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be shown that before man appeared there was less beauty on the face of
the earth than since he came on the stage. Were the beautiful volute and
cone shells of the Eocene epoch, and the gracefully sculptured ammonites
of the Secondary period, created that man might ages afterward admire
them in his cabinet? Few objects are more beautiful than the minute
siliceous cases of the diatomaceae: were these created that they might be


examined and admired under the higher powers of the microscope? The
beauty in this latter case, and in many others, is apparently wholly due to
symmetry of growth. Flowers rank among the most beautiful productions
of nature; but they have been rendered conspicuous in contrast with the
green leaves, and in consequence at the same time beautiful, so that they
may be easily observed by insects. I have come to this conclusion from find-
ing it an invariable rule that when a flower is fertilized by the wind it never
has a gayly-colored corolla. Several plants habitually produce two kinds of
flowers; one kind open and colored so as to attract insects; the other closed,
not colored, destitute of nectar, and never visited by insects. Hence, we
may conclude that, if insects had not been developed on the face of the
earth, our plants would not have been decked with beautiful flowers, but
would have produced only such poor flowers as we see on our fir, oak, nut,
and ash trees, on grasses, spinach, docks and nettles, which are all fertilized
through the agency of the wind. A similar line of argument holds good
with fruits; that a ripe strawberry or cherry is as pleasing to the eye as to
the palate — that the gayly-colored fruit of the spindlewood tree and the
scarlet berries of the holly are beautiful objects — ^will be admitted by every
one. But this beauty serves merely as a guide to birds and beasts, in order
that the fruit may be devoured and the matured seeds disseminated. I infer
that this is the case from having as yet found no exception to the rule that
seeds are always thus disseminated when embedded within a fruit of any
kind (that is within a fleshy or pulpy envelope), if it be colored of any
brilliant tint, or rendered conspicuous by being white or black.

On the other hand, I willingly admit that a great number of male
animals, as all our most gorgeous birds, some fishes, reptiles, and mammals,
and a host of magnificently colored butterflies, have been rendered beauti-
ful for beauty's sake. But this has been eff"ected through sexual selection,
that is, by the more beautiful males having been continually preferred by
the females, and not for the delight of man. So it is with the music of birds.
We may infer from all this that a nearly similar taste for beautiful colors
and for musical sounds runs through a large part of the animal kingdom.
When the female is as beautifully colored as the male, which is not rarely
the case with birds and butterflies, the cause apparently lies in the colors
acquired through sexual selection having been transmitted to both sexes,
instead of to the males alone. How the sense of beauty in its simplest form —
that is, the reception of a peculiar kind of pleasure from certain colors,
forms, and sounds — ^was first developed in the mind of man and of the
lower animals, is a very obscure subject. The same sort of difficulty is
presented if we inquire how it is that certain flavors and odors give pleasure,
and others displeasure. Habit in all these cases appears to have come to a
certain extent into play; but there must be some fundamental cause in the
constitution of the nervous system in each species.

Natural selection cannot possibly produce any modification in a species
exclusively for the good of another species, though throughout nature


one species incessantly takes advantage of and profits by the structures of
others. But natural selection can and does often produce structures for the
direct injury of other animals, as we see in the fang of the adder, and in the
ovipositor of the ichneumon, by which its eggs are deposited in the living
bodies of other insects. If it could be proved that any part of the structure
of any one species had been formed for the exclusive good of another
species, it would annihilate my theory, for such could not have been pro-
duced through natural selection. Although many statements may be found
in works on natural history to this effect, I cannot find even one which
seems to me of any weight. It is admitted that the rattlesnake has a poison
fang for its own defence and for the destruction of its prey; but some
authors suppose that at the same time it is furnished with a rattle for its
own injury, namely, to warn its prey. I would almost as soon believe that
the cat curls the end of its tail when preparing to spring, in order to warn
the doomed mouse. It is a much more probable view that the rattlesnake
uses its rattle, the cobra expands its frill and the puff-adder swells while
hissing so loudly and harshly, in order to alarm the many birds and beasts
which are known to attack even the most venomous species. Snakes act on
the same principle which makes the hen ruffle her feathers and expand her
wings when a dog approaches her chickens. But I have not space here to
enlarge on the many ways by which animals endeavor to frighten away
their enemies.

Natural selection will never produce in a being any structure more
injurious than beneficial to that being, for natural selection acts solely by
and for the good of each. No organ will be formed, as Paley has remarked,
for the purpose of causing pain or for doing an injury to its possessor. If a
fair balance be struck between the good and evil caused by each part, each
will be found on the whole advantageous. After the lapse of time, under
changing conditions of life, if any part comes to be injurious, it will be
modified; or if it be not so, the being will become extinct as myriads have
become extinct.

