THE DYNAMICS OF EVOLUTIONARY CHANGE 



by a variety of prehuman types, many of which are represented 

 by a considerable number of individual fossils. As Le Gros 

 Clark (1959) has emphasized, these new finds have definitely 

 filled in some of the gaps. They have made it highly probable 

 that the fossil primates which are waiting to be unearthed will 

 eventually give us a continuous sequence extending from the 

 ape- or monkey-like common ancestor which existed thirty or 

 forty million years ago up to modern man. 



SOME THOUGHTS ON AN 

 EVOLUTIONARY PHILOSOPHY 



This discussion will close with some thoughts on how our 

 present knowledge of evolution could affect our philosophy of 

 life. The point of view adopted here is entirely personal, and 

 I make no apologies for it. The facts upon which it is based 

 are derived from a variety of sources, and most of the ideas have 

 already been expressed by a number of other writers. 



When we apply the concepts of evolution to our own past, 

 we quickly realize that man is the product of two different kinds 

 of evolution. Our bodies have evolved in the same way as those 

 of other mammals, particularly primates. As mentioned above, 

 the fossil record of man's ancestors is gradually being laid bare. 

 We now can reconstruct with some assurance the way in which 

 our ancestors first started to walk erect, to use tools and fire, 

 and to hunt game in groups or primitive societies. We are sure 

 that the size of the human brain increased gradually, as did 

 also man's ability to make better tools. If, therefore, we con- 

 sider only our bodies, we must conclude that we are no more 

 than large apes that walk erect and have unusually large brains. 



But our present way of life does not depend only upon our 

 bodies and our brain power. Our minds and our social organ- 

 ization contribute far more to human nature than our bodies. 

 Furthermore, our minds and social behavior, although based 

 upon the foundation of our biological, genetic heredity, must 

 nevertheless be reconstructed in each generation by learning. 

 From our parents, our teachers, and from the leaders of our 

 society we acquire a vast store of cultural heredity, which has 



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