It probably is silly, Kendall, as I implied in my caveat at end of my post; but I think it probable that they were not conscious conservationists either. They lived on, & off, the land, without probably thinking too much about the morality of the matter but just to keep going. The 'herd over a cliff' hyperbole is probably mythical, but I expect they killed more bison than they actually required for immediate dietary need. Many tribes were, culturally, hunting people, after all.

~M~