THE EVOLUTIONARY CONCEPT 331 



putting together the results of a great many different lines of research. 

 These include the study of fossil records of past life and their sequence 

 in time ; detailed comparisons of the structure and function of organisms 

 in the search for fundamental similarities; analysis of the variation 

 within species including its causes and mode of inheritance; and studies 

 of populations with regard to environmental influences exerted by such 

 factors as selection and isolation. All branches of biology and many of 

 the other sciences have contributed important data. And from all this 

 work, carried out by scientists of many countries over a long period of 

 time, one great unifying concept has emerged — the principle of organic 

 evolution. It will be worth while to review the steps by which this principle 

 became established. 



THE DEVELOPMENT OF THE DOCTRINE OF ORGANIC EVOLUTION 



Practically all scientists and most educated persons now accept organic 

 evolution as an established principle. It has not long held this status, 

 however, and even today many people who lack biological background 

 and the objective viewpoint of science refuse to admit its truth. The rea- 

 son why this attitude toward evolution survives, while other scientific 

 generalizations of similar scope are unquestioningly accepted, lies in the 

 conscious or unconscious assumption that man is something wholly 

 apart from the rest of the living world — that he differs qualitatively from 

 other organisms and is, so to speak, the center and apex of creation. To 

 people who feel thus, anything that shows man to be related to the rest 

 of the animal kingdom, however remotely, is disturbing and objectionable, 

 or even sacrilegious, if one takes the Mosaic account of creation literally. 



In relation to organic evolution the objectivity of science has often come 

 squarely into conflict with popular belief and emotion, producing bitter 

 controversies that are now fortunately almost a thing of the past. The 

 historic background of the unnecessary conflict between science and 

 religion will be traced in brief outline, together with the nature of the 

 evidence that forced men of science to accept the reality of evolution. 

 Here we shall once again see the scientific method at work — the accumula- 

 tion of observations that cried out for explanation, the somewhat groping 

 formulation of hypotheses to account for them, the testing and revision 

 of these hypotheses, and the eventual discarding of all but one, which 

 became established in modified form as an accepted principle. 



Early evolutionary speculation. From the earliest times men have 

 sought a satisfying explanation of the universe and of their own place 

 and significance in the scheme of things. Prior to the development of 

 science it was natural that their explanations generally took the form 

 of nature myths, in which plants, animals, and men were created by 

 some supernatural agency. Such creation myths have arisen among 



