Orson Pratt offers premortal explanation of race and ban.
Orson Pratt, "The Pre-Existence of Man," The Seer, 1, no. 4 (April 1853), 56
Some spirits take bodies in the lineage of the chosen seed, through whom of the chosen seed, through whom the priesthood is transferred. others receive bodies among the African negroes or in the lineage of Canaan whose descendants were cursed, pertaining to the priesthood. Now if all the spirits were equally faithful in the first estate in keeping the laws thereof, why are they placed in such dissimilar circumstances in their second estate?