Not only the various domestic races, but the most distinct genera and
orders within the same great class--for instance, mammals, birds,
reptiles, and fishes--are all the descendants of one common
progenitor, and we must admit that the whole vast amount of difference
between these forms has primarily arisen from simple variability. To
consider the subject under this point of view is enough to strike one
dumb with amazement. But our amazement ought to be lessened when we
reflect that beings almost infinite in number, during an almost
infinite lapse of time, have often had their whole organization
rendered in some degree plastic, and that each slight modification of
structure which was in any way beneficial under excessively complex
conditions of life has been preserved, while each which was in any
way injurious has been rigorously destroyed. And the long-continued
accumulation of beneficial variations will infallibly have led to
structures as diversified, as beautifully adapted for various
purposes, and as excellently coordinated as we see in the animals and
plants around us. Hence I have spoken of selection as the paramount
power, whether applied by man to the formation of domestic breeds, or
by nature to the production of species. If an architect were to rear a
noble and commodious edifice without the use of cut stone, by
selecting from the fragments at the base of a precipice wedge-formed
stones for his arches, elongated stones for his lintels, and flat
stones for his roof, we should admire his skill, and regard him as the
paramount power. Now, the fragments of stone, tho indispensable to the
architect, bear to the edifice built by him the same relation which
the fluctuating variations of organic beings bear to the varied and
admirable structures ultimately acquired by their modified
descendants.
[Footnote 17: From "The Origin of Species."]
Some authors have declared that natural selection explains nothing,
unless the precise cause of each slight individual difference be made
clear. If it were explained to a savage utterly ignorant of the art of
building how the edifice had been raised stone upon stone, and why
wedge-formed fragments were used for the arches, flat stones for the
roof, etc.; and if the use of each part and of the whole building were
pointed out, it would be unreasonable if he declared that nothing had
been made clear to him, because the precise cause of the shape of each
fragment could not be told. But this is a nearly parallel case with
the objection that selection explains nothing, because we know not
the cause of each individual difference in the structure of each
being.
The shape of the fragments of stone at the base of our precipice may
be called accidental, but this is not strictly correct; for the shape
of each depends on a long sequence of events, all obeying natural
laws; on the nature of the rock, on the lines of deposition or
cleavage, on the form of the mountain, which depends on its upheaval
and subsequent denudation, and lastly on the storm or earthquake which
throws down the fragments. But in regard to the use to which the
fragments may be put, their shape may be strictly said to be
accidental. And here we are led to face a great difficulty, in
alluding to which I am aware I am traveling beyond my proper province.
An omniscient Creator must have foreseen every consequence which
results from the laws imposed by Him.
But can it reasonably be maintained that the Creator intentionally
ordered, if we use the words in any ordinary sense, that certain
fragments of rock should assume certain shapes so that the builder
might erect his edifice? If the various laws which have determined the
shape of each fragment were not predetermined for the builder's sake,
can it be maintained with any greater probability that He specially
ordained for the sake of the breeder each of the innumerable
variations in our domestic animals and plants; many of these
variations being of no service to man, and not beneficial, far more
often injurious, to the creatures themselves? Did he ordain that the
crop and tail-feathers of the pigeon should vary in order that the
fancier might make his grotesque pouter and fantail breeds? Did He
cause the frame and mental qualities of the dog to vary in order that
a breed might be formed of indomitable ferocity, with jaws fitted to
pin down the bull for man's brutal sport? But if we give up the
principle in one case--if we do not admit that the variations of the
primeval dog were intentionally guided in order that the greyhound,
for instance, that perfect image of symmetry and vigor, might be
formed--no shadow of reason can be assigned for the belief that
variations, alike in nature and the result of the same general laws,
which have been the groundwork through natural selection of the
formation of the most perfectly adapted animals in the world, man
included, were intentionally and specially guided. However much we may
wish it, we can hardly follow Professor Asa Gray in his belief, "that
variation has been led along certain beneficial lines of irrigation."
If we assume that each particular variation was from the beginning of
all time preordained, then that plasticity of organization which leads
to many injurious deviations of structure, as well as the redundant
power of reproduction which inevitably leads to a struggle for
existence, and as a consequence, to the natural selection or survival
of the fittest, must appear to us superfluous laws of nature. On the
other hand, an omnipotent and omniscient Creator ordains everything
and foresees everything. Thus we are brought face to face with a
difficulty as insoluble as is that of free will and predestination.