THE HUMAN BACKGROUND 445 



tively static character of Man's nature may possibly constitute 

 a crucial handicap to indefinite human progress. One may be a 

 confirmed optimist and still admit that the increasing momentum 

 of the stupendous cultural advance during the past century is to- 

 day taxing the adjustment capacity — the adaptability — of the 

 human biological heritage. Surely, Man must study himself more 

 intensively. 



And so we may appropriately reiterate what was stated on an 

 early page : the most pregnant thought from the study of biology 

 in general and Man's past in particular is the unity of nature — 

 the oneness of life — based on the ever -increasing background of 

 knowledge which "robs life of none of its mystery but rather serves 

 to link it securely with the larger mystery of the universe and the 

 Infinite back of it all." But Man, though one with all living beings, 

 has the unique and all-important power consciously to study the 

 ways, to direct the forces of nature, and to adapt himself to them. 

 The knowledge of Man's physical development through the ages 

 in no wise minimizes the other aspects of his nature on whose 

 origin biology is silent, and which constitute the enormous gap 

 that separates him from the beasts. When the grandeur of this 

 view of life to which biology leads is appreciated to the full, no 

 reassurance is necessary of Man's commanding position — his op- 

 portunities and his responsibilities. 



