why the lamanites' skin was dark

[Dan]

Remember the depiction of Enos in his lone chapter:

20 And I bear record that the people of Nephi did seek diligently to restore the Lamanites unto the true faith in God. But our labors were vain; their hatred was fixed, and they were led by their evil nature that they became wild, and ferocious, and a blood-thirsty people, full of idolatry and filthiness; feeding upon beasts of prey; dwelling in tents, and wandering about in the wilderness with a short skin girdle about their loins and their heads shaven; and their skill was in the bow, and in the cimeter, and the ax. And many of them did eat nothing save it was raw meat; and they were continually seeking to destroy us.

I have always wondered just how literally I should believe that statement.