PRESENT PROBLEMS 223 



nations, each having a period of prosperity followed by a period of 

 decay and a final disappearance. That nations have a period of 

 youth, manhood, and decay that the history of each individual 

 life is repeated in the history of nations is a view based on the 

 economic conditions of Southern Europe and Western Asia. 



But is this law of the rise and decay of nations a general law 

 or a peculiarity of the region where southern civilization arose? 

 It is plainly a local law. I have only to show that the slight rain- 

 fall of these regions has geologic causes in order to demonstrate that 

 the decline of nations was due neither to social conditions nor failings, 

 but was the inevitable result of changed climatic conditions. 



Progress is due to the increase of resources; decline in civilization 

 follows a failure of resources. A tragic end awaits a nation cramped 

 by a reduction of the food supply. There are many ways of proving 

 this, but I shall take a bold one that demands some imagination. 

 The land masses of this central basin seem in early historic epochs 

 or in those that immediately precede them to have risen to higher 

 levels, converting many depressions occupied by lakes and seas into 

 sandy wastes. Lower the level of the Sahara by five hundred feet 

 and it would become an inland sea. When this region was covered 

 with water the southwest winds were moist and carried abundant 

 rains to the eastern plateaus. Arabia and Persia could then have 

 lakes where now there is only blowing sand. The high lands would 

 have a verdant foliage and be fit centres for growing nations. 



When civilized men gained a foothold in this region the elevation 

 of land may have been completed and the decline in rainfall begun. 

 The uplands would so become fine grazing land and the lowlands 

 would be centres of agricultural activity. Careless tillage and the 

 destruction of trees would increase the natural denudation of the 

 uplands and render them less habitable. This would force an unrest 

 in the upland population, a movement to lower levels and a struggle 

 for their possession. This contest, once begun, would be a perpetual 

 process. Each downward movement of population would develop 

 a new civilization, enduring until another unrest in the highlands 

 brought a new horde of barbarians to destroy it and in turn to 

 develop a new one. Region after region was thus denuded and 

 civilization after civilization fell before the steady pressure of the 

 upland races forced out of their habitat by the increasing dryness. 

 A decreasing rainfall and an increasing denudation of land forces 

 nations to move rapidly through the various stages of progress 

 and in the end crushes them through the lack of resources. 



There is, therefore, a long series of these short-lived nations, 

 each repeating the other's history, because back of them were the 

 same processes of growth and decay. The tradition of these se- 

 quences is the basis of the maxim that history repeats itself, while 



