62 EVOLUTION OF MAMMALIAN MOLAR TEETH 



till out all the spaces between them, so that a square lower tooth 

 would abut against a square upper tooth, as in J, and this was done 

 by simply adding a heel to this tooth. Now, what would that heel 

 come against in /? It would come against the anterior cusp of the 

 lower triangle ; therefore that cusp had to be removed, so when 

 the upper heel was developed this lower cusp was removed and the 

 lower molar, which had six cusps, presented only five ; then the 

 second lingual cusp was pushed forward as in J, and the tooth 

 was transformed into a quadritubercular molar. 



Evidence that the Upper Human Molars were Triangular. 



How do we know that is so i We have some conclusive evi- 

 dence of it in other animals of the group to which man belongs. 

 Beginning with the lemurs, the lowest type of monkeys, and entirely 

 separate in many respects from the higher types, we find almost 

 without exception that the upper teeth are triangular, there being 

 no posterior cusp, so that Fig. 40, Xo. 9, accurately represents a tooth 

 of the lemurs, and it also represents the tooth of the true monkeys 

 which we find in the Eocene period ; in other words, all monkeys or 

 all primates (the group to which man belongs) had at the outset 

 this triangular upper molar. Then earlier or later in the Eocene or 

 Miocene the spur began to be developed which transformed a three- 

 cusp tooth or a triangular tooth into a quadritubercular tooth. That 

 spur became enlarged and finally, in civilized races of men, we have 

 a tooth of this form as the prevailing type of tooth. These stages 

 are shown in Fig. 40. 



Xow, we might say that the evidence is not perfectly satisfactory, 

 because we have no positive reason for believing that the human 

 teeth were derived from such a type as this ; they may have come 

 along another line of descent, and for that reason we have to show 

 here, through the kindness of one of the members of the dental pro- 

 fession in this city, the teeth of an Eskimo (Fig. 40, Xo. 11), which, 

 as Professor Cope has pointed out, differ from the teeth of all negroes, all 

 Indians, and all the lower races of men, in presenting in a much 

 clearer manner the primitive triangular arrangement of the cusps that 

 characterize the lemurs. A friend has just been telling us what 

 very few of us knew, that the Eskimos do not chew their food : 

 they simply swallow 7 it whole or gulp it down ; and their food 

 consists largely of blubber. Blubber does not form much resistance 

 to the teeth, and, whether as a mechanical or an inherited effect 

 of the lack of resistance of soft food through many generations 



O v C? 



of blubber-eating Eskimos or not, the teeth of these Eskimos are 



