That's a way to deal with the problems generated by apparent conflict between science and one's holy book: just get the holy book changed a little.
P. S. One Brow is quite right, of course. The change is to the introduction, written in the 1980s. A more interesting question concerns what this does to the historic mission of the Mormon church. Historically, this has involved a special mission to Native Americans on grounds that they are Lamanites, that is, descendants of the Book of Mormon peoples. At one time this was the basis for an adoption program of Native Americans into Mormon households, and past President Spencer Kimball is notorious for having said that the program must be working because you can see the effects of greater righteousness in these adoptees by seeing that their skin has gotten whiter in the course of their adoption to those Mormon households. If Mormons stop believing that the people who live on the res are Lamanites, doesn't that entail that one of the Mormon Church's primary missions has been misguided all these years?
Another interesting question is whether the Prophet, Seer and Revelator (aka the President) of the Mormon Church could change the text of the book of Mormon if the PSR were to claims fresh revelation as a basis for doing so. Given a belief not only in modern revelation but also in ongoing revelation, this would be more to be expected coming from Mormonism than it would be coming from either Catholic or Protestant Christianity.