Be careful with "undisturbed." It is a relative term. Before the advent of the blessings of European civilization, native Americans were all over our "wilderness." While their impacts were relatively trifling compared to the massive disruptions of recent times, the land was not undisturbed. In some areas, for instance, fires were set in the fall to improve browse for herbivores. I am not sure how pervasive that practice was, but it was practiced here in southern California.