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.