WHOLE VOL. SKELETAL REMAINS OF EARLY MAN — HRDLICKA 355 



Relative proportions. — The relative proportions of the lower molars 



are readily expressed by the Crown Index Crown breadth x loo . 



Crown length 

 This index, as we proceed back in time, decreases gradually in man, 

 and from man to the lower primates. The remeasurement of the 

 teeth of early man gave values and indices which are reported in 

 detail on pages 356-360. 



The principal points brought out by the data are briefly as follows : 



1. As in absolute, so in relative size, the lower molars bear a general 

 definite correlation with time ; the greater their antiquity the greater 

 the relative length of the teeth and vice versa. 



2. The breadth (or stoutness) of the tooth in the course of man's 

 existence has shown but little change, much less than the length. 



3. The facts indicate that in man's precursors the lower molars were 

 longer but probably only slightly stouter than they are in man of today. 



4. Concerning the lower molars in present man, it is safe to regard 

 as primitive or phylogenetically inferior a tooth that is absolutely 

 large, or one that is relatively long, giving a low crown index. 



The progressive shortening of the human lower molars must have 

 been concomitant, it is plain, with a progressive shortening of the 

 jaws, though the change was primarily in the teeth and not in the 

 jaws ; had it been in the latter there would in all likelihood be observ- 

 able a compensatory increase in the breadth (stoutness) of the teeth 

 and the M3 would be least affected, which is not the case. 



Some additional observations of interest were possible on the 

 M3 in the remains of early man. With very few exceptions this 

 tooth shows no degeneracy or alteration such as are common in 

 modern man. As may be seen in the table on the " Size of the lower 

 molars in early man " (p. 354) there is a progression in the size of 

 the teeth from before backward in the jaw of Piltdown, though in 

 this case we have only the more anterior two molars ; in the jaw of 

 Mauer, where the M2 is larger than M i and M3 larger than M2 ; 

 in both the jaws of Ehringsdorf, where M2 is larger than Mi, 

 though in the adult the M3 is smaller than either of the preceding 

 teeth ; and in the Mousterian youth, where we have a decided pro- 

 gression in the size of the three molars from before backward. In 

 all the rest of the teeth, the M2 averages slightly less than the Mi, and 

 the M3 is smaller than the M2, except in the Predmost teeth where the 

 M3 is larger than the M2, equalling the Mi. Individually, a progres- 

 sion from before backwards in the size of the three molars was 



