And it's little wonder why

We are bipedal, and therefore more efficient at converting caloric energy into locomotion.

We also have the ability to sweat, preventing overheating after prolonged effort.

And if the weather turns a bit warmer today (awoke to 9° F this morning), I'll be turning out about 5 miles when I get home from the office this evening. What can I say, I have that primal urge to run, even after retiring from a fairly successful stint at competitive running. It's in my blood.

H/T to Remus at the Woodpile Report for the link.