Marius's posts are interesting, based on considerable first-hand experience, and deserve to be weighted more heavily than posts by those of us who have never been to Kenya--me, for example.
This particular issue--how to explain extraordinary Kenyan running success over the past 15-20 years--has been hammered to death, here and at coolrunning.
I'm leery of all explanations that employ the word "genetic," frankly. Much damage has been done to black people down through history by commentators who used that word. In the past, it was mostly the phrenologists and self-styled "racial scientists" who spoke of racial inferiority, not superiority. The shoe seems to be on the other foot these days, but I'm not so sure. I hear a lot of agitation: white racial agitation.
Still, it's probably worth flipping the script and imagining, if you would, that Kenyan power-lifting websites are filled with Kenyan angst about how Central Europeans and Samoans are simply....well...genetically gifted in the matter of being able to lift huge weights. Would that be true? Is there something about the Central European/Scandinavian and Samoan genetic makeup that enables such peoples to dominate the World's Strongest Man competition? Maybe there is. Maybe there isn't. But certainly you don't see a lot of Kenyans--ANY Kenyans--participating. I make this observation to no particular point; I'm just making it.
Although I can't say how things will change, I tend to think that the all-time fastest lists in various track events won't necessarily reflect the same overwhelming preponderance of Kenyans in, say, 50 years as they do today. Fifty years ago, in the mid-1950s, what sort of generalizations about "natural talent" or "physical endowment" were being made about distance runners, and from which particular countries? I suspect that Finnish, Czech, and Anglo-Australian stock was up--as Kenyan stock is up today.
But things change. Today's absolute certainties have a way of becoming yesterday's news.
Once genetic engineering becomes a reality in the West, it will be interesting to see what happens. I can imagine some running-oriented American parents checking the box for "Kenyan V02." Assuming it's all genetic, of course.
I know the Meb story. But I'd still like to see some experimental science, on the human-level. Take ten Kalenjin infants, ten caucasian-American infants; bring them up in each other's native habitat. Do genes tell the whole story? Or do you get paunchy Kenyan-American X-Box addicts and lean/mean kickass Caucasian-Kalenjin XC monsters?