Not more than transient and arbitrary ones, no. Less so than putting green eyed and blue eyed people in separate categories, since there are so many people that don’t share the supposed physical characteristics of the “race” they belong to. There are plenty of pale “black people”, for example.
Because their parents consider themselves black or white not because of some biological reason. “Black” isn’t a skin color; there are “whites” darker than some “blacks”. It’s a social category. We call people “black” because some of their ancestors are known to have came from Africa and we still tend to hold to the old racist standard of treating “white” as purity and “black” as contamination. If you’ve got a little bit of “black blood” in you you’re contaminated and not “white”, while the guy who has more “white” ancestors than “black” still doesn’t count as “white”.
It’s a combination of leftover racism and essentialism; treating things as if they had some kind of unalterable essence. It’s treating “black” or “white” people as parts of groups not because they are actually genetically similar to each other but because they have some sort of mystic essence passed down generation by generation that can’t ever change. Very common among conservatives, who freak out over the idea that such near categories aren’t absolutes, that species can change or that people aren’t always neatly, innately “male” and “female” or “black” and “white”.
