415. Also, Isidore Geoffroy on the American monkeys and other kinds,
Hist. Nat. Gen. vol. ii. 1859, pp. 216, 243. Eschricht, ibid. s. 46,
55, 61. Owen, Anatomy of Vertebrates, vol. iii. p. 619. Wallace,
Contributions to the Theory of Natural Selection, 1870, p. 344.)
It must not be supposed that the resemblances between man and certain
apes in the above and in many other points such as in having a naked
forehead, long tresses on the head, etc., are all necessarily the
result of unbroken inheritance from a common progenitor, or of
subsequent reversion. Many of these resemblances are more probably due
to analogous variation, which follows, as I have elsewhere attempted to
shew (10. Origin of Species, 5th edit. 1869, p.194. The Variation of
Animals and Plants under Domestication, vol. ii. 1868, p. 348.), from
co-descended organisms having a similar constitution, and having been
acted on by like causes inducing similar modifications. With respect to
the similar direction of the hair on the fore-arms of man and certain
monkeys, as this character is common to almost all the anthropomorphous
apes, it may probably be attributed to inheritance; but this is not
certain, as some very distinct American monkeys are thus characterised.
Although, as we have now seen, man has no just right to form a separate
Order for his own reception, he may perhaps claim a distinct Sub-order
or Family. Prof. Huxley, in his last work (11. An Introduction to the
Classification of Animals, 1869, p. 99.), divides the primates into
three Sub-orders; namely, the Anthropidae with man alone, the Simiadae
including monkeys of all kinds, and the Lemuridae with the diversified
genera of lemurs. As far as differences in certain important points of
structure are concerned, man may no doubt rightly claim the rank of a
Sub-order; and this rank is too low, if we look chiefly to his mental
faculties. Nevertheless, from a genealogical point of view it appears
that this rank is too high, and that man ought to form merely a Family,
or possibly even only a Sub-family. If we imagine three lines of
descent proceeding from a common stock, it is quite conceivable that
two of them might after the lapse of ages be so slightly changed as
still to remain as species of the same genus, whilst the third line
might become so greatly modified as to deserve to rank as a distinct
Sub-family, Family, or even Order. But in this case it is almost
certain that the third line would still retain through inheritance
numerous small points of resemblance with the other two. Here, then,
would occur the difficulty, at present insoluble, how much weight we
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