xxiv. 8 TEETH AND JAWS 639 



there is great variation in these patterns, both in man and apes. Little 

 can be said therefore about a single tooth, but the proportion of 

 molars with four cusps and a 

 -f- pattern is higher in man than in 

 apes (Fig. 415). The last molar (wis- 

 dom tooth) is smaller than the others 

 in man, but not in modern apes. 

 There are, however, many signs of 

 possible ape-like ancestry in our 

 teeth; for instance the canine has 

 a long root and erupts late. 



The lower jaw of man is less 

 shortened than the upper; whereas 

 in apes it is strengthened by a 

 'simian shelf of bone on its inner 

 side, in man this strengthening is on 

 the outside, making the chin. The 

 jaw is less massive in man than in 

 apes, especially its posterior ramus; 



Fig. 414. Mandibular molar patterns 

 in the Liberian chimpanzee and human 

 dentition. The chief distinguishing 

 feature between Y and + patterns is the 

 relationship of cusps 2 and 3 to each 

 other. In the Y pattern they are in 

 contact, in the + pattern they are 

 separated by cusps 1 and 4. 



B, buccal; D, distal; L, lingual; M, mesial; 

 1 protoconid; 2, metaconid; 3, hypoconid; 

 4, entoconid; 5, hypoconulid. (After Schu- 

 man and Brace.) 



Chimp. 



Pecos 



Europ. 

 white 



others 



Fig. 415. Proportions of the various mandibular molar patterns found in 

 Chimpanzees, Pecos Indians, and European Whites. (After Schuman and 



Brace.) 



the muscles for moving it are less powerful. Correlated with this weaken- 

 ing of the jaw has been a rounding of the surface of the skull. Occipital 

 and temporal crests for the attachment of the neck and jaw muscles are 

 well developed in the male gorilla, suggested in other apes, but absent in 

 man. The brow ridges, also characteristic of the apes, are large masses 



