Is a great sprinter made or born?

There has been much discussion on the so called genetic basis to the incredible distance runners from the Great Rift Valley in Africa. But what of the sprinters? Usain Bolt is the athlete of his generation, and the greatest sprinter of all time.. what's his deal?

Ben Johnson may not be the best example to us all as a sprinter, but man I used to love watching him run! I can taste the disaapointment of Seoul after it was revealed he was a drug cheat. Johnson, although running for Canada, was born in Falmouth, Jamaica, just like the current crop of world beating sprinters.