December. 1927 



EVOLUTION 



What Is Evolution ? 



By Henshaw Ward 



TT is astonishing to see how often "evolution" is miscon- 

 ceived by educated people, sometimes even by scien- 

 tists. Learned journalists and professors have upheld 

 or derided evolution without first inquiring what the 

 theory really is. I will briefly describe how it originated, 

 how inescapable it is, how simple and restricted it is. 



Since the time of Aristotle there has been in the 

 world a theory that in some unknown way, animals and 

 plants have developed from previous simpler forms. 

 This idea arose very naturally from the mere observation 

 of the way in which the 

 kinds of animals form a sort 

 of series from lowly plant- 

 like forms to quadrupeds. 

 From the lowest plants to 

 man there is no big gap in 

 the scale of forms: all ani- 

 mate nature appears to be a 

 sort of gradation. No won- 

 der that Aristotle and Lu- 

 cretius and Leonardo da 

 Vinci guessed that the great 

 array of living beings might 

 have diverged from some 

 primitive creatures. 



But this was merely spec- 

 ulation. Not until the eigh- 

 teenth century was there any 

 real effort by naturalists to 

 explain how such transmu- 

 tation was possible. The 

 most original and powerful 

 of the early reasoners was 

 Buffon, who set forth an in- 

 genious conjecture in 1750 

 — that changes of climate 

 and food cause alterations 

 in animals, and that these al- 

 terations are inherited, con- 

 tinuallv diverging more 

 widely from the parent stock. Henshaw 



Buffon argued persuasively from the changes known to 

 be brought about in a series of generations by domesti- 

 cation. Forty years later Erasmus Darwin, grandfather 

 of Charles Darwin, took up Buffon's idea, modified it 

 by his own wide and keen observation, and argued for 

 its probability. In 1809 the great French naturalist, 

 Lamarck, reasoned that the principal cause of the trans- 

 formation of species was the changes brought about in 

 animals by their strong and repeated efforts to satisfy 

 their desires. In 1844 a Scotchman, Chambers — though 

 he called Lamarck's reasoning foolish — upheld La- 

 marck's conclusion in an ingenious little book called 

 Vestiges of Creation. 



These four imaginative men — no others were import- 

 ant in comparison — kept alive a development theory and 

 had a few followers, but the total effect of their reasoning 

 on scientific thought was almost nil. Huxley has vividly 

 described how disreputable the theory was in the fifties, 

 and Weismann testifies that he could not even learn 

 about it in respectable books during his student days of 

 that period. 



Darwin, after five years of zealous observation in a 

 voyage round the world, set himself to study the species 

 question in 1837. For twenty years he amassed evidence, 

 letting only two friends know what he was about, and 

 receiving little encouragement even from them. His 

 Origin of Species in 1859 set forth, as Huxley unequivo- 

 cally states, an idea "that was wholly unknown to scien- 

 tific thought before 1858." 



All previous thought had assumed that environment 

 somehow produces changes in animals. Darwin saw that 

 the truth was the other way 

 round — that changes origi- 

 nate in the embryo of every 

 plant and animal, by a proc- 

 ess quite unknown to us; 

 that these spontaneous varia- 

 tions can be inherited; that 

 if they are harmful they will 

 not survive in heredity; that 

 if they are advantageous 

 they will be perpetuated, 

 will tend to increase, and 

 will finally cause a race to 

 differ so much from its an- 

 cestors that it will be called 

 a new species. 



Darwin, by a sort of 

 parable, likened the forces 

 of nature to a breeder, who 

 selects variations. He said 

 that nature acts as if it 

 "selected" unfavorable var- 

 iations and discarded them, 

 while keeping the favor- 

 able ones to form new 

 races. 



This idea was a mere hy- 

 pothesis when Darwin pub- 

 lished it. He did not claim 

 that he had proved any- 

 thing; he simply showed 

 ;e the strong probability that 

 ed what facts could be found 

 what other theory could be 



Ward 



from his wealth of knowled 

 his idea was true, and he asl 

 hat were opposed to it or 



suggested that would fit the great variety of known facts. 

 Darwin's theory was not accepted because it was clever 

 reasoning about one department of science, but because 

 it neatly fitted all the widely separated departments. It 

 explained the geologic record, the mazes of clas,sification, 

 the life of an embryo, the puzzles of distribution, the 

 marvels of adaptation. It has ever since become increas- 

 ingly obvious that a theory which accounts for all these 

 unrelated fields and bring them into a scientific harmony 

 must be true — unless the universe is a whirlpool of 

 unreason. 



Some modern students of heredity minimize Darwin's 

 "natural selection" and feel that they are going to dis- 

 cover a rather different way of explaining evolution. 

 They are so much concerned, in their special work, with 

 the mode of evolution that they give the public the 

 impression they are attacking an evolution theory. 

 For one example: Bateson spoke out so radically in 



