They do exist, but they are
not seperate! Very important distinction. Intermarriage has always taken place between those groups, but dominant traits
tend to carry through. That doesn't mean that you can identify someone with the sickle cell gene as 'African' or 'Black' or any other racial term. There is no one race that carries the sickle cell gene, there is just a large group of people whose heredity and environment have allowed that gene to flourish in their line. There are many, many individuals born of that line who do not carry the gene, and there is no visible, 'racial' method of distinguishing them from any other members of the line.
If race were a genetic referral term in common useage, which dictionary definitions make clear it is not, that would be a somewhat satisfactory use of the word. That is not the case, however, and your own frequent references to the visible differences between people make it obvious what 'race' is taken to mean; the white, black, blond, brown, yellow, etc. There is no connection between a genetic use of the word race and a visible differences use of the word race.
None.
Just one more example, from Sudan. The conflict there is self characterized as between Arab descended Sudanese and African descended Sudanese. They regard one (This is a broad generalization of 'they') as seperate races, but the distinctions certainly aren't visible. Line up any hundred randomly selected individuals, strip them of their cultural difference, and the apparent visible differences would not distinguish them from one another. Similarly on genetic grounds they are one people, intermarriage has gone on for so long that there is no ability to seperate eastern Sudanese from western. You could break them along family lines, as I've noted, but so little variation would exist genetically that to try to isolate one group as a race would be absurd.
That's not a unique case either, the same was true in Rwanda where Hutus and Tutsi regarded one another (Generalization alert!) as seperate races, but they were visibly and genetically identical.
To sum up, go back and look at the definition of race I posted. It is not precise enough to be a useful genetic distinction. It cannot be accurately used on the basis of appearance. So what is left for race to mean? Cultural differences? Isn't that what religious and national identity already do?

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