EVOLUTION OF THE HUMAN FACE 



38^ 



liave a sliarply ivtreating" foreliead l)iit 

 a domelike one and a relatively very 

 large brain case. Altliough space i? lack- 

 ing to discuss tliis (|uestion, I may Ix' 

 permitted to record my conviction that 

 this inference is quite wrong and that 

 the human I'acc lias been derived from 

 large, powerful apelike forms witli 

 heavy jaws, massive jaw muscles and a 

 sharply retreating forehead. 



The evolution of the human fore- 

 head is well suggested if we examine a 

 series of skulls. In an adult chim- 

 panzee skull the forehead is very low 

 and there are heavy ridges over the 

 eyes. In the skull of an Australian 

 black man also the forehead is low and 

 there are well-defined brow ridges. In 

 a modern European skull the forehead 

 is high and the brow ridges are lack- 

 ing. In the shape of the forehead the 

 extinct ape-man of Java was almost ex- 

 actly intermediate between the chim- 

 panzee and the lowest known human 

 forehead, that of the Neanderthal race 

 of the Old Stone age. The brain case 

 accordingly has progressively deepened 

 in its vertical diameter, as we pass up- 

 ward from an apelike stage. 



These changes in the contour of the 

 brain case merely reflect the more fun- 

 damental changes in the form of the 

 brain which in the higher types be- 

 comes excessively voluminous and, as it 

 were, presses out the forehead and 

 skull top in all directions so that in 

 short-headed races of men the head Ite- 

 eoines almost spherical in form. 



Every part of the bony face of Pri- 

 mates has no doubt l:»cen molded in the 

 long run by the action of the facial 

 muscles that press u[)on it. The parti- 

 tion of bone behind the eyes, for ex- 

 ample, has grown downward and out- 

 ward between the eye and its muscles 

 which lie in front of it, and the power- 

 ful jaw muscle (temporal) lying l)e- 



liiiid it. Tlie ch(.'ek bone has been deep- 

 ened to give a strong support for the 

 outer jaw muscle (masseter). The 

 nasal bones have perhaps been molded 

 to some extent 1)y the muscles on either 

 side of them. 



In comparing men and apes one of 

 the greatest differences is seen in the 

 form of the front part of the up]X'r 

 jaw. which is associated with the 

 marked differences in the form of the 

 lips already alluded to, and with cer- 

 tain no less important differences in the 

 character of the teeth and in the move- 

 ment of the lower jaw. It seems very 

 well established that as the primitive 

 ape-men passed from the semi-erect to 

 the fully erect posture, and as the rap- 

 idly expanding brain case became bal- 

 anced at the top of the progressively 

 up-tilted backbone, the whole front part 

 of the jaws and lips was drawn back- 

 ward beneath the overgrowing front 

 part of the brain case; meanwhile the 

 lower jaw and the whole head increased 

 greatly in vertical height, but short- 

 ened equally in fore-and-aft length ; 

 the width across the brain case in- 

 creased, the sockets of the lower jaws 

 moved apart and the opposite halves 

 of the jaws became sharply inclined to- 

 ward each other, so that the front teeth 

 were all drawn backward; the palate 

 and the lower jaw were thus shortened, 

 and the dental arches assumed an are1i- 

 like curve, the ci-owding of the front 

 ])art of the jaw hcing ])artly associated 

 ■with the mai'keil I'cduction in size of 

 the canine and pix'inolar teeth. 



A multitude of minor changes and 

 readjustments took ])lace at this critical 

 time, but they were nearly all the direct 

 result of the general tendency to shorten 

 the face and di'aw it inward beneath 

 the overgrowing, forward expansion of 

 the brain case. Among other important 

 consequences of this general retreat of 



