Evolutionary theory has long been puzzled by left-handedness. Southpaws are in the minority, and they get into many more accidents than do the right-handed; in the modern context, this is partly because so many quasi-lethal tools are engineered primarily for right-handed use. So the question is, given that left-handedness is so dangerous to one’s health, why haven’t southpaws evolutionarily vanished?

Possibly because southpaws are extremely good at one thing: Killin’ people. In a recent Proceedings of the Royal Society, professors Charlotte Faurie and Michel Raymond published a study noting that left-handed people traditionally excel at combat sports, such as fencing and boxing, because their attacks so flummox the majority of opponents who are overaccustomed to right-handed attacks. They theorized further that this would mean that societies prone to violence would have an overabundance of left-handed people. When they gathered some data, it seemed to support their hypothesis; as The Economist summarized their findings:

One of the highest proportions of left-handers, for example, was found among the Yanomamo of South America. Raiding and warfare are central to Yanomamo culture. The murder rate is 4 per 1,000 inhabitants per year (compared with, for example, 0.068 in New York). And, according to Dr Faurie and Dr Raymond, 22.6% of Yanomamo are left-handed. In contrast, Dioula-speaking people of Burkina Faso in West Africa are virtual pacifists. There are only 0.013 murders per 1,000 inhabitants among them and only 3.4% of the population is left-handed.

You can read the actual paper itself online here in PDF format.

(Thanks to John for this one!)