Taken all together, therefore, the conditions described provided man with a chilly but relatively dry and passable route from the Asiatic mainland to Alaska and thence to the warmer interior sections of North America. For a considerable period this route must have been flanked with glacial ice lying only a few miles away on one side or both through a total distance of some 2,000 miles. It is one of man’s distinctive qualities, however, that he is able to adapt himself to extremes; and it is probable that the game he lived on was itself acclimated to living close to the edges of the ice sheets. We are less certain about the conditions under which this journey was begun at its Asiatic end; but it seems likely that there, too, ice would have formed in the high mountain masses, but that the valleys and lowland would have remained open as they did farther east. We are confident in our knowledge of where man came from to the New World and how he was able to make the trip. We are on less certain ground, however, when we try to determine when he arrived. Estimates have varied widely, changing with every increase in our knowledge. From the first enthusiastic attempts to fit the Indian into the Old Stone Age chronology which was just then unfolding for the Old World, the cold reasoning of skeptical scientists brought down the maximum age of human occupation of this hemisphere to something like 3,000 years. Beginning in 1925, however, a series of finds has provided unquestionable evidence that men using very distinctive weapons were living on this continent, largely by hunting the mammoth and a great bison, both now extinct, during the period when the ice was receding for the last time. The typical channeled or fluted spear point of this people has even been found lately along the northern Alaska coast. So, while we still cannot say that this characteristic artifact was brought from Asia rather than being developed here in America, it is at least an interesting coincidence that man hunted large and now extinct game in Alaska in areas where conditions were at times particularly well suited to his immigration.