[bluetech]

Have you heard of persistence hunting? Here's is a short documentary from the BBC: https://www.youtube.com/watch?v=826HMLoiE_o

It is believed to be one of the oldest hunting techniques, and so would indicate that humans are in fact meant to run long distances. According to Wikepedia, the runner runs for "about two to five hours over 25 to 35 km (16 to 22 mi)".

[macspoofing]

The fact that the rest of humanity didn't bother with persistence hunting may also be a clue that we weren't designed for that either.

[adrianN]

Or it's a clue that we figured out that building a trap or using a weapon to kill an animal from greater distance burns a lot less calories.

[macspoofing]

For sure. And that's the point. Persistence hunting is a strategy developed by a set of humans living in one small area of the world that isn't particularly hospitable to humans. In fact, give how inhospitable the African Savannah is, it is a point against the idea that this is somehow a 'natural' state of being for us. And it makes sense, this kind of long distance running is incredibly energy intensive and injury prone - it's not a great way to make a living.

[bluetech]

It is not as clear cut as you say, there appears to be some scientific discussion on this: https://en.wikipedia.org/wiki/Endurance_running_hypothesis