Why English speakers dominate sprinting events

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.

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.

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.

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.

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.

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.

Contrast this with East Africa, where the savannag lead to Bows & Arrows and Spears being used as war weapons.

Maybe there were faster, scarier predators around in that area.

"Runners of West African descent—which includes Jamaicans as well as most African-Americans—seem to be built for speed: In 2004, they held all but five of the 500 best times in the 100-meter dash. (East Africans, such as Kenyans and Ethiopians, rule the long-distance field.) Several biological factors may be coming into play here. One study conducted in Quebec in the 1980s found that black West African students had significantly higher amounts of "fast-twitch" muscle fibers—the kind that are responsible for short, explosive bursts of action—than white French Canadians did. (So far, there is no evidence that even extensive training can turn slow-twitch muscles into fast-twitch ones, though moving in the other direction is possible.)"

http://www.slate.com/id/2197721/