Other men seem to have chosen to tramp and hunt eastward and northeastward from the strait. In this direction there were two main routes open to men and game. One route led up the narrow lowlands of the northwest coast to the mouth of the Mackenzie River and then south up its long valley. The other, and much more likely path for early man, was up the ice-free Yukon and its tributaries. These would have taken him eastward to the Mackenzie or southward through the plateau between the northern Rockies and the Coastal Range. Hrdlička thought the Yukon valley a most unpromising route because of the turbulent rivers and the noxious insects; but most students disagree with him and stress the abundance of fish and game. There can be no question that some parts of this route were used by early man—and extinct mammals, too. His ancient spear points have been found in the muck beds of Fairbanks mingled with the fossilized bones of elephant, bison, camel, horse, and an extinct jaguar once called the Alaskan lion.[14] Other early points have been discovered in western Canada in the area of the mountain plateau. In 1944 Frederick Johnson located fifteen camp sites in early soil levels along the route of the plateau corridor and found many varieties of artifacts. Among these were a few points, most of them fragmentary, the butts of which resembled those of an early type.[15] Following Johnson in 1945, Douglas Leechman found other sites and artifacts along this route in soils formed perhaps 9,000 years ago.[16]
The Yukon valley rivers could have taken early man to the Mackenzie and to the northern edge of the plateau; but during a large part of the Great Ice Age he still faced the gigantic fields of snow and ice that covered half of North America. Although ice journeys may not be so very difficult, and early man had learned to live in the chill of northern Siberia (the Eskimo of today proves that human existence is possible in a land of little sun and much cold), we cannot believe that he attempted to cross the icy wastes. A journey on foot across a thousand or two thousand miles of ice becomes a sheer impossibility if there is no provender to be found along the way. There was certainly no food for musk ox or mammoth, and therefore no food for man. Without game to hunt, he would not have felt the impulse to invade the ice fields.