Behind every sport is a story about genetics. Not a story about the science of genetics, or even a self-conscious awareness of the genetic basis of much that distinguishes athletes (as it does for the rest of us). But in the selection of players, in the rules of our games, and in the biases that sprinkle sports history, genetics lurks as a hidden factor. It is only in the past hundred or so years that the genetic basis of our athletic profiles and abilities has become evident. And only in the last 50 or so years have we imagined that we could begin to control the genetic determinants of athletic prowess.