146 THE ANTIQUITY OF MAN 
aspect the genial pit is almost filled up, but there is still 
a remnant to be seen (fig. 49). The muscles of the 
tongue arise from areas corresponding to those in the 
gorilla (<^, b, c). The next section in fig. 49 shows the 
region of the chin in a representative of a modern 
primitive race — a native of New Caledonia, in the Pacific 
Archipelago. The upper and lower borders of the lower 
jaw are nearly equally prominent in the anterior or 
symphyseal region ; indeed, the chin eminence is slightly 
developed. On the posterior aspect of this particular 
mandible there is a trace of the genial pit — a simian trait ; 
but there are also present below the pit special minute 
projections of bone — tubercles or spines from which the 
special muscles of the tongue arise (see fig. 49, a^ b). 
Those tubercles or spines are absent in mandibles of the 
Neanderthal type. Lastly, the region of the chin of a 
man of modern European origin is shown. The lower 
border is the more prominent ; there is here a well- 
developed chin eminence. On the posterior aspect there 
is no trace of the genial pit ; the genio-glossus muscles 
(a) arise from two projecting points or spines of bone. 
We cannot account satisfactorily for the various 
structural features exhibited by the series of specimens 
just described unless we suppose the simian condition 
to be the older, the ancestral form, and the others — the 
Neanderthal and the modern — to represent modifications 
of the simian form. There can be no doubt that, in the 
region of the chin. Neanderthal man retains a simian 
condition to a greater extent than does the mandible of 
the modern type of man. When we seek to explain 
these changes on a functional or physiological basis we 
proceed on the belief that these changes have been 
brought about by the interaction of at least two factors. 
In the first place, the teeth have become smaller ; retro- 
gression in the size of the teeth leads to the front or 
incisor teeth receding backwards in the mouth, leaving 
the nose above and the chin below more prominent. 
Undoubtedly another process has been at work. The 
lower border of the mandible, in the region of the chin 
