Some passages in Mormon scripture (e.g. Abraham 3:22-23) seem to infer that our mortal station has been influenced to some degree by our valiance-quotient in the pre-mortal sphere. My own patriarchal blessing, for example, states that I was born into the LDS covenant by virtue of my status as a “strong leader” in the pre-existence. Such beliefs are not uncommon in the modern church.
Some Mormon authorities have in the past extended this belief to explain questions of race, i.e. that those held to be “cursed with a black skin” were so marked by God as a caste apart from the rights of the priesthood and that they lived under this curse because of their lack of valiance in the pre-Earth life.
The priesthood segregation of blacks in the Church of Jesus Christ of Latter-day Saints ended in 1978. The teaching of pre-mortal curses receives no official sanction today although, as stated above, the notion of mortal reward for pre-mortal faithfulness continues. Much of the curse folklore appears to have been a speculative attempt to explain the priesthood ban on blacks. In this regard, it is worth remembering the words of Elder McConkie in 1978:
Forget everything that I have said, or what President Brigham Young or President George Q. Cannon or whomsoever has said in days past that is contrary to the present revelation. We spoke with a limited understanding and without the light and knowledge that now has come into the world….
While the Gospel still entertains a belief in degrees of pre-mortal righteousness, there is no indication that this manifests itself with regard to race, class, nationality, or caste. Regarding notions of caste, it is true that ancient “Israel was chosen as a peculiar people, one set apart from all other nations (Ex. 19:5-6; Deut. 7:6; 14:2) and [that] they were forbidden to marry outside their own caste (Ex. 34:10-17; Deut. 7:1-5)” (Mormon Doctrine, s.v. “Caste Systems”); however, Christ brought a new law, one expressed beautifully by Paul:
There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus. (Gal. 3: 28)
Historically, caste systems have been vehicles of social and spiritual damnation. By contrast, the Gospel offers equal opportunity for all to come unto Christ and be saved.
However, all that said, this remains a knotty issue for Mormons. If birth into the LDS covenant within a loving, prosperous family is held to be a reward for pre-mortal goodness (cf. my patriarchal blessing, surely not an outlier), what implications does that have for those born into God-awful conditions? Does Mormonism have a coherent explanation for mortal inequities? It seems we remain happy to pick-up one end of the stick, but what of the other?
 Also, Elder Holland: “One clear-cut position is that the folklore must never be perpetuated.”
 “Discriminatory and cruel, inhuman, and degrading treatment of a vast global population has been justified on the basis of caste. In much of Asia and parts of Africa, caste is the basis for the definition and exclusion of distinct population groups by reason of their descent. Over 250 million people worldwide continue to suffer under what is often a hidden apartheid of segregation, modern-day slavery, and other extreme forms of discrimination, exploitation, and violence. Caste imposes enormous obstacles to their full attainment of civil, political, economic, social, and cultural rights” (Human Rights Watch).