EVOLUTION OF MAN 



MAN 



231 



GORILLA 



Incisors 



Incisors 



FIG. 11.6. Upper dental arches of man and gorilla. (Modified from Wei- 

 denreich. Apes, Gianfs, and Man, University of Chicago Press, 1946, p. 9.) 



shelf" is lacking in men, both Homo sapiens and his predecessors, and in 

 many, at least, of the Dryopithecinae (e.g.. Proconsul, Fig. 1 1 .7 ) . 



Another result of the small teeth in modern Homo sapiens is that the 

 tooth row is short, as compared to that of apes and some of the earlier 

 hominids. The longer tooth row possessed by these latter causes the face 



FIG. 11.7. Lower jaws of chimpanzee (left) and of Proconsul (right). (From Le Gros Clark, 

 Hisfory of the Primates, British Museum [Natural History], 1949, p. 59.) 



to protrude into a sort of muzzle — to be prognathous. The face of modern 

 Homo sapiens, on the other hand, does not project in this fashion; the 

 profile is more nearly vertical, or orthognathous. 



In apes and earlier hominids with their long tooth rows the upper edge 

 of the lower jaw extends forward further than does the lower — there is no 



