why should
we doubt that variations we doubt that variations 1859 1860 1861 1866 |
we doubt that the variations or individual differences, which are 1869 |
not variations or individual differences, which are 1872 |
in any
way
useful to beings, under their excessively complex relations of life, would useful to beings, under their excessively complex relations of life, would 1859 1860 1861 |
useful to them under their extremely complex relations of life would 1866 |
beneficial would 1869 |
beneficial, 1872 |
be preserved, accumulated, and inherited? be preserved, accumulated, and inherited? 1859 1860 1861 |
occasionally occur, and then be preserved and accumulated by natural selection? 1866 |
be preserved and accumulated through natural selection, or the survival of the fittest? 1869 1872 |
Why, if Why, if 1859 1860 1861 1866 | If 1869 1872 |
man can by patience select variations
most most 1859 1860 1861 1866 | most 1869 1872 |
useful to
himself, should nature fail in selecting variations useful, himself, should nature fail in selecting variations useful, 1859 1860 1861 |
himself, should nature fail in preserving or selecting variations useful, 1866 |
him, why, 1869 1872 |
under changing
conditions conditions 1859 1860 1861 1866 |
and complex conditions 1869 1872 |
of life,
to her to her 1859 1860 1861 1866 |
should not variations useful to natures 1869 |
should not variations useful to nature's 1872 |
living
products? products? 1859 1860 1861 1866 |
products often arise, and be preserved or selected? 1869 1872 |
What limit can be put to this power, acting during long ages and rigidly scrutinising the whole constitution, structure, and habits of each creature,— favouring the good and rejecting the bad? I can see no limit to this power, in slowly and beautifully adapting each form to the most complex relations of life. The theory of natural selection, even if we looked
no
further further 1859 1860 | farther 1861 1866 1869 1872 |
than this, seems to me to
be in itself
probable. I have already recapitulated, as fairly as I could, the opposed difficulties and objections: now let us turn to the special facts and arguments in favour of the theory. |
On the view that species are only strongly marked and permanent varieties, and that each species first existed as a variety, we can see why it is that no line of demarcation can be drawn between species, commonly supposed to have been produced by special acts of creation, and varieties which are acknowledged to have been produced by secondary laws. On this same view we can understand how it is that in each
region where many species of a genus have been produced, and where they now flourish, these same species should present many varieties; for where the manufactory of species has been active, we might expect, as a general rule, to find it still in action; and this is the case if varieties be incipient species. Moreover, the species of the larger genera, which afford the greater
number of
|