Why are so few people left-handed?

Today marks the 22nd annual International Left-Handers Day. To celebrate, let's look at why only around one in ten people is left-handed. Why, pray tell, are lefties are so rare – or, said another way, why are most of us righties? It seems like a simple question, but it's actually one of the biggest mysteries in all of science.

http://io9.com/why-are-so-few-people-left-handed-1621011048