Minutes of the Council of the Twelve and of the First Presidency: Letter from lra N. Hinckley read, stating that a man in Oasis named Church had received his patriarchal blessing in which he was told that he was of the lineage of Ephraim and that he should receive the priesthood and go on a mission But it is understood that he inherits some negro blood in him through his mother, and questions were being asked about the right of this party to hold the priesthood, some holding that he might do so provided the white blood predominates.
President [Lorenzo] Snow, commenting on this subject, said that he asked President Brigham Young on one occasion why it was that millions and millions of people were cursed with a black skin, and when, if ever, this curse would be re-moved? President Young explained it to him in this way, but whether the President had had this revealed to him or not he did not know, or whether he was giving his own personal views of what had been told him by the Prophet Joseph [Smith]. He said that when Cain slew Abel he fully understood that the effects would not end with the killing of his brother, but that it extended to the spirits in eternity. He said that in the spirit world people were organized as they are here. There were patriarchs standing at the head of certain classes of spirits, and there were certain relationships existing which affected their coming into the world to take tabernacles; as, for instance, when Abel came into the world it was understood by Cain that the class of people he presided over as a prince, if they ever came into the world in the regular way, they would have come thru him. So with Cain, he was a prince presiding over a vast number of a certain class of spirits, and it was natural that they should come through him, if at all, and therefore when Cain slew Abel he understood that the taking of his brother's life was going to deprive the spirits over whom he presided from coming into the world, perhaps for thousands and thousands of years; hence the sin was immense because the effects were immense. Then there was this understanding when the Lord executed judgement upon Cain; the spirits under his leadership still looked up to him, and rather than forsake him they were willing to bear his burdens and share the penalty imposed upon him. This was understood when the curse was pronounced upon him, and it was understood that this curse would remain upon his posterity until the class of spirits presided over by Abel should have the privilege of coming into the world and taking tabernacles, and then the curse would be removed.
President [George Q.] Cannon remarked upon this subject, as he said, he had on a prior occasion when this subject was under consideration, that he had understood that the Prophet Joseph [Smith] had said during this lifetime, that there would be a great wrong perpetrated if the seed of Cain were allowed to have the Priesthood before Abel should have posterity to receive it, and this curse therefore was to remain upon the seed of Cain until the time should come that Abel should have posterity. He understood that that time could not come until Abel should beget spirits in the eternal worlds and those spirits obtain tabernacles; if it were otherwise the slayer would have advantage over the slain. President Cannon further remarked that it would seem that there was a class of spirits who had to take such bodies for the reason that Ham introduced this blood through the ark by marrying a woman of the accused seed named Egyptus.
[George Albert Smith Papers, Manuscripts Division, Marriott Library, University of Utah, in Marquardt, H. Michael, Mormon Central: Excerpts From Minutes of the Council of the Twelve and of the First Presidency, 1879-1947 http://www.xmission.com/~research/central/chorg2.htm]