OUR FACE FROM FISH TO MAN 



the system of the ductless glands which has so 

 profound an effect upon growth and development 

 was affected in innumerable ways and differently 

 in different individuals and races. Thus we begin 

 to sense the complexity of the factors influencing 

 the emergence of the typical human face from a 

 primitive anthropoid type. 



Wliatever the causes may have been, the evi- 

 dence indicates that, starting with a face not dis- 

 similar to that of an immature female chimpanzee 

 (Fig. 40B), the forehead rapidly became larger, 

 the incisor teeth became less inclined, more vertical 

 and smaller in size, the canine teeth diminished 

 in size and in such a way that the tip of the lower 

 one finally passed behind the front edge of the 

 upper canine; the premolars and molars also 

 decreased in fore and aft diameter. In addition 

 to the reduction and backward displacement of 

 the teeth there was a positive outgrowth of the 

 bony chin, which possibly on account of the early 

 development of the tongue could not retreat fur- 

 ther backward. The later stages of this process 

 may be reconstructed by comparing the faces of 

 different races, from the projecting muzzles, very 



large mouth, broad flat nose and retreating chin 



76 



