452 SECTION H. 



4. Favorable for agriculture and production of economic 

 surplus. 



The sub-environments more favoring in the struggle for ex- 

 istence are : 



1. Mountains at sources of rivers. Here are narrow valleys 

 for agriculture with occasional irrigation; game, nuts, fruits 

 and plants; timber; building material, etc. The temperature 

 cold with short growing season. 



2. High plateaus with marshes, lakes, ponds. Tand lying 

 well for catchment of water. Temperature as in 1 . 



3. Mesa country, with broad plains and valleys; springs; 

 streams flushed at seasons. 



4. Riverain lands in lower stream valleys suitable for 

 irrigation by canals or warping. 



The effect of this environment upon plants is to reduce 

 them to their lowest terms ; animals, to modif y them in import - 

 tant ways ; man, to subject his mind to the stress of severe con- 

 ditions, reacting noticeably on his body, and mightily on his 

 thought and material progress. 



The environment was suitable; or extinction of tribes followed 

 or a movement was made to a new sub -environment. Thus 

 the constant and seemingly erratic migration of tribes which 

 have covered the Pueblo region with remains of ancient towns 

 may have been due to natural causes which disenvironed them, 

 such as earthquakes, failure of springs, etc. The final localiza- 

 tion of the pueblos is an index, in large measure, of the 

 reginal fitness. 



It is probable that the tribes coming into the Pueblo en- 

 vironment were at first confined to mountain regions where 

 there is a permanent water supply and natural subsistence, 

 and that gradually they spread along the water courses and into 

 all the sub -environments. With the increase of population 

 the building of permanent villages of stone, the beginning or 

 extension of the agriculture of maize — which cereal is a major 

 factor in the distribution and permanency of tribes — the settle- 

 ment of the Pueblo region went on apace. 



