COSMIC PHILOSOPHY 



sea and ocean on the face of the globe. They 

 have raised mountains like the Andes and the 

 Himalayas at the rate of a few inches per cen- 

 tury ; they have converted extensive tropical 

 swamps into the desert of Sahara ; they have 

 repeatedly covered Europe and North America 

 with glaciers ; and they have hidden beneath 

 solid rocks vast treasures of carbon stealthily 

 purloined from the dense atmosphere of an 

 older age. 



Since such changes have ever been going on, 

 it follows that organisms have been unable to 

 remain constant and live. A race of animals or 

 plants in which no individuals ever varied would 

 sooner or later inevitably be exterminated, leav- 

 ing no progeny to fill its place. Observation 

 shows, however, that there is no such race. 

 The members of each species are ever slightly 

 varying, but, so long as the environment re- 

 mains constant, natural selection prevents the 

 variations from accumulating on either side of 

 the mean which is most advantageous to the 

 species. When the environment changes, if 

 certain variations on one side of the established 

 mean tend to bring the individuals which man- 

 ifest them into closer adaptation to the new en- 

 vironment, these individuals will survive in the 

 struggle for life, and thus the average character 

 of the species will be slightly altered. No two 

 bears have just the same amount of hair, no 

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