THE TEETH OF FOSSIL MAN 465 
173, B). In that illustration it will be seen that when 
the lower jaw is closed the sharp-sided pyramidal crown 
of the upper canine sinks into the V-shaped interval 
formed by the adjacent crowns of the lower canine and 
first premolar teeth, A pointed upper canine necessitates 
a cutting margin on the first lower premolar tooth. The 
canines of the anthropoid are shaped so as to serve 
as particularly stout shears. In man their shape and 
purpose are different. In him the canines serve almost 
the same purpose as incisor teeth. From its shape we 
infer that in the Piltdown race the canines were anthropoid 
in their action as well as in their form. 
A comparison of the human and anthropoid dentitions 
shown in fig. 171 helps us to understand how the 
anthropoid canines might be converted to a human form. 
In the human dentition the canines, both upper and lower, 
form part of the front series ; in anthropoids, although 
the canines are partially seen from the front, they are 
situated really in the lateral series. The transformation 
of canine teeth from the anthropoid to the human form 
apparently resulted from the change in their position — 
during their transference from the side to the front series. 
We have already seen that the evolution of modern 
human races must have been attended by a great reduction 
in the size of the incisor teeth and of that part of the 
jaws in which these teeth are implanted. I think it is 
probable, from the manner in which the Piltdown canine 
is worn, that the dental and maxillary reduction had set 
in, and that the canine was set, not as in apes, completely 
in the lateral series, but more in the front or incisor 
series. Hence in reconstructing the lower dentition in 
the Piltdown mandible I have given the canines an 
intermediate place between the side and front series 
(fig. 166, B). 
The discovery at Piltdown again draws attention 
to the size and growth of canine teeth in the anthro- 
poid apes — the animals which most closely resemble 
man in structure. Four stages in the development of 
canine teeth, four degrees in what may be named 
30 
