Although I suppose the Asian adoptees available, as probably with all races, weren't exactly the pick of their gene pool. Blood runs true, you know - on average.

(Ironically, the perspectives on human heredity generally held in the premodern era are generally more accurate than those taught in modern schools today. The traditional ideas of "blood" were after all consistent with a broad cultural understanding of animal husbandry, and the mechanisms of heredity aren't any different in humans than in pigs.)