why running?

Here are two ‘running and the human body’ arguments from the web:

1) When man was a hunter-gatherer, how did he catch the speedy antelope and other game which provided him with his protein? Not by chasing, but by stealth. That stealth required careful, slow, steady pacing, downwind of the animal, without rustling dry leaves or cracking underfoot... Man is not built for running, but for walking, and for walking at a slow, deliberate pace which does not send shock waves up the length of our lower limbs. (P. Arnold, 2008, BMJ)

2) Running has substantially shaped human evolution. Running made us human – at least in an anatomical sense. We think running is one of the most transforming events in human history. We are arguing the emergence of humans is tied to the evolution of running. (D. Bramble and D. Lieberman, 2004, Nature)

Arnold argues that our easily sprained ankles would have prevented primitive man from chasing game over uneven terrain for extended periods of time. In contrast, Lieberman presents 26 human traits that point towards running proficiency, for example: Narrow trunk and waist; independent movement between hips, legs, and torso; springy foot tendons and ligament. So did early man hunt like lions, using stealth to place themselves in strategic - and relatively close - proximity to prey, followed by a quick, decisive strike? Or was it more like wolves, relying on slow-twitch muscle fibers to select the weakest individual and chase it until exhaustion?

I don’t care too much either way (not interested in competitive walking) but the discussion is kind of fun. I think Lieberman’s argument is compelling, i.e., that the adaptive changes that made us better runners did not improve walking proficiency. It seems like good evidence, in other words, that early scavengers/gatherers were under selective pressures that rewarded speed (perhaps to escape rather than chase?) and that we are, therefore, at least somewhat built for running.