CLIMATE IN SOME OF ITS RELATIONS TO MAN 261 



agricultural lands. Wheat and corn are replacing grass on the steppes, 

 especially where irrigation can be practised. Deserts are being re- 

 claimed here and there where water is available. The more civilized 

 man becomes, the denser the population which the different parts of 

 the earth can be made to support. From the wandering hunting and 

 fishing tribes of the African forest or of the borders of the Arctic Sea, 

 through the farming populations of the cleared forest and of the 

 steppe, to the crowded industrial centers of the modern city, there is 

 such a gradation. It is the story of a more complete to a less complete 

 mastery of man by his environment. 



But in spite of all that man can do, the larger climatic limitations 

 persist. The Greenland desert of snow and ice, the Saharan desert of 

 sand : these remain, deserts. 



Primitive Civilization and the Tropics. — There are reasons for think- 

 ing that primitive, prehistoric man, in his earliest stages, when most 

 helpless, was an inhabitant of the tropics ; that he lived under the mild, 

 uniform, genial climate of that zone, where food was easily obtained 

 and protection against the inclemencies of the weather least necessary. 

 There has been a belief that southern Asia, with its numerous bays and 

 archipelagoes, was probably the cradle of humanity. Civilized man is 

 believed by many to have appeared first on the delta formed at the 

 head of the Persian Gulf by the Tigris and Euphrates rivers. Ancient 

 civilizations seem to have developed in the drier portions of the tropics, 

 where irrigation was necessary in order to insure abundant and regu- 

 lar crops, and where lived races more energetic and more hardy than 

 those of the damper and rainier portions of the tropics, with more 

 luxuriant vegetation. Within the tropics, the greatest progress later 

 came, not on the damp lowlands, but on the less fertile plateaus of 

 Mexico and Peru, where the Aztecs and the Incas made their marvelous 

 progress in the drier, cooler and somewhat more rigorous climates over 

 7,000 or 8,000 feet above sea-level. 



The Development of the Tropics. — Within the tropics, under the 

 equatorial sun, and where there is abundant moisture, animal and 

 plant life reach a very full development. Here are the lands which 

 are most valuable to the white man because of the wealth of their 

 tropical products. Here are the tropical " spheres of influence " or 

 " colonies " which are among his most coveted possessions. It is in 

 this belt that food is provided for man throughout the year without 

 labor on his part; where shelter and clothing are so easily provided, 

 and often so unnecessary, that life becomes too easy. Nature does too 

 much; there is little left for man to do. The simplicity of life, so far 

 as providing food is concerned, has been emphasized by writers almost 

 without number. Captain Cook put the case very emphatically when 

 he said that a South Sea Islander who plants ten bread-fruit trees does 



