For as all the inhabitants of
each country are struggling together with nicely balanced forces, extremely
slight modifications in the structure or habits of one species would often
give it an advantage over others; and still further modifications of the
same kind would often still further increase the advantage, as long as the
species continued under the same conditions of life and profited by similar
means of subsistence and defence. No country can be named in which all the
native inhabitants are now so perfectly adapted to each other and to the
physical conditions under which they live, that none of them could be still
better adapted or improved; for in all countries, the natives have been so
far conquered by naturalised productions that they have allowed some
foreigners to take firm possession of the land. And as foreigners have
thus in every country beaten some of the natives, we may safely conclude
that the natives might have been modified with advantage, so as to have
better resisted the intruders.
As man can produce, and certainly has produced, a great result by his
methodical and unconscious means of selection, what may not natural
selection effect? Man can act only on external and visible characters:
Nature, if I may be allowed to personify the natural preservation or
survival of the fittest, cares nothing for appearances, except in so far as
they are useful to any being.
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