[386wt]

...can do that no other critter can...

That is a big clue. We we are not designed to run long distances. No other animal is either.

[null and void]

I disagree. Being able to run any nutrition rich game into the ground is what enabled us to survive and consistently get enough food operate a big brain.

Distance running is what made us human.

YMMV

[Atlantan]

Video of the Terahumaras, a Mexican tribe of long distance runners. Micah True spent time with this tribe.

http://www.youtube.com/watch?v=FnwIKZhrdt4