Violent Societies Select For Southpaws presents a number of factoids supporting a fascinating thesis:
- Among the Jula (Dioula) people of Burkina Faso, the most peaceful tribe studied, where the murder rate is 1 in 100,000 annually, left-handers make up 3.4% of the population. But in the Yanomami tribe of Venezuela, where more than 5 in 1,000 meet a violent end each year, southpaws account for 22.6%.
- And the ratio of left-handers to right-handers is higher in successful sportspeople than it is in the general population, suggesting there is definite advantage to favouring the left hand or foot in competitive games, such as tennis.
- Statistical evidence links several auto-immune diseases, such as inflammatory bowel syndrome and ulcerative colitis, with left-handedness.
- As any schoolboy could tell you, winning fights enhances your status. If, in prehistory, this translated into increased reproductive success, it might have been enough to maintain a certain proportion of left-handers in the population, by balancing the costs of being left-handed with the advantages gained in fighting.