OLD CROW 153 



1947) diminished in thickness north of about latitude 54° and probably 

 did not reach the Porcupine Valley. Massive though probably not 

 continuous glaciers occupied valleys of the Brooks Range, but much 

 of the Yukon Porcupine Valley system was free from continuous ice, 

 as was also the arctic slope of Alaska. Thus northern Alaska and 

 Yukon, while not covered with ice were cut off from habitable America 

 by ice which apparently reached the sea west of the mouth of the 

 Mackenzie and along the Pacific shores of Alaska. 



We can speculate that hardy birds like those now resident in the 

 Arctic might have survived the last glacial maximum in arctic Yukon. 

 There is no doubt that the invasion of migratory birds has occurred 

 since their paths from the south have become free from ice. The 

 10,000 years smce the last maximum of glaciation have had fluctua- 

 tions in climate and in the attendant condition of the land surfaces. 

 If migrations have been long in operation the birds must have had a 

 remarkably varying experience in their migratory routes. Not only 

 have the climatic conditions changed but the changes in populations 

 accompanying the opening and closing of great areas must have 

 exerted powerful and changing social influences. Through this period 

 of change, however, the essential features of the Rocky Mountains 

 and Brooks Range have continuously maintained a northern Yukon 

 and Alaska geographically and climatically distinct from the adjacent 

 regions. At present we have then the maximal duration of time of 

 development of modern migrations, which passed through areas of 

 great climatic and biotic change and which are now established in a 

 geographically distinguishable area. 



Modern Indians seldom pass into the barren coastal mountains of 

 Yukon Territory, the traditional barrier and boundary between them 

 and the Eskimo people with whom they have long had hostile, or at 

 best unfriendly, relations. There has probably been some exchange of 

 material culture but the distinction between Indian and Eskimo 

 ways is striking for neighboring people in similar climates. Among 

 names of birds, for example, Indian and Eskimo names for about 90 

 species known by both people show resemblance in only three cases 

 (Irving, 1958b), and I think that this instance about represents 

 their general resemblance in respect to intellectual culture. Even in 

 material culture it is surprising to see that their few natural resources 

 have been used in many cases with such differing implement and fash- 

 ions, and judging from what I have heard from them the blood of 

 the two races has seldom mixed (Lewis, Chown, and Hildes in 1959 

 reported that blood samples taken in 1958 from most of the Indian 

 population of Old Crow showed no serological evidence for inter- 

 mixture with Eskimos) . 



