CHAPTER XVI 



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EVOLUTION 



From specific statements made here and there in the foregoing 

 chapters, and from inferences inevitably drawn from various facts therein 

 related, the student can hardly have escaped drawing the conclusion 

 that the animals of today are not like the animals that once inhabited the 

 earth. Such a conclusion will have been strengthened by much that is 

 discovered at first hand in the laboratory. To explain many of the facts 

 of structure and development in Hving organisms, the nature of fossils, 

 and the distribution of living animals and plants, it seems necessary to 

 assume that species have undergone gradual changes. This gradual 

 change is called evolution, and species are said to have evolved. Man has 

 baen one of the products of evolution no less than other animals. Not 

 one species of living organism has escaped the modifications that con- 

 stitute evolution. Though some lands of organisms have been relatively 

 constant, while others have been altered rapidly and often, there is no 

 species alive now which is not different from its most remote ancestors. 

 Close similarity between modern and ancient hfe is limited to low forms. 

 Nor has evolution been confined to the past; it is going on today. Not 

 every species is evolving now, so far as can be discovered, but some species 

 are. A few years or a few centuries hence, the species now undergoing 

 modification may have reached a fairly stable condition, and other species, 

 now apparently constant, be in a period of alteration. 



Darwin and the Rise of the Evolution Theory.— A brief historical 

 account of ideas of evolution has been given in the first chapter. As 

 was pointed out there crude ideas of evolution were held by individuals 

 even as early as the Greeks. Noteworthy theories were proposed by 

 Lamarck and others at the end of the eighteenth century and in the early 

 nineteenth century. Wide acceptance of the doctrine of evolution, how- 

 ever, dates only from the time of Charles Darwin (Fig. 233) who has the 

 distinction of having brought together so many facts indicating evolu- 

 tion, together with a theory to account for the facts which was so plau- 

 sible, that thinking people were everywhere driven to adopt his views. 

 The life of Darwin and the history of the evolution idea as developed by 

 him stand, therefore, in much the same relation to the evolutionist as do 

 the great epic poems to the student of literature or the story of the Magna 

 Charta to the historian of constitutional government. A brief account 

 of the origin of modern ideas of evolution may well be added to the 

 general statement made in Chapter L 



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