holmes! aboriginal AMERICAN ANTTQUITIES— PART I 41 



the sway of new conditions, and at G there would probably remain 

 but few of his activities and possibly not a single article of food 

 Imown at ^1. It is self-evident that with the progress of such a 

 movement language, social institutions, government, religion, and all 

 the arts of subsistence would be subject to frequent and decided 

 modifications, and, assuming their existence at earlier stages of 

 progress, agi-iculture, pastoral life, modes of transportation, metal- 

 lurgy, ceramics, building arts, textiles, and religious and aesthetic 

 art one by one would drop into disuse, passing little by little out of 

 the knowledge of the northward migrating people; for there would 

 be not only elimination of activities, but there would ensue quick 

 forgettings. In one environment the preceding habitat in a few 

 generations would surely be forgotten, and the knowledge of an art 

 or industry based on local products and needs lost for a generation 

 would be lost for good. 



Assuming a common place of origin for the HoTninlda' in some 

 part of the Old World, and climates and continental 



Difficulty of Reach- i i- t • j.i • x j.i j_ 



ing America rehuious Corresponding m the mam to the present, 



the probabilities seem favorable to the view that 

 dispersal to distant land areas would not take place until the 

 populations had greatly multiplied and until considerable ad- 

 vance had been made in the arts of humanity'. Under known 

 geographical and climatic conditions, America naturally would be 

 the last of the great areas to be reached. As determined by the best 

 authorities on the physical history of the Bering region, pioneer 

 immigrants, according to the period of their arrival, might have 

 been subject to at least three climatic periods: (1) A period of mild 

 climate accompanied apparently l>y changes in the land relations of 

 the continents at the close of the Tertiary era; (2) a long period of 

 remarkable climatic and other changes, known as the Ice Age, Avhicli 

 affected the northern hemisphere to an undetermined degree, and 

 which at successive periods blocked the pathway to the east and 

 possibly in some measure to the south, with intervening periods of 

 mild climate favorable to distribution, at least on the Pacific side; 

 (3) the so-called postglacial periods, which throughout have ap- 

 proximated the climatic conditions and geographical relations of 

 the present day. The duration of this period was not uniform over 

 the entire country but long or short according to the latitude, as 

 fully explained under the heading Chronology. In the northern 

 United States east of the Eocky Mountains the ice sheet persisted 

 down to comparatively recent times, estimated at from 7,000 to 

 20,000 years ago, and would have interfered with the southern move- 

 ments of population, while in the Rocky IMountain region highland 

 and the Pacific slope the glacial occupation was less complete, and 



