I think I found the problem! the Professor is confusing race with species! For his edification, race is a subset of species. This means not that some of us do not come from African descendants. It simply means that those “groupings of shared characteristics” in different regions are more the rule than the exception.
I’m not “confusing” race with species. I’m pointing out that “race” is a subjective and scientifically vacuous criterion for discriminating between different human individuals. I think the following exercises will help illustrate the problems with making “racial” distinctions based on superficial differences.