Interbreeding with what?
Humans spread out over the world, probably from Africa where they were dark. As time went on they grew lighter in the northern areas.
Maybe after the races were formed there was interbreeding, but prior to that it was evolution. You can't have "interbreeding" if everything is the same.
The same thought is true when the literalists claim three races came immediately from the same family.
Good point. I was actually trying to, for the sake of argument, concede that interbreeding caused skin color variations, but that this was irrelevant to whether or not allele frequencies had changed.