Then, whoever concludes that these primitive makers of rude flint
axes and knives were the ancestors of the better workmen of the
succeeding stone age, and these again of the succeeding artificers in
brass and iron, will also be likely to suppose that the _Equus_ and
_Bos_ of that time were the remote progenitors of our own horses and
cattle. In all candor we must at least concede that such
considerations suggest a genetic descent from the drift period down
to the present, and allow time enough--if time is of any account--for
variation and natural selection to work out some appreciable results
in the way of divergence into races or even into so-called species.
Whatever might have been thought, when geological time was supposed
to be separated from the present era by a clear line, it is certain
that a gradual replacement of old forms by new ones is strongly
suggestive of some mode of origination which may still be operative.
When species, like individuals, were found to die out one by one, and
apparently to come in one by one, a theory for what Owen sonorously
calls "the continuous operation of the ordained becoming of living
things" could not be far off.
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