SELECTED ADAPTATIONS 447 



power at all comparable to man's influence in developing 

 artificial varieties? In the first place Darwin pointed to the 

 fact that every kind of plant or animal produces more off- 

 spring than can possibly come to maturity; for if none died 

 without issue, the progeny of one individual or pair of in- 

 dividuals would shortly cover the whole earth. Thus fifty 

 dandelion plants from one, each bearing fifty-fold, and so on 

 for nine generations, would make more than enough dande- 

 lions to occupy every foot of dry land on the globe. In- 

 numerable individuals of innumerable kinds are continually 

 producing oifspring in large numbers. Since many more are 

 produced than can mature it appears that a competitive 

 struggle for life must be going on throughout the hving world; 

 and, he argued, so intense is this struggle that if some indi- 

 viduals had an adaptational peculiarity which gave them 

 even a slight advantage over their rivals, such favored in- 

 dividuals would be the onc^s to survive and leave offspring. 

 Some of their offspring would be sure (judging from breeders' 

 experience) to inherit the same peculiarity, and these favored 

 offspring would in turn transmit it more or less enhanced 

 to certain of their descendants, and so on along lines of fa- 

 vored individuals in which the peculiarity in question would 

 become more and more pronounced. This improvement 

 would continue up to the point of adapting the organism as 

 perfectly as possible to its environment. In this way a fa- 

 vored race might become a new species through survival of 

 the individuals best fitted to a slowly changing or slightly 

 changed environment. 



The natural agencies which favor the survival of certain 

 races in the struggle for existence Darwin compared in a 

 metaphorical way to the human agencies which control the 

 production of cultivated varieties. Both Man and Nature, 

 he argued, act by selecting through successive generations 

 certain peculiarities. Man chooses to encourage what pleases 

 him. His method is Artificial Selection. Nature encourages 

 only those peculiarities which best fit the organism to its 

 environment; her way Darwin called Natural Selection. The 

 phrase has been often misunderstood through failing to take 

 it merely as a sj^mbol of the way certain natural forces act. 



