Alma 2:11; refer in this text to 2 Ne. 5:21-23; Jacob 1:13-14; Hel. 11:24
“Here God places his mark on people as a curse, yet it is an artificial mark which they actually place upon themselves. The mark was not a racial thing but was acquired by ‘whosoever suffered himself to be led away by the Lamanites’ (Alma 3:10); Alma moreover defines a Nephite as anyone observing ‘the traditions of their fathers… .’ (Alma 3:11). Which makes the difference between Nephite and Lamanite a cultural, not a racial, one… . The cultural picture may not be the whole story of the dark skin of the Lamanites, but it is an important part of that story and is given great emphasis by the Book of Mormon itself.” (Hugh Nibley, Lehi in the Desert, p. 85)
“Originally, the Lamanites were the children of Laman, Lemuel, and some of the family of Ishmael; but as the centuries passed there were many defections in both nations, when the dissatisfied would join the opposing race and affiliate and intermix with them, so that the two names at last became more an indication of religion and civilization than of birth.” (George Reynolds, A Complete Concordance of the Book of Mormon, p. 395)
“It should be noted that the Lamanites were often absorbed by, and were called Nephites when they were righteous, and it is true also that the Nephites when they rebelled and became wicked, were often times called Lamanites, and there was undoubtedly a considerable mixture among them.” (Spencer W. Kimball, Conference Report, Apr. 1949, p. 107)