98 EVOLUTION 



below the waves. The Pithecanthropus bones are mixed 

 with those of animals of the Pliocene Period, and are 

 generally referred to the middle of the Tertiary ; though 

 it seems more conformable to later human development 

 to put them later. 



This discovery amply confirmed the view of man's 

 evolution which had already been taken on the ground of 

 his vestigial organs, his embryonic development, and his 

 close anatomical resemblance to the ape. Man and the 

 anthropoid ape correspond in every organ, apart from 

 slight differences in the ribs and sex organs. I will take 

 only one instance from anatomy to show how the 

 relationship stands. The teeth have a curious evolu- 

 tionary value. They originated in the mouth of the 

 primitive shark by a hardening and sharpening of the 

 prickles on the shagreen plate that lined the mouth. 

 The crushing of shell-fish, etc., " selected " the prickles 

 until they developed into teeth, lining the whole of the 

 palate (as we find them in the young shark). It was 

 further due to selection that the teeth on the edges of 

 the jaws (the most useful) were strengthened, and the 

 others died away. With changes in diet the teeth 

 degenerated, and our ancestors have been shedding 

 them along the path of our evolution for ages. The 

 earliest lemurs had forty-four teeth, the black lemurs 

 forty, the higher lemurs thirty-six, and we and all the 

 Old World apes have only thirty-two. But amongst the 

 lower races and the anthropoid apes we sometimes find 

 thirty-six teeth, and on the other hand, the higher races 

 tend to lose four more teeth (the " wisdom-teeth "), and 

 the same number (twenty-eight) is sometimes found in 

 the highest apes. We are shedding in fours the teeth of 

 our remote ancestors, and some equally remote genera- 

 tion of human beings will probably find itself toothless. 

 But the more interesting point is to speculate we 



