So at present the whole question of the age of these bones resolves itself into a statement of one party that they were found in undisturbed loess, as reported; and of the inability of another party to show that there may have been an error of observation or a mistaken interpretation.
There need be no such doubt in regard to the age of the mounds or the lodge sites. It would not take many centuries for mounds upon these sharp, exposed ridges to be entirely washed away, in spite of the fact that the fine loess is almost impermeable. Rain may not reduce them to an appreciable extent, but frost and wind will gradually wear them down. As to the lodge sites, their similarity to modern Indian houses is so pronounced that we are fully justified in attributing them to the same degree of culture as that of the Indians of a century ago. The only point of difference is that the latter dwellings have not such deep excavations, but the incursion of war-like tribes, or the restlessness that impels a primitive community to be frequently on the move, seems a simpler explanation of the difference than to suppose that identical types are separated by a great period of time.
Three points must be taken into consideration in fixing a definite age for these remains:
1. The relics found in and around the lodge sites, except for the markings on some of the pottery, are in no wise different from those picked up on the sites of villages which were occupied when Lewis and Clark came through here.
2. Fairly solid bones of animals, and occasionally of humans, are found in the bottoms of the lodge sites, even where these are damp most of the year. In the pits, where such remains are preserved by ashes, this would not mean much; but where they are found in clayey earth it is evident that "thousands of years" is a meaningless term to apply to them.
3. Persons who claim these "thousands of years" for pretty much everything they find in the ground must explain why it is that while the bones and implements of these assumed "ancients" are found in such quantities and in such good preservation, those of later Indians should have entirely disappeared.
The only tenable theory of age is the amount of accumulation in the depressions of the lodge sites. Above the clay which formed the roof, and is next to the floor now, is a depth of material sometimes (it is said) as much as 20 or even 22 inches of mingled silt, decayed vegetation, and soil from the surrounding wall. It is used as an argument of age that as these sites are on hilltops where there can be no inwash, this depth must indicate a very remote period for their construction. But a large amount of the earth thrown out into the surrounding ring or wall will find its way back into the depression. The water will stand in them a good part of the year, and the soil remain damp even in prolonged drought; vegetation is thus more luxuriant than on the outside, and its decay will fill up rather rapidly. In addition, much sand blows from the prairies as well as from the bottom lands, and whatever finds its way into the pit will stay there; it will not blow away again as it would in open ground. The weeds, also, will catch and retain much of this dust which would pass over a dry surface. Consequently the allowance of an inch in a century, which is the most that advocates of great age will allow for accumulation, is much too small.
The topography of the region was essentially the same when these remains were constructed as it is now. The hills and valleys were as they now exist; the erosion has been very slight as compared with what has taken place since the loess was brought above the water, to which it owes its origin. This statement is fully proven by the position of the mounds and lodge sites. Any estimate of age must be only a guess at the best, but it is a safe guess that no earthwork, mound, lodge site, or human bone along this part of the Missouri River has been here as long as 10 centuries.