From Science 30 July 2004:
Vol. 305. no. 5684, pp. 637 - 639
Various studies have shown that West African athletes have denser bones, less body fat, narrower hips, thicker thighs, longer legs, and lighter calves than whites. But the differences between East and West Africans are even more striking. The fabled Kenyan runners are small, thin, and tend to weigh between 50 and 60 kilograms, whereas West African athletes are taller and a good 30 kilograms heavier, says Timothy Noakes, a prominent exercise physiologist and researcher at the University of Cape Town.
The differences don’t stop with body shape; there is also evidence of a difference in the types of muscle fibers that predominate. Scientists have divided skeletal muscles into two basic groups depending on their contractile speed: type I, or slow-twitch muscles, and type II, fast-twitch muscles. There are two kinds of the latter: type IIa, intermediate between fast and slow; and type IIb, which are superfast-twitch. Endurance runners tend to have mostly type I fibers, which have denser capillary networks and are packed with more mitochondria. Sprinters, on the other hand, have mostly type II fibers, which hold lots of sugar as well as enzymes that burn fuel in the absence of oxygen. In the 1980s, Claude Bouchard’s team at Quebec’s Laval University took needle biopsies from the thigh muscles of white French Canadian and black West African students. They found that the Africans averaged significantly more fast-twitch muscle fibers—67.5%—than the French Canadians, who averaged 59%.
Endurance runners have up to 90% or more slow-twitch fibers, Saltin reports. Bouchard, now at Louisiana State University in Baton Rouge, says his team looked at two enzymes that are markers for oxidative metabolism and found higher activity of both in the West Africans, meaning they could generate more ATP, the energy currency of the cell, in the absence of oxygen. The study suggests that in West Africa there may be a larger pool of people “with elevated levels of what it takes to perform anaerobically at very high power output,” says Bouchard.
Although training can transform superfast-twitch type IIb fibers into the hybrid type IIa, it is unlikely to cause slow- and fast-twitch fibers to exchange identities. Myburgh says there is evidence that, with extremely intensive long-distance training, fast IIa fibers can change to slow type I fibers. So far, however, there is no evidence that slow-twitch fibers can be turned into fast-twitch ones. As an athlete puts on muscle mass through training, new fibers are not created, but existing fibers become bigger.
Black male athletes have 26% more muscle viscosity than white male athletes. Black females have 45% greater muscle viscosity than white female athletes(Farley & Gonzalez 1996)
West African sprinters have lower shank inertia in which would allow them to spend less energy on moving their limbs (Rahmani 2004).
Senegalese sprinters were less strong and less powerful at high speeds in a squat movement compared to Italian sprinters of the same 100-m times although muscle abilities involved in slow maximal contractions were similar(Rahmani 2004).
Your digging a big hole Sir 
Any Olympic & WC sprint champions come directly from West Africa nations?
Yep. Nigeria and Namibia 
(probably some others, but I forget off the top of my head). If we extend it to those who have gone under 10/20 seconds as opposed to just those that are world or Olympic champions, the list becomes significantly larger.
And if you include countries that are made up of predominantly West Africans… well you get the picture.
The fact that the country of China with over a billion people and TONS of great facilities, state sponsorship, etc. (or the Soviet Union at its “peak”) can’t/couldn’t muster up a single athlete male 100m athlete that could compete with St. Kitts & Nevis, the Netherlands Antilles, Barbados, Trinidad and Tobago, Namibia, the Bahamas, and numerous other countries kind of hurts your argument here.