marvellous fact that the embryos of a man, dog, seal, bat, reptile,
etc., can at first hardly be distinguished from each other. In order to
understand the existence of rudimentary organs, we have only to suppose
that a former progenitor possessed the parts in question in a perfect
state, and that under changed habits of life they became greatly
reduced, either from simple disuse, or through the natural selection of
those individuals which were least encumbered with a superfluous part,
aided by the other means previously indicated.
Thus we can understand how it has come to pass that man and all other
vertebrate animals have been constructed on the same general model, why
they pass through the same early stages of development, and why they
retain certain rudiments in common. Consequently we ought frankly to
admit their community of descent: to take any other view, is to admit
that our own structure, and that of all the animals around us, is a
mere snare laid to entrap our judgment. This conclusion is greatly
strengthened, if we look to the members of the whole animal series, and
consider the evidence derived from their affinities or classification,
their geographical distribution and geological succession. It is only
our natural prejudice, and that arrogance which made our forefathers
declare that they were descended from demi-gods, which leads us to
demur to this conclusion. But the time will before long come, when it
will be thought wonderful that naturalists, who were well acquainted
with the comparative structure and development of man, and other
mammals, should have believed that each was the work of a separate act
of creation.
CHAPTER II.
ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME LOWER FORM.
Variability of body and mind in man Inheritance Causes of
variability Laws of variation the same in man as in the lower
animals Direct action of the conditions of life Effects of the
increased use and disuse of parts Arrested
development Reversion Correlated variation Rate of increase Checks to
increase Natural selection Man the most dominant animal in the
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