Evidence accumulates that there are slight genetic advantages of Kenyans from the Rift Valley which help them run better at distance. These include less bulky calves and ankles, more slow-twitch fibers in their muscles, and (somewhat relatedly) more efficient use of oxygen by the muscles. West Africans, in contrast, are seen as having some genetic advantages that make them better in explosive strength sports, such as sprinting or jumping.
It bothers some people no end that there might be genetic advantages in one group versus another, because who knows where that might lead? So they go to great lengths to prove that all differences are environmental. This can lead to ridiculous claims. The study's data points screamingly points to genetic factors, which for some unexplainable reason, the article insists are environmental factors.
That said, it pays to be clear exactly what "genetic factors" mean.
1. At an elite level, even slight advantages may be great.
2. Traits we regard as under our control, such as tenacity, coachability, or pain threshold, might be just as heritable as calf size.
But most importantly, 3. Each of these traits is a single advantage, not a general advantage for "modern distance running." There has been no selection over the past 10,000 years for traits that will make you "travel across the ocean and run specific distances on the flat in special shoes." There are any number of traits that could be advantageous in distance running, or any other sport. The Kenyans have a specific suite of tiny genetic advantages. Other combinations of genetic difference might work as well, or better. Frank Shorter had a VO2 maximum that exceeded that of the Kenyans. Put that together with one other genetic trait and it might be a world beater.
This has larger implications for all genetic differences between groups. A demonstrated advantage in reflexes, IQ, cold tolerance, stress tolerance, or nasal cuteness might be quite real, but not the whole story. Genes matter, and those who play the "follow your dreams" game of pretending otherwise are being viciously cruel to young people. But there is more than one way to skin some, if not all cats. A little wisdom, a little perspective, and something similar to the dream might be found.