192 EVOLUTION, GENETICS, AND EUGENICS 



there can be no real racial progress; and evolution is nothing more oi 

 less than racial, as opposed to individual, progress. So obvious did 

 this seem that Charles Darwin accepted as axiomatic the general facts 

 of variation and heredity and proceeded at once to a discussion 

 of the directive factors of evolution. Since variation and heredity 

 are now universally conceded to be primary factors, and selection, 

 the Lamarckian factor, isolation, orthogenesis, etc., as secondary 

 or guiding factors, it would seem more natural to proceed first to 

 a discussion of variation and heredity. So much of our present 

 knowledge of variation and heredity, however, is dependent upon the 

 background furnished by Darwin that it seems to us a more effective 

 pedagogical plan to consider first that vast and intricate conception of 

 evolution which was first given Ufe and unity by Charles Darwin, 

 and has come now to be known as "Darwinism." 



Just how broad the scope of Darwin's work and how important a 

 role he played in the development of evolutionary biology is indicated 

 in the following appreciation of Darwin which we have summarized 

 largely from the admirable statement in Professor J. Arthur Thom- 

 son's book Darwinism and Human Life. 



WHAT WE OWE TO DARWIN 



1. The web of life — the idea of linkages, interdependencies, cor- 

 relations in the living world. The idea is essentially ecological and has 

 been expressed elsewhere as "organic equilibrium." 



2. The struggle for existence — the inevitable consequence of Mal- 

 thus' idea of overproduction. This struggle is both inter- and intra- 

 specific, or may be a mere struggle against fate or against hard condi- 

 tions of inorganic environment. 



3. Variability of living creatures — an idea derived from the study of 

 changes under domestication and of diversity among wild individuals 

 belonging to the same species. 



4. Natural selection — the central idea which is to be studied pres- 

 ently. 



5. Vindication of the evolution idea. — Darwin was the first eflfec- 

 tively to marshal the evidences of evolution in sufficient force to com- 

 pel the acceptance of the fact of evolution. Much that has already 

 been presented under the head of "Evidences of Evolution" belongs 

 to Darwin. The placing of the fact of evolution on a sure foundation 

 is believed by many to have been Darwin's principal contribution to 

 science. 



