230 INTRODUCTION TO EVOLUTION 



row resembles a smoothly rounded parabola without sharp bends (Fig. 

 11.6); the incisors are small and the canines are not large and projecting as 

 they are in apes. In apes there is characteristically a gap or diastema 

 between the incisor teeth and the canine tooth on each side of the upper 

 jaw; the canine tooth of the lower jaw fits into this space when the mouth 



Lumbar curve 



lium 



GORILLA 



FIG. 11.5. Comparison of skull, vertebral column, 

 and pelvis of man and gorilla. (Redrawn from Boule 

 and Vallois, Fossil Men, The Dryden Press, 1957, 

 p. 74, by permission of Henry Holt & Co., Inc.) 



is closed. Homo sapiens, lacking the projecting canines, also lacks this 

 "simian gap" in the upper tooth row. 



In apes the first premolar teeth in the lower jaw have a cutting edge, are 

 sectorial. In Homo sapiens the first lower premolar does not have this 

 character. 



A characteristic of the jaw of modern apes related to the large incisor 

 and canine teeth is the development of a reinforcing ledge of bone ex- 

 tending backward from the symphysis of the jaw (Fig. 1 1.7). This "simian 



