Why do Kenyans and Ethiopians dominate distance running?

Now that it is marathon season, its time to ask the question that so many other people who are content to just finish the marathon rather than win it are asking. Why do east Africans, usually Kenyans or sometimes Ethiopians or other groups from east Africa win so many long distance races? Besides this, many distance records are currently held by east Africans.

I remain very fascinated by this phenomenon, but really have no idea how to explain it except to say it must be due to many different factors. It goes without saying that an extreme amount of training plays a very important role, but beyond this I really do not know enough about this to have an opinion on this matter. All I can really say is that more research needs to be done, and that I’m surprised that virtually none of these elite east African runners is a joggler.

In the mean time, some experts have tried to answer this question. Here are some interesting studies that look into this:

Kenyan and Ethiopian distance runners: what makes them so good?

Kenyan dominance in distance running.

Aerobic exercise capacity at sea level and at altitude in Kenyan boys, junior and senior runners compared with Scandinavian runners.

Mitochondrial haplogroups associated with elite Kenyan athlete status.