Natural selection tends only to make each organic being as perfect as,
or slightly more perfect than, the other inhabitants of the same country
with which it comes into competition. And we see that this is the standard
of perfection attained under nature. The endemic productions of New
Zealand, for instance, are perfect, one compared with another; but they
are now rapidly yielding before the advancing legions of plants and animals
introduced from Europe. Natural selection will not produce absolute per-
fection, nor do we always meet, as far as we can judge, with this high
standard under nature. The correction for the aberration of light is said
by Miiller not to be perfect even in that most perfect organ, the human
eye. Helmholtz, whose judgment no one will dispute, after describing in
the strongest terms the wonderful powers of the human eye, adds these
remarkable words: "That which we have discovered in the way of inexact-
ness and imperfection in the optical machine and in the image on the
retina, is as nothing in comparison with the incongruities which we have


just come across in the domain of the sensations. One might say that nature
has taken deUght in accumulating contradictions in order to remove all
foundation from the theory of a pre-existing harmony between the external
and internal worlds." If our reason leads us to admire with enthusiasm a
multitude of inimitable contrivances in nature, this same reason tells us,
though we may easily err on both sides, that some other contrivances are
less perfect. Can we consider the sting of the bee as perfect, which, when
used against many kinds of enemies, cannot be withdrawn, owing to the
backward serratures, and thus inevitably causes the death of the insect by
tearing out its viscera?

If we look at the sting of the bee, as having existed in a remote progeni-
tor, as a boring and serrated instrument, like that in so many members of
the same great order, and that it has since been modified but not perfected
for its present purpose, with the poison originally adapted for some other
object, such as to produce galls, since intensified, we can perhaps under-
stand how it is that the use of the sting should so often cause the insect's
own death : for if on the whole the power of stinging be useful to the social
community, it will fulfil all the requirements of natural selection, though
it may cause the death of some few members. If we admire the truly won-
derful power of scent by which the males of many insects find their females,
can we admire the production for this single purpose of thousands of
drones, which are utterly useless to the community for any other purpose,
and which are ultimately slaughtered by their industrious and sterile sisters?
It may be difficult, but we ought to admire the savage instinctive hatred
of the queen-bee, which urges her to destroy the young queens, her daugh-
ters, as soon as they are born, or to perish herself in the combat; for un-
doubtedly this is for the good of the community; and maternal love or
maternal hatred, though the latter fortunately is most rare, is all the same
to the inexorable principles of natural selection. If we admire the several
ingenious contrivances by which orchids and many other plants are fertilized
through insect agency, can we consider as equally perfect the elaboration
of dense clouds of pollen by our fir-trees, so that a few granules may be
wafted by chance on to the ovules?

summary: the law of unity of type and of the conditions of
existence embraced by the theory of natural selection

We have in this chapter discussed some of the difficulties and objections
which may be urged against the theory. Many of them are serious; but I
think that in the discussion light has been thrown on several facts, which on
the belief of independent acts of creation are utterly obscure. We have
seen that species at any one period are not indefinitely variable, and are
not Hnked together by a multitude of intermediate gradations, partly be-
cause the process of natural selection is always very slow, and at any one
time acts only on a few forms; and partly because the very process of
natural selection implies the continual supplanting and extinction of pre-


ceding and intermediate gradations. Closely allied species, now living on
a continuous area, must often have been formed when the area was not
continuous, and when the conditions of life did not insensibly graduate
away from one part to another. When two varieties are formed in two
districts of a continuous area, an intermediate variety will often be formed,
fitted for an intermediate zone; but from reasons assigned, the intermediate
variety will usually exist in lesser numbers than the two forms which it
connects; consequently the two latter, during the course of further modifi-
cation, from existing in greater numbers, will have a great advantage over
the less numerous intermediate variety, and will thus generally succeed in
supplanting and exterminating it.

We have seen in this chapter how cautious we should be in concluding
that the most different habits of life could not graduate into each other;
that a bat, for instance, could not have been formed by natural selection
from an animal which at first only glided through the air.

We have seen that a species under new conditions of life may change
its habits; or it may have diversified habits, with some very unlike those
of its nearest congeners. Hence we can understand, bearing in mind that
each organic being is trying to live wherever it can live, how it has arisen
that there are upland geese with webbed feet, ground woodpeckers, diving
thrushes, and petrels with the habits of auks.

