The Descent of Man

teeth; but as they gradually acquired the habit
of using stones, clubs, or other weapons, for
fighting with their enemies or rivals, they
would use their jaws and teeth less and less. In
this case, the jaws, together with the teeth,
would become reduced in size, as we may feel
almost sure from innumerable analogous cases.
In a future chapter we shall meet with a closely
parallel case, in the reduction or complete disappearance
of the canine teeth in male ruminants,
apparently in relation with the development
of their horns; and in horses, in relation to
their habit of fighting with their incisor teeth
and hoofs.
In the adult male anthropomorphous apes, as
Rutimeyer (77. 'Die Grenzen der Thierwelt, eine
Betrachtung zu Darwin's Lehre,' 1868, s. 51.),
and others, have insisted, it is the effect on the
skull of the great development of the jawmuscles
that causes it to differ so greatly in
many respects from that of man, and has given