naturalist, would have been classed amongst the Quadrumana, as surely
as the still more ancient progenitor of the Old and New World monkeys.
The Quadrumana and all the higher mammals are probably derived from an
ancient marsupial animal, and this through a long line of diversified
forms, from some amphibian-like creature, and this again from some
fish-like animal. In the dim obscurity of the past we can see that the
early progenitor of all the Vertebrata must have been an aquatic
animal, provided with branchiae, with the two sexes united in the same
individual, and with the most important organs of the body (such as the
brain and heart) imperfectly or not at all developed. This animal seems
to have been more like the larvae of the existing marine Ascidians than
any other known form.
The high standard of our intellectual powers and moral disposition is
the greatest difficulty which presents itself, after we have been
driven to this conclusion on the origin of man. But every one who
admits the principle of evolution, must see that the mental powers of
the higher animals, which are the same in kind with those of man,
though so different in degree, are capable of advancement. Thus the
interval between the mental powers of one of the higher apes and of a
fish, or between those of an ant and scale-insect, is immense; yet
their development does not offer any special difficulty; for with our
domesticated animals, the mental faculties are certainly variable, and
the variations are inherited. No one doubts that they are of the utmost
importance to animals in a state of nature. Therefore the conditions
are favourable for their development through natural selection. The
same conclusion may be extended to man; the intellect must have been
all-important to him, even at a very remote period, as enabling him to
invent and use language, to make weapons, tools, traps, etc., whereby
with the aid of his social habits, he long ago became the most dominant
of all living creatures.
A great stride in the development of the intellect will have followed,
as soon as the half-art and half-instinct of language came into use;
for the continued use of language will have reacted on the brain and
produced an inherited effect; and this again will have reacted on the
improvement of language. As Mr. Chauncey Wright (1. On the Limits of
Natural Selection, in the North American Review, Oct. 1870, p. 295.)
has well remarked, the largeness of the brain in man relatively to his
body, compared with the lower animals, may be attributed in chief part
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