EVOLUTION 17 



evolution in proper perspective. As Simpson says, 'This 

 process is natural, and it is wholly mechanistic in its op- 

 eration. This natural process achieves the aspect of pur- 

 pose, without the intervention of a purposer, and it has 

 produced a vast plan without the concurrent action of 

 a planner/ 



The history of evolutionary theory abounds in attempts 

 to show that evolution contains foresight, that it moves 

 toward one or another goal in such a manner that the 

 goal seems to be predetermined. Evolution in a straight 

 line is admittedly discoverable in many instances, but 

 the majority of paleontologists agree that it does not re- 

 veal any inherently unidirectional process, much less any 

 metaphysical perfecting principle; the appearance of 

 evolution in a straight hne, where it exists, occurs be- 

 cause of the limited variability in mutation and selection 

 and because it is easier to continue a line of evolutionary 

 change, for which many of the determinants are already 

 present, than it is to start off on an entirely new Hne. 

 Moreover, if the environment is continuously changing 

 in one direction, natural selection tends to give a sus- 

 tained direction to adaptation. Hence some appearance 

 of design or purpose is inevitable in the over-all process, 

 but we cannot assign to either mutation or selection any 

 foresight, design or plan. To quote Simpson again, "There 

 is neither need nor excuse for postulation of nonmaterial 

 intervention in the origin of life, the rise of man, or any 

 other part of the long history of the material cosmos.' 



We can speak of 'progress' in evolution, but progress 

 is not the essence of it. Aside from the continued filling 

 of the world with highly diverse forms of Hfe (a process 

 which also has had its ups and downs) there is no sense 

 in which it can be said that evolution is intrinsically 

 progressive. It is only 'opportunistic,' in that every con- 

 ceivable device gets tried and the problem is frequently 

 solved in more than one way. It has been pointed out 

 that the variety of photosensitive cells that have been 



