Mark of Cain

The Mark of Cain is an old American Christian belief-cum-serving-of-eugenicist-woo that forms the foundation of American religious-based racism and also, subtly, the entire creationist movement.

Premise
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A literal reading of this passage could be easily interpreted as a science-fictional idea where a certain segment of humanity descended from the lineage of Cain would be cursed with an aberration in skin pigmentation. Even though the mark would likely have been superficial to identify Cain himself for what he had done, and therefore would not have been inheritable, since Lamarckism doesn't work.

Execution
The weak attempt to preserve antebellum racism in America worked because Southern Protestant preachers said they read the Bible in a way that included a teaching wherein blacks were inferior due to a descent from Cain's brood. As such, it was a basic violation of the First Amendment to restrict exercise of religiously-approved doctrines regarding interactions with African Americans. The Southern Democrats were apt to maintain social order and be seen as quasi-religious by not challenging these precepts. The Southern Baptist Convention did not formally renounce its racist past until 1995.

Modern iterations in creationism
The hinge of the creationist movement is that human beings are divinely created by God. However, considering this level of literalism in their doctrine, it is easy to see how this view also extends to the later chapters on Genesis. It may not come up a lot, but if they believe in Noah's Ark and the Exodus, they probably have to, by default, accept this view. As such, according to creationists, Cain-ites would still walk the Earth marked as a cursed line, damned for eternity to the seven deadly sins. The fact that the creationists also tend to be pro-austerity fiscal policy advocates who use blatant and obnoxious stereotypes about welfare queens and dangerous black men gives this theory further credence.

Mormons
The Mark of Cain theology was most blatant in the teachings of Brigham Young, leader of the Mormon religious movement after Joseph Smith. Young tied the Mark with the Curse of Ham, claiming in the Book of Abraham that Ham's wife was a descendant of Cain. The Lord said I will not kill Cain, but I will put a mark upon him and it is seen in the face of every Negro on the earth, and it is the decree of God that that mark shall remain upon the seed of Cain and the curse until all the seed of Abel should be redeemed and Cain will not receive the Priesthood or salvation until all the seed of Abel are redeemed. Any man having one drop of the seed of Cain in him cannot hold the Priesthood, and if no other prophet ever spake it before I will say it now in the name of Jesus Christ. It was only in 1978 that the President, Prophet, and Seer had a vision that said they should allow black Mormons full participation in the faith. However, ceremonials for the Church still maintain the idea of the Mark of Cain. Now they believe, however, that a prayer and blessing can remove the curse upon baptism into the Church. They no longer believe that removal of the curse will result in Black people becoming white.