Nephi sees the history of the Lamanites and Nephites. Therefore, Nephi knew from very early on, that there would be a permanent division in the family. So far he has learned that his brothers are not going to partake of the tree of life. Now he will learn that the seed of his brothers will have many wars with his descendants. In addition, he sees the land of promise years before arriving there.
Many experts have tried to figure out how large the population was in Book of Mormon times. Nephi describes it as "in number as the sand of the sea." Expert predictions may understimate the number of people who lived on this continent. Evidence suggests that near the time of Christ, the settlements were not great in number, and the geography was confined to a relatively small area. However, latter-day attempts to shrink the geography populations of the Book of Mormon have at times gone too far. Nothing can be determined about the number of people who lived in the Jaredite era or during the many generations which passed between Nephi and king Benjamin. We must accept the fact that the Book of Mormon was not written as a census or an almanac. But the population seemed to Nephi 'as the sand of the sea' for multitude.