Although the belief that an organ so perfect as the eye could have been
formed by natural selection, is enough to stagger any one; yet in the case of
any organ, if we know of a long series of gradations in complexity, each
good for its possessor, then under changing conditions of life, there is no
logical impossibility in the acquirement of any conceivable degree of perfec-
tion through natural selection. In the cases in which we know of no inter-
mediate or transitional states, we should be extremely cautious in conclud-
ing that none can have existed, for the metamorphoses of many organs
show what wonderful changes in function are at least possible. For instance,
a swim-bladder has apparently been converted into an air-breathing lung.
The same organ having performed simultaneously very different functions,
and then having been in part or in whole specialized for one function; and
two distinct organs having performed at the same time the same function,
the one having been perfected while aided by the other, must often have
largely facilitated transitions.

We have seen that in two beings widely remote from each other in the
natural scale, organs serving for the same purpose and in external appear-
ance closely similar may have been separately and independently formed;
but when such organs are closely examined, essential differences in their
structure can almost always be detected; and this naturally follows from
the principle of natural selection. On the other hand, the common rule
throughout nature is infinite diversity of structure for gaining the same end;
and this again naturally follows from the same great principle.

In many cases we are far too ignorant to be enabled to assert that a part
or organ is so unimportant for the welfare of a species, that modifications


in its structure could not have been slowly accumulated by means of natural
selection. In many other cases, modifications are probably the direct result
of the laws of variation or of growth, independently of any good having
been thus gained. But even such structures have often, as we may feel
assured, been subsequently taken advantage of, and still further modified,
for the good of species under new conditions of life. We may, also, believe
that a part formerly of high importance has frequently been retained (as
the tail of an aquatic animal by its terrestrial descendants), though it has
become of such small importance that it could not, in its present state,
have been acquired by means of natural selection.

Natural selection can produce nothing in one species for the exclusive
good or injury of another; though it may well produce parts, organs, and
excretions highly useful or even indispensable, or again highly injurious to
another species, but in all cases at the same time useful to the possessor. In
each well-stocked country natural selection acts through the competition
of the inhabitants, and consequently leads to success in the battle for life,
only in accordance with the standard of that particular country. Hence
the inhabitants of one country, generally the smaller one, often yield to the
inhabitants of another and generally the larger country. For in the larger
country there will have existed more individuals and more diversified forms,
and the competition will have been severer, and thus the standard of per-
fection will have been rendered higher. Natural selection will not necessarily
lead to absolute perfection; nor, as far as we can judge by our limited
faculties, can absolute perfection be everywhere predicated.

On the theory of natural selection we can clearly understand the full
meaning of that old canon in natural history, "Natura non facit saltum."
This canon, if we look to the present inhabitants alone of the world, is not
strictly correct; but if we include all those of past times, whether known
or unknown, it must on this theory be strictly true.

It is generally acknowledged that all organic beings have been formed
on two great laws — Unity of Type, and the Conditions of Existence. By
unity of type is meant that fundamental agreement in structure which we
see in organic beings of the same class, and which is quite independent of
their habits of life. On my theory, unity of type is explained by unity of
descent. The expression of conditions of existence, so often insisted on by
the illustrious Cuvier, is fully embraced by the principle of natural selec-
tion. For natural selection acts by either now adapting the varying parts of
each being to its organic and inorganic conditions of life; or by having
adapted them during past periods of time: the adaptations being aided in
many cases by the increased use or disuse of parts, being affected by the
direct action of the external conditions of life, and subjected in all cases to
the several laws of growth and variation. Hence, in fact, the law of the
Conditions of Existence is the higher law; as it includes, through the in-
heritance of former variations and adaptations, that of Unity of Type.


Miscellaneous Objections to the Theory of Natural Selection

Longevity — Modifications not necessarily Simultaneous — Modifications apparently
of no Direct Service — Progressive Development — Characters of Small Functional
Importance, the most Constant — Supposed Incompetence of Natural Selection
to account for the Incipient Stages of Useful Structures — Causes which interfere
with the Acquisition through Natural Selection of Useful Structures — Grada-
tions of Structure with Changed Functions — Widely Different Organs in Mem-
bers of the Same Class, developed from One and the Same Source — Reasons for
disbelieving in Great and Abrupt Modifications.

I WILL devote this chapter to the consideration of various miscellaneous
objections which have been advanced against my views, as some of the
previous discussions may thus be made clearer; but it would be useless to
discuss all of them, as many have been made by wTiters who have not taken
the trouble to understand the subject. Thus a distinguished German
naturahst has asserted that the weakest part of my theory is, that I consider
all organic beings as imperfect: what I have really said is, that all are not
as perfect as they might have been in relation to their conditions; and this
is showTi to be the case by so many native forms in many quarters of the
world having yielded their places to intruding foreigners. Nor can organic
beings, even if they were at any one time perfectly adapted to their condi-
tions of Life, have remained so, when their conditions changed, unless they
themselves likewise changed; and no one will dispute that the physical
conditions of each country, as well as the number and kinds of its in-
habitants, have undergone many mutations.

