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 difficult 

 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 

 written primitive men w-ere 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 tliemselves 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 wdiose 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 eartli has determined the movements of popu- 

 lations and the migrations of races from those areas 

 which climatic changes have made uninhabitable, 

 -^alley-s- 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 the 

 time of Sennacherib to Napoleon. ' ' Up the Danube valley 



32 Boas, op. cit., p. IGO. 



