THE TEETH OF FOSSIL MAN 471 
tooth development of ancient races — of people who 
lived in the Neolithic, Bronze, or early Iron ages — 
is convinced that there has been a reduction in the 
molar development of the more highly civilised races. 
We do not know the exact means which has wrought 
this change in the human body, but we do see the 
order in which the teeth undergo reduction. It will 
be noted that in the English students the molar teeth 
diminish from first to third. In Eoanthropus and 
in the Heidelberg jaw, the reduction does not come 
in that order — almost the opposite. The second is 
larger than the first ; the third is also larger than the 
first, if equal to or perhaps smaller than the second. 
If we examine the molar teeth of such primates as the 
gorilla and baboon, in which the teeth reach the zenith 
of dental development, the order is exactly the reverse 
of that found in modern highly civilised races. The 
lower molars increase in size from first to third. It 
will be remembered that we fixed the zero point in 
the dental series between the last premolar tooth and 
first molar. Increase or reduction commences in the 
teeth furthest removed from the zero point. In the 
molar series the third or last is the one to show the 
initial change, whether it be retrogressive or progressive 
in nature. 
The anatomists of a former generation were inclined 
to rely on the relative development of the molar teeth as 
a guide to the affinity of animal forms. There can be no 
doubt as to the close structural relationships between the 
gorilla and chimpanzee, yet as regards the degree of 
molar development they represent opposite conditions. 
In the average gorilla the third molar is the largest of the 
series ; in the average chimpanzee it is the smallest. In 
one there is a progressive molar development ; in the other 
there is a retrograde one. If we recognise a state in 
which the two last molars of the lower jaw are of about 
the same size, as the normal or " plenal " condition, then 
we may distinguish those dentitions in which the third 
molar is the largest of the series, as in the gorilla, as 
