caryrandolph:

Last year in the United States, 425,000 marathoners crossed the finish line, an increase of 20 percent from the beginning of the decade, Running USA says. [This Sunday] about 40,000 people will take part in the New York City Marathon.

The scientific evidence supports the notion that humans evolved to be runners. In a 2007 paper in the journal Sports Medicine, Daniel E. Lieberman, a Harvard evolutionary biologist, and Dennis M. Bramble, a biologist at the University of Utah, wrote that several characteristics unique to humans suggested endurance running played an important role in our evolution.

Most mammals can sprint faster than humans — having four legs gives them the advantage. But when it comes to long distances, humans can outrun almost any animal. Because we cool by sweating rather than panting, we can stay cool at speeds and distances that would overheat other animals. On a hot day, the two scientists wrote, a human could even outrun a horse in a 26.2-mile marathon.

Great article on distance running. I highly suggest reading and clicking through to this.