GERMANY AND HER NEIGHBORS 241 



millions upon millions of years of evolution. Unless we assume 

 that man's evolution has been something entirely apart from that 

 of the rest of the world, we cannot for a moment expect that he 

 will be free from this intimate dependence upon the air. He may 

 mitigate the effects of conditions which depart from the optimum, 

 but he cannot alter the fact that he is part and parcel of a world 

 of life in which the condition of the air has been the determining 

 factor in the rise and extinction of type after type. 



Another step in our study of the relation between man and the 

 air around him is taken when we study history. We have seen that 

 in Rome the ups and downs of the ancient Republic and the later 

 Empire followed the vicissitudes of climate with extraordinary 

 fidelity. Here, indeed, we recognize that we are studying a prob- 

 lem so new that there is much more opportunity for a difference of 

 opinion than in the general conclusions that climatic changes have 

 been a main factor in evolution and that all forms of life are now 

 extremely sensitive to the condition of the air around them. One 

 of the most interesting phases of the historical studies of the next 

 generation is bound to be the conflict of opinion as to the effect of 

 climatic changes upon history. Yet already the evidence seems 

 strong enough at least to warrant the careful attention of seekers 

 after truth. 



In this final summary we are arranging our main points in the 

 approximate order of their probability. Many people who will 

 accept the idea that the history of Greece, Rome, and Babylonia 

 was greatly influenced by climatic conditions will scornfully reject 

 the idea that the trend of modern business is subject to any such 

 control. Their attitude is not surprising. The idea that climate 

 through its effect upon health exerts a controlling effect 

 upon mental activity, upon drunkenness, upon the ebb and flow of 

 business and upon the influx of immigrants ought not to be ac- 

 cepted lightly. On the contrary, it ought to be weighed and tested 

 from every possible angle. It cannot be held as proved until it has 

 been demonstrated in scores of different ways. Yet here, too, the 



