OUR FACE FROM FISH TO MAN 



further development of the temporal fossa and 

 especially the dominance of the inferior maxillary 

 or dentary bone of the lower jaw. To these 

 progressive pro-mammals man can render thanks 

 for the differentiation of his dentition into incisors, 

 canines, premolars and molars, and apparently 

 he can also thank them for the reduction of the 

 numerous successional teeth to two sets, corre- 

 sponding to the milk teeth and the permanent set. 



The earliest mammals invented one of the most 

 useful features of man's skull by eliminating from 

 the masticatory apparatus all the elements lying 

 behind the dentary and by establishing the 

 temporo-mandibular joint. They also cast off 

 the reptilian prefrontal, postfrontal and postorbital 

 bones and cleared the way for the final simplifica- 

 tion of the bony scaffolding of the face. 



To the earliest primates, well schooled in 

 arboreal life, man owes the first steps in the 

 glorification of the eyes, which become increasingly 

 dominant. These still lowly but thrifty forebears 

 made good the loss of the reptilian postorbital 

 bar by elaborating a new one from conjoining pro- 

 cesses from the frontal and jugal (or malar) bones. 



But still greater was our debt to the arboreal 



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