Races are not biologically real. But they are socially real.
Race is a system for rapid visual classification. Race is Face.
Race is used to assign people their "correct" social place; a shorthand for telling what sorts of behavior is appropriate for what sorts of people.
Next: Race is caste
Optional link. Check out The Race Project, a website sponsored by the American Anthropological Association.
Optional Link. Check out The Brotherhood of Man, a cartoon from 1945 by Ring Lardner Jr based on the work of Boas' students Ruth Benedict and Gene Weltfish. An interesting historical, historical anthropological look. If you watch this, keep in mind that it's 70+ years old. Today, the language, and some of the thinking has changed. There are several things they get wrong and, of course, it's simplistic (it is a cartoon after all). However, it's pretty amazing how much they got right.