30 PHYSICAL BASIS OF CIVILIZATION 



offspring, and we who are alive to-day must there- 

 fore be descended from those who quickly resorted 

 to the erect position. 



Variations tending to the shortening of the arms, 

 to modifications in the fibula, tibia, astragalus, 

 calcaneum, in the muscular attachments to these 

 bones, in the nerves operating them, and in various 

 other structures more or less related to the upright 

 attitude, must have begun to be naturally selected 

 shortly after the occurrence of the changes in the 

 entocuneiform bone, for it was this event which 

 gave them survival value. These changes, however, 

 may have taken many generations to attain that 

 perfect adaptation to the upright attitude in which 

 they are found to-day. 



In this connection it is interesting to note the 

 reports of naturalists who have sojourned in dis- 

 tricts where monkeys abound. Of the anthropoids 

 when in the upright attitude, they tell that these 

 frequently walk on the knuckles of their posterior 

 pair of hands, and at other times on the outside edges. 

 Attempts to walk on their palms would obviously 

 necessitate the outstretching of the fingers in front 

 and of the thumbs at right angles. In this position 

 slight irregularities in the surface of the ground, such 

 as tend to deflect the weight of the body in the direc- 

 tion of the center line between the feet, would then, 

 at the points where the thumbs join the hands, in- 

 crease the strain to an extent, making liability to 

 dislocations and fractures unavoidable. This cir- 



