Many difficulties present themselves in bringing these periods into correspondence with the seasons of the Quaternary in Europe; but after a careful study of both continents, Mr. W. J. McGee suggests the following synchronisms:[31] _North America._ _Western Europe._ Inter-glacial period Époque chelléenne. Early second glacial period Époque mousterienne. Middle (mild) second glacial period Époque solutréenne. Close of second glacial period and post-glacial Époque magdalénienne. Champlain period Kitchen-middens and epoque Robenhausienne. Of course it would not be correct to suppose that the earliest inhabitants of the continent presented the physical traits which mark the race to-day. Racial peculiarities are slowly developed in certain “areas of characterization,” but once fixed are indelible. Can we discover the whereabouts of the area which impressed upon primitive American man--an immigrant, as we have learned, from another hemisphere--those corporeal changes which set him over against his fellows as an independent race? I believe that it was in the north temperate zone. It is there we find the oldest signs of man’s residence on the continent; it is and was geographically the nearest to the land-areas of the Old World; and so far as we can trace the lines of the most ancient migrations, they diverged from that region. But there are reasons stronger than these. The American Indians cannot bear the heat of the tropics even as well as the European, not to speak of the African race. They perspire little, their skin becomes hot, and they are easily prostrated by exertion in an elevated temperature. They are peculiarly subject to diseases of hot climates, as hepatic disorders, showing none of the immunity of the African.[32] Furthermore, the finest physical specimens of the race are found in the colder regions of the temperate zones, the Pampas and Patagonian Indians in the south, the Iroquois and Algonkins in the north; whereas, in the tropics they are generally undersized, short-lived, of inferior muscular force and with slight tolerance of disease.[33] These facts, taken in connection with the geologic events I have already described, would lead us to place the “area of characterization” of the native American east of the Rocky Mountains, and between the receding wall of the continental ice sheet and the Gulf of Mexico. There it was that the primitive glacial man underwent those changes which resulted in the formation of an independent race.