The answer may not be straightforward.
With a population of 41 million, Kenya is a running giant.
According to a year-old, yet still-relevant article from the Atlantic, approximately 70 to 80 percent of long-distance races since the 1980s have been won by runners from this East African country.
As a specific example of this domination, since 1988, 20 of the 25 first-place male winners at the Boston Marathon have been Kenyans. Kenyan women started later, after 2000.
So what’s the reason for all this success?
Two separate European-based studies found that young men in a small western region of the country, where most of the top talent comes from, were able to “reliably” outperform most top Western males.
These studies also found differences between the body mass and bone structure of the two groups.
Specifically, the Kenyans had less mass for their height. They also had longer legs and shorter torsos — all key traits for distance runners.
For More: The Atlantic