These ancient tribes seemed to have lived, each in its nook of coast or river valley, for unnumbered ages, never going to see what was on the other side of the mountain, each developing its own morsel of civilization in its own way, its life and culture and development modified by the portion of the earth's surface where it sat down, seemingly to stay forever. Shell heaps were found miles in length, with tree stumps six feet in diameter standing on nine feet of layers, of which each layer was only an inch or two in thickness. It took a good many generations to pile up those successive layers with discards from shellfish dinners. A stump of Douglas fir, over six feet in diameter, stood on a shell heap eight feet below the surface which contained human remains. The tree indicated the top layers of the shell heap were more than 500 years old.