Image: Asianic migration routes of the Native Americans. 

The introduction to the Book of Mormon:[footnote]Introduction to the Book of Mormon – LDS.org [/footnote]

The book was written by many ancient prophets by the spirit of prophecy and revelation. Their words, written on gold plates, were quoted and abridged by a prophet-historian named Mormon. The record gives an account of two great civilizations. One came from Jerusalem in 600 B.C. and afterward separated into two nations, known as the Nephites and the Lamanites. The other came much earlier when the Lord confounded the tongues at the Tower of Babel. This group is known as the Jaredites. After thousands of years, all were destroyed except the Lamanites, and they are the principal ancestors of the American Indians.

In 2006, after DNA studies began confirming Asianic migration rather than Middle Easter migration the text was changed to read:[footnote]Single word change in Book of Mormon speaks volumes – Salt Lake Tribune [/footnote]

The book was written by many ancient prophets by the spirit of prophecy and revelation. Their words, written on gold plates, were quoted and abridged by a prophet-historian named Mormon. The record gives an account of two great civilizations. One came from Jerusalem in 600 B.C. and afterward separated into two nations, known as the Nephites and the Lamanites. The other came much earlier when the Lord confounded the tongues at the Tower of Babel. This group is known as the Jaredites. After thousands of years, all were destroyed except the Lamanites, and they are among the ancestors of the American Indians.

Crash Course:

Single word change in Book of Mormon speaks volumes – Salt Lake Tribune
A genomic view of the peopling of the Americas – Harvard University
Book of Mormon and DNA Studies – Gospel Topic Essay
Simon Southerton, DNA, Lamanites and the Book of Mormon (podcast) – Mormon Stories