Hugh Pickens writes writes "Representing only 10 percent of the general human population, scientists have long wondered why left-handed people are a rarity. Now a new study suggests lefties are rare because of the balance between cooperation and competition in human evolution and a mathematical model was developed that predicts the percentage of left-handers by sport based on each sport's degree of cooperation versus competition. “The more social the animal—where cooperation is highly valued—the more the general population will trend toward one side,” says study author Daniel M. Abrams. “The most important factor for an efficient society is a high degree of cooperation. In humans, this has resulted in a right-handed majority.” If societies were entirely cooperative everyone would be same-handed, but if competition were more important, one could expect the population to be 50-50 because cooperation favors same-handedness—for sharing the same tools, for example while physical competition favors the unusual. In a fight, for example, a left-hander would have the advantage in a right-handed world. The mathematical model accurately predicted the number of elite left-handed athletes in baseball, boxing, hockey, fencing, and table tennis (PDF)—more than 50 percent among top baseball players and well above 10 percent (the general population rate) for the other sports. For other sports like football or hockey where team cooperation is paramount, it is ideal for all individuals to possess the same handedness. For example, in football, blocking schemes are often designed to protect a quarterback’s blind side. As a result, it is benecial for all quarterbacks on the roster to possess the same handedness to minimize variations of the offensive sets. "The accuracy of our model’s predictions when applied to sports data supports the idea that we are seeing the same effect in human society.""