CHAPTER IX 



EVOLUTION 



HISTORY OF EVOLUTION THEORY 



VAGUE GREEK EVOLUTIONISM.— The general idea of Organic 

 Evolution is that living creatures have come to be as they are from 

 relatively simple beginnings by a gradual process of racial change. 

 This idea is congruent on the one hand with individual development 

 and on the other hand with human history; and therefore one expects 

 to find it expressed in ancient times. And so it is, for a vague evolu- 

 tionism is stated by many of the old thinkers, such as the Greek 

 Philosophers. Thus Empedocles seems to have thought of the 

 Becoming of Life as gradual, of plants appearing before animals, 

 of the imperfect being gradually replaced by the perfect, and, most 

 remarkable of all, of the extinction of the imperfect being a condition 

 of the rise of the perfect. The last idea approaches the theory of 

 Natural Selection. It must be admitted, however, that most of the 

 ancient philosophers were very abstract in their evolutionism. 

 When they condescended to the concrete, they seem to have pic- 

 tured a gradual Becoming of a mysterious nature, — successive 

 births from the earth's fertile womb. They had not the modern idea 

 of one species giving rise to variations which form new species, the 

 old and the new often living on together. Fine expositions of the old 

 Greek evolutionism will be found in H. F. Osborn's From the Greeks 

 to Darwin, and Zeller's Griechishe Vorgdnger Darwin's. It should be 

 noted that according to some authors, such as Edward Clodd in his 

 Pioneers of Evolution, the Greek philosophers were nearer modern 

 evolutionism than they usually get credit for. But analogy in thought 

 is sometimes mistaken for homology. 



ARISTOTLE. — As Aristotle had an intimate knowledge of many 

 animals, and probed into such apparent minutiae as the eye of the 

 mole and the early development of the chick, he may well have 

 thought of Organic Evolution, and much more concretely than his 

 predecessors. As a matter of fact he was very reticent on the 

 subject, though he seems to have pictured an age-long genetic 

 advance. "Nature can only rise by degrees from lower to higher 

 types." "Things, being continually moved by a certain principle in 

 themselves, arrive at a certain end." This is an early expression of 

 the often recurrent idea of an inherent perfecting principle, which 

 is not very far from one of the modern theories — that of "orthogenic 

 variation", i.e. of progressive change along a definite line. It is 



