THE EVOLUTION OF MAN 433 



structure of the shoulder girdle, which profoundly in- 

 fluenced subsequent developments. Thus the coracoid 

 bone, so prominent in birds, became reduced to a mere 

 rudiment, forming in man the coracoid process of the 

 scapula (shoulder blade). 



8. From the primitive marsupials the most natural Origin of the 

 step is to some form of tree-living insectivore, such a Pnmates 

 creature as the Tupaia or tree shrew of the Oriental 

 Region. At about this stage the bats branched off, tak- 

 ing to the air and thus losing all chance of developing 

 tool-making hands. From the primitive arboreal in- 

 sectivore, somewhere about the beginning of the Ter- 

 tiary age, we may derive the early Primates, more or 



less lemurlike forms. It may be worth while to ask why 

 we have omitted all the other great groups of mammals 

 from the possible line of descent. The answer is, that 

 each one of them has specialized in a direction wholly 

 divergent from a possible human stem. Thus the Ro- 

 dents, in their teeth, and the Ungulates, in their feet, 

 have gone to extremes which preclude the subsequent 

 development of the human type of dentition or digital 

 structure. Parts lost will not be regained, and parts 

 extremely specialized and modified will not return to a 

 relatively primitive condition. 



9. From the long-nosed Primates, or lemurs, we may Develop- 

 readily pass to the true monkeys and monkeylike forms. ^y S 

 Here we come to a division, for although lemurlike ani- and man 

 mals were formerly spread over both hemispheres, the 

 monkeys developed quite distinct types on the two 



sides of the world. Man, in his structure, is related to 

 the Old World monkeys, not to those of South and 

 Central America. Thus the traditional Old World ori- 

 gin of mankind is confirmed by zoological researches. 

 No existing type of monkey can be said to resemble very 



