4 INTRODUCTION TO EVOLUTION 



(1896) as "the father of the Evolution idea": Empedocles. According to 

 this philosopher, plants arose out of the earth, as did, subsequently, ani- 

 mals. Animals arose as unattached organs and parts which joined together 

 in haphazard fashion. Most of these conglomerations were freaks and 

 monsters incapable of living, but occasionally a combination of organs ap- 

 peared which could function as a successful living organism. Such success- 

 ful combinations survived and populated the earth, while the incongruous 

 assemblages died. It is possible to see in this account the first glimmerings 

 of the idea of the survival of the fittest, an idea which formed such an im- 

 portant part of Darwin's theory of natural selection twenty-three centuries 

 later. But the danger is great of "reading into" such ancient writings ideas 

 which were not actually in the mind of the author. Empedocles included 

 man among the beings formed in the manner described. 



The fourth century B.C. is memorable for the life and work of Aristotle, 

 well termed by Locy (1925) "the greatest investigator of antiquity." 

 Best known to us as philosopher, Aristotle possessed far more of the spirit 

 of scientific research than did his predecessors, or than did most of his 

 successors for centuries to come. Thus, within the limits of the materials 

 and methods available to him he carried on investigations in such diverse 

 fields as marine biology, anatomy, embryology, and the metamorphosis of 

 insects. Although the accuracy of his scientific observation excites our ad- 

 miration, we find less to admire in his speculations concerning evolution. 

 There he failed to follow the ideal which he himself propounded: "We 

 must not accept a general principle from logic only, but must prove its ap- 

 plication to each fact; for it is in facts that we must seek principles, and 

 these must always accord with facts." Yet our censure must be temperate, 

 since the store of "facts" available to Aristotle was totally inadequate as 

 foundation for the activity of his towering intellect. 



We shall confine our attention to one contribution made by Aristotle 

 to evolutionary thinking. He maintained that there is complete gradation 

 in nature. The lowest stage is the inorganic. Organic beings arose from 

 inorganic by direct metamorphosis. He conceived the organic world to con- 

 sist of three states: (1) plants; (2) plant-animals, a transitional group in 

 which he included sponges and sea anemones; (3) animals, characterized 

 by feeling or sensibility. Within the animal group he constructed a genetic 

 series leading from lowest forms up to man, placed at the apex. Hence, we 

 may think of Aristotle as the father of those "family trees" which have 

 been so conspicuous in writings on evolution ever since. It is to be noted, 

 however, that his tree had no branches; it was a straight line from polyps 



