Wallace as Precipitant 331^ 



was to make him realize keenly the importance of the pres- 

 sure of population in eliminating the larger part of each 

 generation of living beings. 



From this point the logic in Darwin's mind was per- 

 fectly simple: More individuals are generated than can pos- 

 sibly live out their lives. No two individuals are alike, and 

 therefore some are better adapted to the living conditions 

 than others. The pressure of population will eliminate the 

 less fit. The survivors will be thus best adapted. The trans- 

 mission of their favorable variations will result in the pro- 

 gressive adaptation of their descendants to the conditions 

 of life. 



Darwin had apparently accumulated all the essential 

 facts for his purpose and needed only an illuminating flash 

 to reveal the unifying principle that was to put everything 

 in order. And this flash came from reading Malthus. 



Wallace as 'Precipitant 



Out in the East Indies the naturalist Alfred Russell 

 Wallace, exploring and meditating, was preoccupied with 

 the problem: How do living plants and animals come to 

 be what we see them to be? He was impressed with the re- 

 markable adaptation of many structures and forms to the 

 needs of life. He was impressed by the great array of species 

 intergrading so that he was plagued by the need to give 

 each distinct species a name. They refused to remain dis- 

 tinct long enough to be labeled. Meditating in the jungle, 

 he came to the conclusion that adaptation results from the 

 elimination of the less fit. He could see the conflicts and 

 struggles that destroyed the larger part of each new genera- 

 tion of eggs or seeds. He saw in the jungle the advantages 

 and disadvantages of deviation from the type. He slowly 

 worked out a theory of progressive adaptation through the 

 elimination of the unfit in the struggle for existence. 



Wallace thought he had a good idea and wrote it up in 

 a long letter to Charles Darwin in England. This was so 



