Human beings evolved to be able to catch game by running it down and hitting it with a club or sticking a spear in it. I mean, game like a deer, that can run twice as fast as a human, at the very least. But they can only do it for a few hundred yard (or meters, or metres, if you want to be picky). A human, in proper condition, can run all day and into the night.

One of my daughter's best friends has run 100 miles, over the mountains and through valleys with 100-degree + (F.) temperatures, in under 19 hours. And she's a Gurll...

It's just that most of us aren't in very good shape.

Peter