"When asked why they were so dominant, he answered "because they have never even seen a kettlebell""
Haha, no doubt true, but this discussion is interesting on many levels.
Despite the comment that "you can be anything you want", there is no real evidence this is true. Top Kenyan runners have many in-born traits that seem to give them an advantage. They have smaller legs=less weight to move. They use oxygen more efficiently. They have a much higher proportion of type I muscle fiber. They have a higher incident of a gene which is associated with less muscle, less fluid retention, and more relaxed blood vessels—which would enhance oxygen uptake—and appears to be more prevalent in endurance runners in general.
As to converting from type I to type II fibers, there really isn't much evidence for this either. The best studies to date show that identical twins have pretty much identical proportions of each fiber type, even if one of them is a couch potato and the other trains hard. But all the science obscures the fact that, whatever fiber composition you are born with, you can definitely improve on either strength or endurance through training. The training leads to increased blood flow to the muscles you use, and increased mitochondria. All this makes the muscles you are born with more efficient. Keep in mind that the range of type I muscle found in the population ranges from 5-90%, but most of us fall somewhere in the middle, with an average of 45-60%. Also keep in mind that a subtype of type II fibers CAN actually work either way. Type IIa can be recruited for aerobic or glycolytic metabolism. So how much of this type you are born with can also influence how versatile an athlete you can be. The last thing to keep in mind is that the study of muscle fibers changing with training is still a very murky field of research. It traditionally relies on small muscle biopsies of a specific muscle (usually thigh), and there is a lot of error in interpreting this data because it doesn't look at whole fibers, just small cross sections in one muscle. There seems to be different distribution of fibers in other muscles within the same individual, so they may have better upper body endurance or strength than reflected in the leg biopsies. I expect to see an explosion of research in this area in the near future, as new MRI imaging methods will allow researchers to look at whole muscle, and many muscles, without the limitations of invasive biopsies.
The take-home message is, you cannot be anything you want to be, but there is a lot of room for improvement in using what you are born with. Sure, you may never beat a Kenyan runner in a marathon, and for sure you won't see many Kenyans excelling in explosive power sports, but you can improve on yourself, in either or both directions.