A naked, sweating animal

"Actually, Dr. Bramble was surprised to find that all runnning mammals are restricted to the same cycle of take-a-step, take-a-breath. In the entire world, he and David could only find one exception:
You.
«When quadrupeds run, they get stuck in a one-breath-per-locomotion cycle,» Dr. Bramble said. «But the human runners we tested never went one to one. They could pick from a number of different ratios, and generally, preferred two to one.» The reason we're free to pant to our heart's content is the same reason you need a shower on a summer day; we're the only mammals that shed most of our heat by sweating. All the pelt-covered creatures in the world cool off primarily by breathing, which locks their entire heat-regulating system to their lungs. But humans, with our millions of sweat glans, are the best air-cooled engine that evolution has ever put on the market.
«That's the benefit of being a naked, sweating animal,» David Carrier explains. «As long as we keep sweating, we can keep going.»

Christopher McDougall, Born to run, Chapter 28.

The secret of the Tarahumara

"That was the real secret of the Tarahumara: they'd never forgotten what it felt like to love running. They remembered that running was mankind's first fine art, our original act of inspired creation. Way before we were scratching pictures on caves or beating rhythms on hollow trees, we were perfecting the art of combining our breath and mind and muscles into fluid self-propulsion over wild terrain. And when our ancestors finally did make their first cave paintings, what were the first designs? A downward slash, lightning bolts through the bottom and middle-behold, the Running Man."

Christopher McDougall, Born to run, Chapter 15.

"When you run on the earth and run with the earth, you can run forever."

Tarahumara's saying.