THE EVOLUTION OF MAN 



advantage, but certain individuals which departed 

 most widely from the parent form in a certain 

 direction corresponding most nearly to the new 

 requirements. Take it, for instance, that the 

 climate changed. A plain formerly covered with 

 a brownish mould was suddenly and permanently 

 covered with snow. The brown plain had been 

 inhabited by brown rabbits. Up to the time of 

 this sudden change it was always those individ- 

 uals of the offspring which most closely re- 

 sembled in color the tint of this plain that sur- 

 vived in the struggle for existence; for brown 

 coincided with brown and was not easily detected 

 by the enemies of the rabbits. But now white 

 suddenly became the best adapted color. Hence- 

 forth those rabbits had the greatest chance to 

 survive which happened to be white as a result 

 of individual variation. These were now pre- 

 served, they propagated their kind and left be- 

 hind them a growing number of young, which 

 continued to marry white with white. In the 

 course of years the entire rabbit nation became 

 white an adaptation to snow. 



This logic of Darwin's seems irresistible so 

 long as we admit that individual variations al- 

 ways offer sufficient material for selection in 

 other words, that there were always a sufficient 



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