2 EVOLUTION 



We will, however, not linger in examining definitions 

 of evolution, but will be content to give some shape to 

 the vague idea which everybody now attaches to the 

 word. Evolution does not mean merely a long life of 

 change. Here, for instance, is a tiny worm-like creature 

 that lives parasitically inside another animal. Its an- 

 cestors have done so for ages, and the form has been 

 greatly changed during those ages. Yet, instead of 

 evolving, it has done the very opposite. It is an example 

 of what is called " devolution," or evolution turned back- 

 wards. If you could imagine a modern locomotive 

 getting amongst a backward people, who fell short of the 

 model each time they made fresh ones, and at last pro- 

 duced something like Stephenson's primitive " Rocket," 

 you would have some idea of change through many 

 generations without evolution. Evolution means ad- 

 vance from simplicity to orderly complexity, from a loose 

 association of a few parts to an elaborate and definite 

 association of many parts, from vague general characters 

 to a number of very definite and particular characters. 

 The original dog was not like any living dog, but had 

 only those features which the present different kinds of 

 dogs have in common. Earlier still was an animal with 

 the features that are now common to the dog, wolf, and 

 fox; still earlier one with the general features of the cat> 

 tiger, and lion as well. 



This idea of advance from vague general objects to 

 very definite, complex, and specialised objects is the idea 

 of evolution that we apply to the universe and all it 

 contains. All the plants are specialised descendants of 

 a tiny simple speck of living matter that floated in the 

 primitive ocean tens of millions of years ago. All the 

 countless species of animals descend from a jelly-like 

 speck that was not far removed from the first plant. 

 All the bodies in our solar system are condensed pieces 



