That's a weak counter argument. Natural selection happens only when things happen on a grand scale. Like during wars. Africans generally have better vision than many other ethnic groups, but there are no vision olympics.
Jamaica is more dominant for cultural reasons - the people there are more likely to have the opportunity to train for the olympics than in West Africa.
How do you want to account for Natural Selection then? There are no animals left in the world which are capable of killing humans in quantities that would favour one trend over the other. There is no disease that selects for Speed. There is only one predator that can cause the natural selection for speed among humans - and that is other human beings!
West Africans are distinct from other African groups when it comes to genetic specialisation - take a look at the wikipedia page on sickle cell anemia for example. Also take a look at language families as some data to cross reference with.
My evidence is speculatory, but it's realistic, I believe. My reasoning is however logical.
I am not so sure it is logical. Obviously groups of people have genetic differences. Sickle cell anemia is a great example, here we have exactly one gene which gives malaria resistance with one copy and immunity and anemia with two. And endemic malaria is one hell of a natural selector.
But suppose I claimed that the long standing domination of Romanian gymnasts was genetic. And then I came up an elaborate explanation involving contests of balance and bouncing set to music that decide which maiden gets to marry. Strictly speaking a logical theory but not very smart.
Cultural reasons are a huge contributor, just look at the Russian relay team and their baton passing skills.
Then there's simple genetic drift and founders effect. Those are most often responsible for genetic differences. The Ashkenazi are descendant from a VERY small group of founders. What is a very rare genetic mutation, by accident became common in the Ashkenazi population.
That's simple genetics, but natural selection is much more complicated. The Jamaicans might have more fast twitch muscle fiber due to natural selection, or they might have it because of a genetic bottle neck in the slave trade.
The few Africans who got to Jamaica first happened to have rare genes and there you go founders effect. Or it just might be all cultural with no genetics.
The elaborate scenario with villages and night time warfare and running (but no moats?) is only slightly more serious then any scenario involving music coordinated gymnastics based natural selection in Romania.
Jamaica is more dominant for cultural reasons - the people there are more likely to have the opportunity to train for the olympics than in West Africa.
How do you want to account for Natural Selection then? There are no animals left in the world which are capable of killing humans in quantities that would favour one trend over the other. There is no disease that selects for Speed. There is only one predator that can cause the natural selection for speed among humans - and that is other human beings!
West Africans are distinct from other African groups when it comes to genetic specialisation - take a look at the wikipedia page on sickle cell anemia for example. Also take a look at language families as some data to cross reference with.
My evidence is speculatory, but it's realistic, I believe. My reasoning is however logical.