Mmi in the Light of Evolutioit 



labor by descendants. The real and full harvest 

 is reaped only at a far later time. The develop- 

 ment of the higher power or possibility involves 

 necessarily a distinct and often considerable loss 

 or renunciation of present advantage. He who 

 will save, cannot spend lavishly or freely. He 

 who will win the race must undergo training and 

 deny himself certain pleasures. This is evi- 

 dently unavoidable. It is equally clear that the 

 vertebrate was sure for a time to be overshad- 

 owed by the mollusk, and to be driven from the 

 surroundings where life was easiest. The mam- 

 mal had to be outclassed by the reptile, and the 

 arboreal form by the carnivore. It could not 

 well have been otherwise. 



Why, then, did any of our ancestors choose 

 a path which sacrificed present advantage or 

 comfort to future attainment? They did not 

 choose at all. Every one of them followed the 

 line of least resistance for him. The primitive 

 vertebrate kept swimming because those who 

 went to the bottom were eaten up by Crustacea or 

 moUusks. The swimming habit occasioned the 

 development of an internal skeleton and made 

 an external skeleton impossible until a much 

 later time. 



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