The Variation of Animals and Plants under Domestication, vol 1 | Page 9

of the Fittest. The term "natural selection" is
in some respects a bad one, as it seems to imply conscious choice; but

this will be disregarded after a little familiarity. No one objects to
chemists speaking of "elective affinity;" and certainly an acid has no
more choice in combining with a base, than the conditions of life have
in determining whether or not a new form be selected or preserved. The
term is so far a good one as it brings into connection the production of
domestic races by man's power of selection, and the natural
preservation of varieties and species in a state of nature. For brevity
sake I sometimes speak of natural selection as an intelligent power;--in
the same way as astronomers speak of the attraction of gravity as ruling
the movements of the planets, or as agriculturists speak of man making
domestic races by his power of selection. In the one case, as in the
other, selection does nothing without variability, and this depends in
some manner on the action of the surrounding circumstances on the
organism. I have, also, often personified the word Nature; for I have
found it difficult to avoid this ambiguity; but I mean by nature only the
aggregate action and product of many natural laws,--and by laws only
the ascertained sequence of events.
It has been shown from many facts that the largest amount of life can
be supported on each area, by great diversification or divergence in the
structure and constitution of its inhabitants. We have, also, seen that the
continued production of new forms through natural selection, which
implies that each new variety has some advantage over others,
inevitably leads to the extermination of the older and less improved
forms. These latter are almost necessarily intermediate in structure, as
well as in descent, between the last-produced forms and their original
parent-species. Now, if we suppose a species to produce two or more
varieties, and these in the course of time to produce other varieties, the
principal of good being derived from diversification of structure will
generally lead to the preservation of the most divergent varieties; thus
the lesser differences characteristic of varieties come to be augmented
into the greater differences characteristic of species, and, by the
extermination of the older intermediate forms, new species end by
being distinctly defined objects. Thus, also, we shall see how it is that
organic beings can be classed by what is called a natural method in
distinct groups--species under genera, and genera under families.
As all the inhabitants of each country may be said, owing to their high
rate of reproduction, to be striving to increase in numbers; as each form

comes into competition with many other forms in the struggle for
life,--for destroy any one and its place will be seized by others; as every
part of the organisation occasionally varies in some slight degree, and
as natural selection acts exclusively by the preservation of variations
which are advantageous under the excessively complex conditions to
which each being is exposed, no limit exists to the number, singularity,
and perfection of the contrivances and co-adaptations which may thus
be produced. An animal or a plant may thus slowly become related in
its structure and habits in the most intricate manner to many other
animals and plants, and to the physical conditions of its home.
Variations in the organisation will in some cases be aided by habit, or
by the use and disuse of parts, and they will be governed by the direct
action of the surrounding physical conditions and by correlation of
growth.
On the principles here briefly sketched out, there is no innate or
necessary tendency in each being to its own advancement in the scale
of organisation. We are almost compelled to look at the specialisation
or differentiation of parts or organs for different functions as the best or
even sole standard of advancement; for by such division of labour each
function of body and mind is better performed. And as natural selection
acts exclusively through the preservation of profitable modifications of
structure, and as the conditions of life in each area generally become
more and more complex from the increasing number of different forms
which inhabit it and from most of these forms acquiring a more and
more perfect structure, we may confidently believe, that, on the whole,
organisation advances. Nevertheless a very simple form fitted for very
simple conditions of life might remain for indefinite ages unaltered or
unimproved; for what would it profit an infusorial animalcule, for
instance, or an intestinal worm, to become highly organised? Members
of a high group might even become, and this apparently has often
occurred, fitted for simpler conditions of life; and in this case natural
selection would tend to simplify or degrade the organisation, for