ORIGIN OF THE LIVING MACHINE: ADAPTATION 353 



Darwin, the method by which new forms were produced was 

 by the law of natural selection. Very briefly stated, that law 

 is as follows : 



1. Overproduction. All animals and plants tend to multiply 

 more rapidly than it is possible for them to continue to exist. 

 More offspring are produced by even the slowest breeding ani- 

 mals and plants than can possibly find sustenance in the world. 



2. Struggle for existence. As the result of overproduction, 

 the individuals that are born are engaged in a constant struggle 

 with each other for the opportunity to live. This struggle is 

 sometimes an active and sometimes a passive one; and sometimes 

 it is a struggle with each other for food. It is a struggle in which 

 only the victors remain alive, the vanquished being exterminated 

 without living long enough to leave offspring. 



3. Variation, or diversity. All animals and plants show a 

 large amount of diversity among themselves, and, as a result, 

 some must be better fitted for the struggle for life than others. 



4. Natural selection, or the survival of the fittest. It is a logical 

 result of the struggle for existence that only those individuals 

 best fitted for the struggle will be the ones, in the long run, to 

 win in the contest. Hence the "fittest" in the long run will 

 survive, while those less fitted to exist will be exterminated 

 in the merciless struggle for existence. 



5. Heredity. By the law of heredity, individuals transmit 

 to their offspring their own characters. Hence if one individual 

 survives the struggle for existence by virtue of some special 

 characteristic, it will transmit this characteristic to its offspring. 

 The offspring will inherit it, and in the course of a few genera- 

 tions the only individuals left alive will be those that have 

 developed the favorable characteristic in question, while those 

 that did not develop it will be exterminated by the law of 

 natural selection. 



As the result of these five factors working together, Darwin 

 supposed that there would be a constant accumulation of favor- 

 able characters, each generation being to a slight extent an 



