"Mark" on Cain

As I was reading in genesis, I read the verse Genesis chapter 4, verse 15 which says,

"And the Lord said unto him, Therefore whosoever slayeth Cain, vengance shall be taken on him sevenfold. And the Lord set a mark upon Cain, lest any finding him should kill him.

In the Book of Mormon it mentions in Alma 3, verses 6-8, 

 "And the skins of the Lamanites were dark, according to the mark which was set upon their fathers, which was a ^acurse upon them because of their transgression and their rebellion against their brethren, who consisted of Nephi, Jacob, and Joseph, and Sam, who were just and holy men."

 "And their brethren sought to destroy them, therefore they were cursed; and the Lord God set a ^amark upon them, yea, upon Laman and Lemuel, and also the sons of Ishmael, and Ishmaelitish women."

 "And this was done that their seed might be distinguished from the seed of their brethren, that thereby the Lord God might preserve his people, that they might not ^amix and believe in incorrect ^btraditions which would prove their destruction."

You can see how this mark talked about in Genesis is mentioned how it is "dark, according to the mark", and how it is a "curse". God put this mark to protect "his people" that they might not mix. 

Event thought there are theories of African Americans that has been heard before, According to the Churchofjesuschrist.org "Today, the Church disavows the theories advanced in the past that black skin is a sign of divine disfavor or curse, or that it reflects unrighteous actions in a premortal life; that mixed-race marriages are a sin; or that blacks or people of any other race or ethnicity are inferior in any way to anyone else."

I think of how something from the past could be different in meaning then something of the present to others whether it is looks or any other sign, mark, or anythings different, unique, ect. God can place meaning on something that is different in its representation to a people or timeframe then it is to other time frames or people. I am thankful for modern inspiration that guides people in following god and clarifies doctrine.