conditions certainly play an important part in exciting organic changes
of many kinds.
Through the means just specified, aided perhaps by others as yet
undiscovered, man has been raised to his present state. But since he
attained to the rank of manhood, he has diverged into distinct races,
or as they may be more fitly called, sub-species. Some of these, such
as the Negro and European, are so distinct that, if specimens had been
brought to a naturalist without any further information, they would
undoubtedly have been considered by him as good and true species.
Nevertheless all the races agree in so many unimportant details of
structure and in so many mental peculiarities that these can be
accounted for only by inheritance from a common progenitor; and a
progenitor thus characterised would probably deserve to rank as man.
It must not be supposed that the divergence of each race from the other
races, and of all from a common stock, can be traced back to any one
pair of progenitors. On the contrary, at every stage in the process of
modification, all the individuals which were in any way better fitted
for their conditions of life, though in different degrees, would have
survived in greater numbers than the less well-fitted. The process
would have been like that followed by man, when he does not
intentionally select particular individuals, but breeds from all the
superior individuals, and neglects the inferior. He thus slowly but
surely modifies his stock, and unconsciously forms a new strain. So
with respect to modifications acquired independently of selection, and
due to variations arising from the nature of the organism and the
action of the surrounding conditions, or from changed habits of life,
no single pair will have been modified much more than the other pairs
inhabiting the same country, for all will have been continually blended
through free intercrossing.
By considering the embryological structure of man, the homologies which
he presents with the lower animals, the rudiments which he retains, and
the reversions to which he is liable, we can partly recall in
imagination the former condition of our early progenitors; and can
approximately place them in their proper place in the zoological
series. We thus learn that man is descended from a hairy, tailed
quadruped, probably arboreal in its habits, and an inhabitant of the
Old World. This creature, if its whole structure had been examined by a
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