42 BUREAU OF AMERICAN ETHNOLOGY [bull. 60 



it is possible that passage from north to south was never wholly 

 interrupted. 



In the absence of definite knowledge of the period of arrival of 

 the pioneers and the beginning of the American occupancy, and of 

 the climatic and other conditions to which all preglacial and glacial 

 movements w^onld be subject, it seems vain to enter upon a pro- 

 longed theoretical discussion of the possible processes and progress 

 of settlement during these periods. If, however, man by whatsoever 

 routes he may have taken eventually did reach the gateway during 

 these periods, there is no known reason why, at least during the 

 intervals of milder climate, he should not have entered America and 

 passed southward, if not eastward, over the northern continent. 



Tribes acclimated in Siberia would readily make a home in the 

 valley of the Yukon, but considerable time might elapse before they 

 would overcome the intervening difficulties and reach the valley of 

 the Columbia, the Mississippi, or the St. Lawrence. The journey 

 along the coast from the Aleutian Peninsula to Sitka is practically 

 impossible for any except peoples having seagoing craft. The cross- 

 ing from the headwaters of the Yukon into the forest-covered area 

 of the Northwest Coast or into the MacKenzie Basin would meet, 

 aside from the possible interference of glacial ice, wdth untold diffi- 

 culties for primitive peoples. 



It may be assumed that movements southward would be, at first, 



extremely tedious and confined to very meager bands 



Movements at ^' ^yaj^^igj-ers, but the progress could well be more 



First Tedious ' . 



rapid than the spread of tropical Asiatic peoples to 

 the north, as described in the preceding section. Instead of advanc- 

 ing against new and unfavorable conditions of climate, the progress 

 in America would be constantly to milder climates and more plentiful 

 food supply. Then, again, successive advances in culture necessarily 

 occurring would give distinct advantage to wanderers in the new 

 land. The spread over the Mississippi Valley to the Gulf would be 

 quickly accomplished, and from the central area the east and the west 

 would be occupied with comparative ease. 



The passage of peoples from North into South America would 

 present no insurmountable difficulties under geographical conditions 

 corresponding to the present. Unoccupied, these areas would offer 

 no resistance to the advance of the pioneers, although the Isthmus 

 might hinder on account of its prevalent jungles, marshes, and 

 febrific dangers. 



The passage from either North or South America to the Caril)bean 

 Archipelago would probably present problems closely akin to those 

 of the passage of Bering Strait in the present period. 



