Beijing 2008: Usain Bolt slows down as he approaches the finish line of the the 100-meter finals. He beats his chest, well ahead of his nearest rival, his face filled with the euphoria of a young man utterly in thrall to his extraordinary physical talent. It is one of the greatest moments in sports history, and it is just the beginning. Of the ten fastest 100-meter times in history, eight belong to Jamaicans. How is it that a small Caribbean island...