518 THE CHANGING WORLD 



The Natural Selection Theory of Darwin 



The Theory of Natural Selection was arrived at independently 

 and simultaneously by Charles Darwin (1809-1873) and Alfred 

 Russell Wallace (1822-1913). It is greatly to the honor of these 

 two gentlemen that neither one jealously claimed priority for the 

 idea. They remained throughout life friends rather than rivals. 

 Darwin's elaboration was the more exhaustive of the two, and 

 consequently his name is more often the one associated with the 

 theory. 



When a young man, Darwin, as naturalist on board the Beagle, 

 which was employed by the British Government in making extensive 

 surveys for navigation, spent five years ''seeing the world." For the 

 next twenty years he mulled over what he had seen, adding to it 

 by exhaustive study and experiment, before he was ready to publish 

 his results. The Origin of Species appeared in November, 1859, and 

 the entire first edition was sold out on the first day. There is no doubt 

 that it is the most famous scientific book of the nineteenth century. 

 It has gone through many subsequent editions and has been trans- 

 lated into many languages. It is the parent of whole libraries of 

 intellectual children. The thoroughness with which the work was 

 done, and the restraint and caution employed, explains why the 

 edifice of Natural Selection there set forth has withstood the battering 

 storms of controversy during subsequent years. That part of the 

 theory which has been modified necessarily to make it square today 

 with the advance of biological knowledge has to do largely with the 

 nature of variations and the mechanism of heredity. The central 

 thesis stands. 



Darwin was impressed with the effectiveness of human selection 

 in the formation of domestic species, and extended this idea to include 

 nature as the selective agent instead of man. The essentials of 

 Darwin's theory are as follows : (a) variation occurs in all organisms ; 

 (6) universal prodigality of reproduction tends to overpopulation; 

 (c) a struggle for existence results, which tends to check overpopula- 

 tion ; (d) survival of the best adapted to survive, and the elimination 

 of the unsuccessful, follows the struggle for existence ; (e) the life- 

 saving qualities so selected by nature are transmitted to the offspring 

 and become the cumulative heritage of the race ; (/) hereditary 

 characteristics acquired through natural selection are prevented by 

 isolation, either geographical or physiological, from cancellation or 



