We've created an unnatural form of running. It's not just the shoes, but we run on artificial surfaces - straight ahead, hard and steady - instead of speeding up and slowing down, reacting to the terrain with changes of pace and rhythm.

Extreme heroism springs from something that no scientific theory can fully explain; it's an illogical impulse that flies in the face of biology, psychology, actuarial statistics, and basic common sense.

Even Charles Darwin, that human decoder ring of bizarre behavior, found the idea of saving a stranger's life to be a total head-scratcher.

I have the idea that running shoes are based on a kind of cult idea - that our feet are flawed and we need shoes to correct those flaws. The shoe companies are in the business of selling shoes. But there's no evidence from running shoe manufacturers that they're right. There's no scientific data that running shoes reduce injury.