This rings some bells in my head.
Obviously, white, black, and asian are the dominant 'races' ... but there is I personally have no idea why the skin colour gene determines a person's 'race'.
but what rung in my head was that some tribal people in north-western china were fuond with chinese looks but they were all tall (for east asians), like 6'0 +, with other european traits, and apparently it was because they had mixed with europeans in the past. and apparently they found asians with blue eyes, but im not sure i believe that because i think the brown allele is dominant