de Beer • The Darwin-Wallace Centenary 



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kewemis. Many other new species have 

 originated by intentional h)bridization 

 and accidental polyploidy in this way. 

 Some of these artificially produced 

 species have been found to be identical 

 with, and to breed with, wild species, 

 and this is the proof that this method 

 of species formation occurs in nature. 



THE CENTENARY OF EVOLUTION 

 BY NATURAL SELECTION 



In conclusion, it may be said that 

 during the hundred years that have 

 elapsed since Darwin and Wallace first 

 published their theor)', the fact of or- 

 ganic evolution is now universally ac- 

 cepted and its mechanism has been 

 formally explained. 



The alternative to evolution is so 

 naive that it comes as a shock to realize 

 that as recently as one hundred years 

 ago, ideas such as called for the follow- 

 ing questions could still be current: 

 "Do they really believe that at in- 

 numerable periods in the earth's history 

 certain elemental atoms have been 

 commanded suddenly to flash into liv- 

 ing tissues? Do they believe that at 

 each supposed act of creation one indi- 



vidual or many were produced? Were 

 all the infinitely numerous kinds of 

 animals and plants created as eggs or 

 seeds, or as full grown? And in the case 

 of mammals, were they created bearing 

 the false marks of nourishment from 

 the mother's womb?" Darwin might 

 well allow himself to ask these ques- 

 tions, for he and Wallace had found 

 the answer to them. 



So soundly was the theor}' of evolu- 

 tion by natural selection grounded that 

 research does nothing but confirm the 

 links in its chain of evidence and the 

 inferences to be drawn from them. Its 

 field has extended from the explana- 

 tion of the production of plants and 

 animals to every aspect of the intellec- 

 tual life of man, and it would be im- 

 prudent to doubt that its greatest tri- 

 umph may yet lie in the highest aspect 

 of that life. Only a genius could have 

 discovered a key of such simplicity to 

 so great a problem. Only ignorance, 

 neglect of truth, or prejudice could 

 actuate those who, in the present state 

 of knowledge, without discovering new 

 facts in the laboratory or in the field, 

 seek to impugn the scientific evidence 

 for evolution. 



QUESTIONS 



1. What three main observations did Dar- 

 win make on his voyage which stimu- 

 lated his thinking about the immuta- 

 bility of species? 



2. What are the evidences of evolution 

 from: a. domestic plants and animals, 

 b. comparative anatomy, c. embry- 

 ology, d. paleontology? 



3. Briefly discuss the relationship of Dar- 

 win's ideas on evolution to those of 

 Wallace. 



4. Outline Darwin's Theory of Natural 

 Selection. 



5. What part does "blending" inheri- 

 tance play in modern evolutionary 

 theory? Explain. 



6. What are some of the objections to 

 natural selection? 



7. Discuss the moth in England as a 

 proof of evolution. Does this prove 

 evolution, the immutability of species, 

 or both? 



