The problem is only that there are not discrete categories. For starters, how do you classify children of parents belonging to two discrete racial groups? And their children? And so on and so forth. Well, people have been spreading their genes around the globe for a long time, and the upshot is we all belong to the same racial group. Sure, there are clusters, but there are not purebreeds.
Further, culture / ethnicity is just a much more accurate way to classify people than genotype or phenotype. I don't have a source for this, but I believe the best way anthropologists have come up with to group people is by the kind of food they eat.
Further, culture / ethnicity is just a much more accurate way to classify people than genotype or phenotype. I don't have a source for this, but I believe the best way anthropologists have come up with to group people is by the kind of food they eat.