to Charlotte Faurie and Michel Raymond, a pair of French scientists who study the evolution of handedness. Left-handedness is partly heritable and is associated with significant health risks. So why, they wondered, hasn't natural selection trimmed it away? Were the costs of left-handedness cancelled out by hidden fitness benefits? 

The scientists noted that lefties have advantages in sports like baseball and fencing where the competition is interactive (but not in sports, like gymnastics or swimming, with no direct interaction). In the elite ranks of cricket, boxing, wrestling, tennis, baseball and more, lefties are massively over-represented. The reason is obvious. Since ninety percent of the world is right-handed, righties usually compete against each other. When they confront lefties, who do everything backwards, their brains reel, and the result can be as lopsided as my mauling by Nick. In contrast, lefties are most used to facing righties; when two lefties face off, any confusion cancels out. 

Faurie and Raymond made a mental leap. The lives of ancestral people were typically more violent than our own. Wouldn't the lefty advantage in sports—including combat sports like boxing, wrestling, and fencing—have extended to fighting, whether with fists, clubs, or spears? Could the fitness benefits of fighting southpaw have offset the health costs associated with left-handedness? In 1995 Faurie and Raymond published a paper supporting their prediction of a strong correlation between violence and handedness in preindustrial societies: the more violent the society, the more lefties. The most violent society they sampled, the Eipo of Highland New Guinea, was almost thirty percent southpaw.