If a cheetah（猎豹）, a wolf and a well-trained human all entered a marathon, who would win?
The cheetah would definitely take an early 1 . The wolf would probably pass the cheetah after a few miles. But at the end of the 26 miles, the human would be the first to cross the 2 line.
Humans have only two legs but a（n） 3 capacity for running. Our powerful lungs give us the stamina needed to run great distances. And because we can sweat, we can control our body 4 while we run. Why are we so good at running? Running was necessary for early human 5 . Of course, we don't often need to run for survival these days. All the same, running 6 to play an important role in human cultures all over the world.
Marathon running is perhaps the best-known example of human running 7 . That is because it is a big business. Millions of people worldwide watch on television as elite runners 8 for millions of dollars. And, of course, businesses 9 products such as athletic shoes during the competition.
How does someone become an elite marathoner? The 10 runners of Kenya seem to have found the answer. Iten is a small farming town in Kenya's western highlands. It is also home to seven of the world's top ten marathon winners. Most of them are 11 of the Kalenjin tribe. They tend to have 12 bodies for running. Their slim bodies, long legs and short waists concentrate 13 where a runner needs it most — the legs.
And because Iten is 8,000 feet above sea level, the Kalenjini 14 an enormous lung capacity. They need it to get oxygen out of the thin air. This gives the Kalenjini an important 15 when they compete in races at lower altitude.
