the individuals in an intermediate condition would have been miserably
ill-fitted for progression. But we know (and this is well worthy of
reflection) that the anthropomorphous apes are now actually in an
intermediate condition; and no one doubts that they are on the whole
well adapted for their conditions of life. Thus the gorilla runs with a
sidelong shambling gait, but more commonly progresses by resting on its
bent hands. The long-armed apes occasionally use their arms like
crutches, swinging their bodies forward between them, and some kinds of
Hylobates, without having been taught, can walk or run upright with
tolerable quickness; yet they move awkwardly, and much less securely
than man. We see, in short, in existing monkeys a manner of progression
intermediate between that of a quadruped and a biped; but, as an
unprejudiced judge (75. Prof. Broca, La Constitution des Vertebres
caudales; La Revue d Anthropologie, 1872, p. 26, (separate copy).)
insists, the anthropomorphous apes approach in structure more nearly to
the bipedal than to the quadrupedal type.
As the progenitors of man became more and more erect, with their hands
and arms more and more modified for prehension and other purposes, with
their feet and legs at the same time transformed for firm support and
progression, endless other changes of structure would have become
necessary. The pelvis would have to be broadened, the spine peculiarly
curved, and the head fixed in an altered position, all which changes
have been attained by man. Prof. Schaaffhausen (76. On the Primitive
Form of the Skull, translated in Anthropological Review, Oct. 1868,
p. 428. Owen ( Anatomy of Vertebrates, vol. ii. 1866, p. 551) on the
mastoid processes in the higher apes.) maintains that the powerful
mastoid processes of the human skull are the result of his erect
position; and these processes are absent in the orang, chimpanzee,
etc., and are smaller in the gorilla than in man. Various other
structures, which appear connected with man s erect position, might
here have been added. It is very difficult to decide how far these
correlated modifications are the result of natural selection, and how
far of the inherited effects of the increased use of certain parts, or
of the action of one part on another. No doubt these means of change
often co-operate: thus when certain muscles, and the crests of bone to
which they are attached, become enlarged by habitual use, this shews
that certain actions are habitually performed and must be serviceable.
Hence the individuals which performed them best, would tend to survive
in greater numbers.
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