A critic has lately insisted, with some parade of mathematical accuracy,
that longevity is a great advantage to all species, so that he who believes
in natural selection "must arrange his genealogical tree" in such a manner
that all the descendants have longer Hves than their progenitors! Cannot
our critics conceive that a biennial plant or one of the lower animals might
range into a cold climate and perish there every winter; and yet, owing to
advantages gained through natural selection, survive from year to year by
means of its seeds or ova? Mr. E. Ray Lankester has recently discussed this
subject, and he concludes, as far as its extreme complexity allows him to
form a judgment, that longevity is generally related to the standard of each
species in the scale of organization, as well as to the amount of expenditure
in reproduction and in general activity. And these conditions have, it is
probable, been largely determined through natural selection.

It has been argued that, as none of the animals and plants of Egypt, of
which we know anything, have changed during the last three or four
thousand years, so probably have none in any part of the world. But, as
Mr. G. H. Lewes has remarked, this line of argument proves too much,
for the ancient domestic races figured on the Egyptian monuments, or
embalmed, are closely similar or even identical with those now living: yet
all naturalists admit that such races have been produced through the modi-



fication of their original types. The many animals which have remained
unchanged since the commencement of the glacial period, would have been
an incomparably stronger case, for these have been exposed to great
changes of climate and have migrated over great distances; whereas, in
Egypt, during the last several thousand years, the conditions of life, as far
as we know, have remained absolutely uniform. The fact of Httle or no
modification having been effected since the glacial period, would have been
of some avail against those who believe in an innate and necessary law of
development, but is powerless against the doctrine of natural selection or
the survival of the fittest, which implies that when variations or individual
differences of a beneficial nature happen to arise, these will be preserved;
but this will be effected only under certain favorable circumstances.

The celebrated palaeontologist, Bronn, at the close of his German transla-
tion of this work, asks how, on the principle of natural selection, can a
variety live side by side with the parent species? If both have become fitted
for slightly different habits of life or conditions, they might Hve together;
and if we lay on one side polymorphic species, in which the variability
seems to be of a peculiar nature, and all mere temporary variations, such
as size, albinism, etc., the more permanent varieties are generally found,
as far as I can discover, inhabiting distinct stations, such as high land or
low land, dry or moist districts. Moreover, in the case of animals which
wander much about and cross freely, their varieties seem to be generally
confined to distinct regions.

Bronn also insists that distinct species never differ from each other in
single characters, but in many parts; and he asks, how it always comes that
many parts of the organization should have been modified at the same time
through variation and natural selection? But there is no necessity for sup-
posing that all the parts of any being have been simultaneously modified.
The most striking modifications, excellently adapted for some purpose,
might, as was formerly remarked, be acquired by successive variations, if
slight, first in one part and then in another; and as they would be trans-
mitted all together, they would appear to us as if they had been simultane-
ously developed. The best answer, however, to the above objection Is
afforded by those domestic races which have been modified, chiefly through
man's power of selection, for some special purpose. Look at the race and
dray horse, or at the greyhound and mastiff. Their w^hole frames, and even
their mental characteristics, have been modified ; but if we could trace each
step in the history of their transformation — and the latter steps can be
traced — we should not see great and simultaneous changes, but first one
part and then another slightly modified and improved. Even when selection
has been applied by man to some one character alone — of which our cul-
tivated plants offer the best instances — it will invariably be found that
although this one part, whether it be the flower, fruit, or leaves, has been
greatly changed, almost all the other parts have been slightly modified.
This may be attributed partly to the principle of correlated growth, and
partly to so-called spontaneous variation.


A much more serious objection has been urged by Bronn, and recently
by Broca, namely, that many characters appear to be of no service what-
ever to their possessors, and therefore cannot have been influenced through
natural selection. Bronn adduces the length of the ears and tails in the
different species of hares and mice — the complex folds of enamel in the
teeth of many animals, and a multitude of analogous cases. With respect
to plants, this subject has been discussed by Nageli in an admirable essay.
He admits that natural selection has effected much, but he insists that the
families of plants differ chiefly from each other in morphological characters,
which appear to be quite unimportant for the welfare of the species. He
consequently believes in an innate tendency toward progressive and more
perfect development. He specifies the arrangement of the cells in the tissues,
and of the leaves on the axis, as cases in which natural selection could not
have acted. To these may be added the numerical divisions in the parts of
the flower, the position of the ovules, the shape of the seed, when not of any
use for dissemination, etc.

There is much force in the above objection. Nevertheless, we ought, in

Online LibraryCharles DarwinThe origin of species → online text (page 19 of 50)