The reason for this: The best sprinters in the world come from West Africa. Say what you want, this is simply true. I'm going to go through a series of logical steps, and I would like you to see if I can get you to agree with my conclusion<p>The biggest time survival of the fittest comes into play is during a war. When a war happens, the people unfit to fight in the war get pruned out of the gene pool.<p>West Africa has a landscape that is different from most of the world - the bush. The bush is what happens when humans live near a jungle - they trim down the trees, and low vegetation tends to grow. In East Africa, you tend to have savannah and grasslands which can be walked through. You cannot walk through a bush.<p>West African wars have tradditionally been fought with machetes. Not with spears, not with guns, not with swords, but with Machetes. A machete is a proximity instrument, and the best way to defeat someone in a machete fight is to be the one to strike first.<p>A west African war looks this way - all the men paint themselves in black, and walk at night through the bushes till they are near a village. A village is usually cleared of grass and bush, so there is no cover. When a whistle is sounded, the men burst out of the bush and run at high speed towards the village, winning the war by force.<p>The men in the village have a few seconds to prepare, and they do so by grabbing their machetes and running as quick as possible away, then circling back.<p>Traditional west African wars are high speed dashes with heavy instruments, in the night, and with lots of fire. It's the perfect enviroment to have gene pool selection for dashes.<p>Contrast this with East Africa, where the savannag lead to Bows & Arrows and Spears being used as war weapons.
I think the answer is somewhat more obvious. Look at the facilities, coaches and funding available for athletes in the USA, Jamaica, and Britain compared to West Africa.
What about doping? Another throwaway idea: racism still exists, so the blacker somebody looks, the more likely they'll have to resort to desperate means like allowing dangerous medical experiments on their bodies (doping) to still have some success in society. (I am not claiming this is the explanation, just want to point out another possible explanation).