If you're talking about the fact that many African Americans are about 20% European genetically, but many share "hip hop culture" or African American culture, or whatever, that seems somewhat of a contrived point and it's not clear exactly what the point is you're meaning to make.
If your talking about the often vaunted genetic diversity on the continent of Africa, that has no bearing on the existence of clusters of relative genetic similarity around the world we have come to refer to variously as ethnicity, race, population group, etc. In fact that African genetic diversity supports the reality of distinct population groups and ethnicities because it is a bunch of genetic material that other groups don't have.
The very basis for ethnicity/race/population groups is a genomic "alphabet"/string within certain bounds. In considering the global level distinctions between populations it makes no difference the level of genetic diversity in any particular group.
The defining factor is that various groups share traits that no other group does.
Asians and Europeans have stretches of DNA that we've determined through the magic of modern science come from an extinct species of human called Neanderthals. None of these stretches of DNA are found in Africans.
Likewise, Africans have stretches of DNA that come from as yet identified extinct species, these stretches of DNA aren't found in Asians or Europeans.
Then of course there are the myriad other genetic structures that while having origins in the ancestors of all living humans have nonetheless diverged through the process of evolution over the millennia into reliable genetic markers for the various population groups.
And it is true that ethnic groups are defined as well by visual appearance, for example cranium shape and size, nostril diameter, length of nasal bridge, hair color/texture etc. but these things aren't the result of members of your culture gathering around at your birth and molding these things like clay, these things are encoded in genes and what molded their shape into your genes are evolutionary pressures in your ancestral environment.
The point is a very simple one. People who appear similar, or have a similar cultural background (and hence belong to the same "race" in American terms) are often no more similar genetically than two randomly selected members of the population.
If your talking about the often vaunted genetic diversity on the continent of Africa, that has no bearing on the existence of clusters of relative genetic similarity around the world we have come to refer to variously as ethnicity, race, population group, etc. In fact that African genetic diversity supports the reality of distinct population groups and ethnicities because it is a bunch of genetic material that other groups don't have.
The very basis for ethnicity/race/population groups is a genomic "alphabet"/string within certain bounds. In considering the global level distinctions between populations it makes no difference the level of genetic diversity in any particular group.
The defining factor is that various groups share traits that no other group does.
Asians and Europeans have stretches of DNA that we've determined through the magic of modern science come from an extinct species of human called Neanderthals. None of these stretches of DNA are found in Africans.
Likewise, Africans have stretches of DNA that come from as yet identified extinct species, these stretches of DNA aren't found in Asians or Europeans.
Then of course there are the myriad other genetic structures that while having origins in the ancestors of all living humans have nonetheless diverged through the process of evolution over the millennia into reliable genetic markers for the various population groups.
And it is true that ethnic groups are defined as well by visual appearance, for example cranium shape and size, nostril diameter, length of nasal bridge, hair color/texture etc. but these things aren't the result of members of your culture gathering around at your birth and molding these things like clay, these things are encoded in genes and what molded their shape into your genes are evolutionary pressures in your ancestral environment.