Although farming of any sort was almost as impossible in the plains as in the dry regions of winter rains farther west, the abundance of buffaloes made life much easier in many respects.
In fact, the history of North America has been perhaps more profoundly influenced by man's inheritance from his past homes than by the physical features of his present home.
Man could not stay there forever. He was bound to spread to new regions, partly because of his innate migratory tendency and partly because of Nature's stern urgency.
The evidence points to central Asia as man's original home, for the general movement of human migrations has been outward from that region and not inward.
Again and again, to be sure, on the way to America, and under many other circumstances, man has passed through the most adverse climates and has survived, but he has flourished and waxed strong only in certain zones.
For the source of any characteristic so widespread and uniform as this adaptation to environment we must go back to the very beginning of the human race.
Geologists are rapidly becoming convinced that the mammals spread from their central Asian point of origin largely because of great variations in climate.
The human organism inherits so delicate an adjustment to climate that, in spite of man's boasted ability to live anywhere, the strain of the frozen North eliminates the more nervous and active types of mind.
Today, no less than in the past, the tetrahedral form of the earth and the relation of the tetrahedron to the poles and to the equator preserve the conditions that favor rapid evolution.
