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THE AMERICAN MUSEUM JOURNAL 



tlic fncc and its bony substrncture, were 

 tlie downward and outward growtb of 

 tlie nose and tbe forward growtli of tlic 

 chin. 



Tlie evolution of the chin has «iivcn 

 rise to an extensive literature. Some 

 writers ascribe its existence to the ex- 

 cessive develo]unent of the genioglossus 

 muscle, which runs from the hinder 

 surface of the chin into the lower part 

 of the tongue and which throws the 

 tongue into the rapidly shifting posi- 

 tions assumed in articulate speech. 

 Other writers ascribe the outgrowth of 

 the bony chin to the withdrawal hack- 

 ward of the dental arch, to the in- 

 creased pressure in the chin I'cgion. and 

 to the turning outward of tlu' lower 

 rim of the jaw. Others regard the 

 chiji. like the nose, as a direct out- 

 growth, of no great functional ini](oi'- 

 tance, but liidxcd in some way with tlu- 

 progressive improvement, according to 

 human standards, in the a])])earance of 

 the whole face. The ])i-esent writer 

 has sfuight to connect all these changes, 

 including the reduction in size of the 

 canines and bicuspids, with a jirofound 

 change of food habits from the om- 

 nivorous-frugivorous habits of forest- 

 living apes to the predatory carnivorous 

 habits of plains-living men. 



The profound disturbances and re- 

 adjustments in the brain, brain case, 

 and face were accompanied by equally 

 far-reaching changes in the backbone 

 and in the pelvis and in the bones and 

 muscles of the limbs. The forearms. 



no longer used in the stooping postui'e, 

 shortened, while the legs rapidly length- 

 ened, so that men very early l)ecame 

 fast runners on the open plains. 



in conclusion, if we compare the 

 skull of a young anthropoid ape with 

 that of a young human being we shall 

 find that every bone in the ape skull 

 may readily he identified in a slightly 

 different foriu in the human skull; the 

 number and kinds of teeth are the 

 same, both in the milk and ]tennanent 

 dentitions, and even the crown-pat- 

 tt'rns of the molar and l)icus|)id teeth 

 ari' fundamentally similar in primitive 

 apes and men. In spite of all the read- 

 justments following the assumption of 

 the fully upi'ight gait and the change 

 in food habits, the ditfei'eiices be- 

 tween the ])riuiiti\e ape skull and the 

 human .-kull ai'e esseutially ditferences 

 of pi'oport ion and of degree rather than 

 of kind. 



l-'i'oin the paheontological viewpoint 

 these numerous and fundamental re- 

 semblances can only mean that li\ing 

 apes and men have evolved from a re- 

 mote and as yet undiscovered common 

 ancestor that lived perhaps in the mid- 

 dle period of the Age of ^Mammals. 

 I believe also that the living apes, lie- 

 cause they have stayed in the ancestral 

 habitat, have retained the greater part 

 of the ancestral man-ape characters, 

 and that the ancestral pattern of the 

 human face may still be seen in a little 

 changed state in the faces of young 

 female gorillas and chimpanzees. 



