EVOLUTION SEEN IN PERSPECTIVE 3 



field had two main objectives: to convince people that evolution is indeed 

 a fact, and to present evidence in support of Darwin's theory of the means 

 and methods by which evolutionary change occurs. This theory is called 

 natural selection; it represents Darwin's special contribution to evolu- 

 tionary thought. The fundamental concepts of natural selection are pre- 

 sented in Chapter 2 and are further elaborated in Chapters 15-21. 



Ideas that by one means or another evolution does occur far antedated 

 Darwin, however. In fact, such ideas are probably as old as human 

 thought. As soon as man had attained sufficient intellect to observe the 

 similarities and differences among the animals and plants surrounding 

 him, and to speculate about them, he undoubtedly began to form crude 

 ideas of evolution. Certain it is that by the time he had learned to record 

 his thoughts so that posterity might read, concepts of evolution were pres- 

 ent in his mind. Not that these early concepts correspond in detail with 

 our modern ideas of evolution; far from it. They were highly speculative, 

 frequently colored with mythology, and represented at their best what we 

 may think of as "good guesses," since in part they were subsequently 

 proved correct. But in them we see, though dimly, the outlines of the idea 

 that the living world is one, and that living things change, giving rise to 

 new forms. 



The ancient Greek philosophers afford evidence of these early gropings 

 for explanation of the earth and its inhabitants. Space forbids mention of 

 more than a few of these pioneers in human thought. One was Anaximan- 

 der, whose adult life spanned the first half of the sixth century B.C. Ac- 

 cording to Anaximander, men were first formed as fishes; eventually they 

 cast off their fish skins and took up life on dry land. Here we have one of 

 those "good guesses." As will be evident after perusal of Chapter 8, mod- 

 ern evidence supports the view that a distant ancestor of man was indeed 

 a fish. How much credit should be accorded Anaximander for speculations 

 which proved to contain this kernel of truth? 



Xenophanes was in part a contemporary of Anaximander although, un- 

 like the latter, he lived on into the fifth century B.C. Xenophanes is cred- 

 ited with being the first person to recognize that fossils, such as petrified 

 bones embedded in rocks, represent the remains of animals that once 

 lived. Today we take the idea for granted, but that fact should not lessen 

 our appreciation of the insight shown by the first person to grasp it. Truth 

 is "obvious" only after its discovery. Xenophanes also realized that the 

 presence of fossils of marine animals on what is now dry land indicates 

 that the ocean once covered the area. 



The fifth century B.C. also saw the man who has been hailed by Osborn 



