Why are Kenyans such successful long-distance runners?

Is it due to High altitude, running culture, and good genes?
Most of Kenya's future Olympians are raised at high altitude, where running builds greater lung capacity as athletes grow accustomed to the thinner air. Some Kenyan children run 10 miles a day, in the hopes of using endurance running as a ticket out of poverty. More obscure theories have credited cattle herding and circumcision rituals for the Kenyans' success.

According to an article in Slate, there are a few popular theories, which break along nature-versus-nurture lines. The vast majority of Kenya's brightest running stars were born and raised at high altitude. Running at higher elevations builds greater lung capacity, because athletes grow accustomed to the thinner air. Many of the finest runners, for example, hail from the hilly region surrounding Eldoret, about 7,000 to 8,000 feet above sea level. This area also possesses a fairly mild climate that allows for year-round running.

If altitude alone determined distance-running success, of course, then Nepalese marathoners would dominate. So, perhaps a more important factor is the nation's running culture, particularly among the Kalenjin tribe. Though Kalenjins represent just 12 percent of Kenya's population, they comprise about three-quarters of the nation's elite runners.

The trend started with Kip Keino, who won Olympic gold in the 1,500 meters in 1968 and added an Olympic steeplechase title in 1972. The ex-policeman's success inspired succeeding generations of Kalenjins, who grew up idolizing Keino. As a result, Kalenjins now aspire to distance-running titles in the same way American youths dream of playing in a Super Bowl.

Although majority of the Kenyan runners are Kalenjins,there are other superstars from the Kenyan Highlands but not Kalenjins.They include Okayo, Ngugi, Kariuki,Ondieki,Ndereba,Temu,Ouko,Mutua,Muya,Keronji,Aguta,Ereng,Konchellah among others, have all held impressive world records.