Redirecting to http://m.npr.org/story/151936266?url=/blogs/health/2012/05/07/151936266/wired-to-run-runners-high-may-have-been-evolutionary-advantage Redirecting to http://m.npr.org/story/151936266?url=/blogs/health/2012/05/07/151936266/wired-to-run-runners-high-may-have-been-evolutionary-advantage.