Demographic: Here we have the real demographic problem for the Book of Mormon.
If we presume, as has been traditional, that there were no "others" in the land, this statement makes if very difficult to understand the population dynamics of the Lamanites and Nephites.
Taken at its most traditional interpretation, we would have two divisions coming from Lehi's original colony, and one of those groups uniting with a second set of descendants from Jerusalem. On the Nephite side of the equation we would have half the original Lehites becoming a minority among a larger population of Mulekites, while the Lamanites would be greater than twice the number of the Nephites and Mulekites together. This original Lamanite population would have to have a birth rate (and a survival rate) of probably four times higher than their brother's families to even come close to making these numbers work.
What complicates this picture even more is the Nephite description of the Lamanites (particularly in early periods) as hunter-gatherers and certainly uncivilized. The problem here is that the hunter-gatherer lifestyle is known to be unable to sustain large populations. Large family sizes virtually require sedentary agriculture to provide sufficient food for the larger population. Peoples who rely upon hunting and gathering only tend to exist in small bands, not large cities.
The entire picture is simply impossible - unless we are speaking of populations augmented by those "others" who were in the New World previous to the arrival of the Lehites and Mulekites. Without the "others" in the picture, the descriptions of peoples and actions in the Book of Mormon would violate nearly all known principles of population size to mode of production.