| The abrupt manner in which whole groups of species suddenly appear in certain formations, has been urged by several
for instance, by Agassiz, Pictet, and
→Sedgwick—
as a fatal objection to the belief in the transmutation of species. If numerous species, belonging to the same genera or families, have really started into life
at once, the fact would be fatal to the theory of
→descent with slow modification
through natural selection. For the development
→of
a group of forms, all of which
descended from some one progenitor, must have been an extremely slow process; and the
must have lived long
before their modified descendants. But we continually
the perfection of the geological record, and falsely infer, because certain genera or families have not been found beneath a certain stage, that they did not exist before that stage. In all cases positive palæontological evidence may be implicitly trusted; negative evidence is worthless, as experience has so often shown. We continually forget how large the world is, compared with the area over which our geological formations have been carefully examined; we forget that groups of species may elsewhere have long
and have slowly
before they invaded the ancient archipelagoes of Europe and
the United States. We do not make due allowance for the
intervals of
which have
elapsed between our consecutive formations,— longer perhaps in
cases than the time
|
