While some of the artifacts herein enumerated and described were undoubtedly made by Sioux and Mandan Indians, it appears quite certain that the products of the mound burial-pits, that is, the spirally grooved urns, the tubular pipes, antler tynes, and sea-shell ornaments, belonged to some other ancient tribe, possibly to the ancient Arikaras, or to a yet earlier tribe. CHAPTER XXXVI CONCLUSIONS Naturally, the Conclusions to “The Stone Age” are somewhat long, and while I have embodied them all under two chapters, yet they have been grouped under subdivisions, as will be observed by readers. THE POPULATION IN PREHISTORIC TIMES We should first consider a subject which has been given, it would seem, scant attention. I refer to the fact that generally throughout the American continent are unmistakable evidences of a considerable population in ancient times. At present there are about three hundred and sixty thousand Indians in the United States and Canada. Perhaps more than half of these show the effects of marriage with whites or negroes. The population of to-day is no criterion of that in ancient times. In studying field evidence of population, we must bear in mind that the Indian of both periods made use of perishable materials. This is an essential fact to be noted during the course of our studies. Much that both the historic and prehistoric Indian made use of was composed of cloth, iron, wood, brass, leather, etc. It is quite true that the wood, leather, cloth, etc., of prehistoric times would disappear, but the stone, bone, shell, clay, and copper objects remained. Iron rusts quickly, and the use of iron was widespread from the time of the settlement on the New England coast (1620) down to the present. A great deal of iron was introduced by De Soto in Florida, South Carolina, Georgia, Alabama, Arkansas; and by Coronado in the Southwest. Both of these expeditions were in the years 1540–1543, and on them hundreds of Spaniards penetrated into the interior carrying thousands of objects, chiefly of iron. All of this must have had an effect on the natives throughout a considerable portion of North America. I have elsewhere referred to the difference between historic and modern sites, but the subject is important and has been, it seems to me, passed over or not appreciated by others, and it is necessary to emphasize the difference between the ancient and the modern again. The significant fact is that all of this iron has disappeared leaving here and there a streak of rust, and that upon the modern sites were left quantities of glass beads and other objects that are not perishable. These were in use among the natives, yet few of these things remain; the only exception being noted in the sites of the Iroquois of western New York, where the modern artifacts predominate.