Sprinters' success a combination of nature and nurture
(Newser) -
Jamaicans sprinters are cleaning up in Beijing, thanks to both biology and their backgrounds. Runners of West African descent—including Jamaicans—have more "fast-twitch" muscle fibers, the kind that generate quick bursts of energy, Slate explains. But nature alone didn't propel 100-meter champ Usain Bolt to his record-breaking, chest-thumping...