146 SOCIAL EVOLUTION 



desert. The complex bows of the Eskimo appear to be 

 due to the lack of any long elastic material for bow- 

 staves, and various devices have been invented for secur- 

 ing elasticity of the bow where elastic wood is diflinilt 

 to obtain. Tribes without permanent habitation resort 

 to skin receptacles and baskets as substitutes for pot- 

 tery." 



During the thousands of years before history was 

 \\rittni primitive men were subjected to the varying 

 climatic influences which we have described. These cli- 

 matic influences were conditions to which primitive men 

 had to adjust and adapt themselves as best they might. 

 A great climatic change which caused the desiccation of 

 a large and highly populated area killed off its human 

 inhabitants by thousands. Those whose constitutions 

 were plastic enough to withstand the change and make 

 the necessary adaptations survived; others perished or 

 migrated to more favorable territory. In the course of 

 migrations, these early peoples not possessing our knowl- 

 edge of means of transportation and communication, 

 were subordinated to the natural barriers or means of 

 travel such as mountain masses and valleys. The sur- 

 face of the earth has determined the movements of popu- 

 lations and the migrations of races from those areas 

 wliich climatic changes have made uninhabitable. 



Valleys offer channels for the easy movement of hu- 

 manity. They are grooves which have time and again 

 determined the destination of aimless, unplanned mi- 

 grations. The passing of peoples follows these nature- 

 made highways. "The maritime plain of Palestine has 

 been an established route of commerce and war from Un- 

 tune of Sennacherib to Napoleon. M Up the Danube valley 



"Boas, op. cit., p. 100. 



