Well depends on what you mean a race which is a social concept at best. You have flat hair, round hair, eye fold, sans fold, high melanin, low melanin, thin nose, thick nose alleles (there are ear shapes too, but oddly nobody counts them as part of your racial Identity short of vulcans and elves). This is a genetic Mr. potato head.
Anyone in the sun cancer belt will eventually get darker skin. Because skin cancer will kill you relatively quickly. The rest are just luck of the draw from when ever humans split. None of them are linked to each other. You can be black with blond hair, Asian with green eyes. If you don't have a culture behind it to say "we are the green eyed Asian people" people assume it is a novelty and move on. Remember humans are smart and can make anything part of sexual attraction. People with these traits are gobbled up quickly, taken care of better, and live better. Who thought small feet were sexy enough to break women?s feet in foot binding, or small waist sexy enough to push your ribs into your liver and make child birth impossible. It also works in reverse by making something obnoxious a cultural trait to keep outsiders from mixing with you.
You said the process magically stopped 1 AD. I know there are a bunch of Mexicans that will disagree with you. Almost 500 years ago lil white guys in boats met some Indians and now you have a whole new "race".