THE THEORY OF SELECTION (DARWINISM).
Darwinism (Theory of Selection) and Lamarckism (Theory of
Descent).—The Process of Artificial Breeding.—Selection
of the Different Individuals for After-breeding.—The
Active Causes of Transmutation.—Change connected with
Food, and Transmission by Inheritance connected with
Propagation.—Mechanical Nature of these Two
Physiological Functions.—The Process of Natural
Breeding: Selection in the Struggle for
Existence.—Malthus’ Theory of Population.—The
Proportion between the Numbers of Potential and Actual
Individuals of every Species of Organisms.—General
Struggle for Existence, or Competition to attain the
Necessaries of Life.—Transforming Force of the Struggle
for Existence.—Comparison of Natural and Artificial
Breeding.—Selection in the Life of Man.—Military and
Medical Selection.
It is, properly speaking, not quite correctly that the Theory of
Development, with which we are occupied in these pages, is usually
called Darwinism. For, as we have seen from the historical sketch in the
previous chapters, the most important foundation of the Theory of
Development—that is, the Doctrine of Filiation, or Descent—had already
been distinctly enunciated at the beginning of our century, and had been
definitely introduced into science by Lamarck. The portion of the Theory
of Development which maintains the common descent of all species of
animals and plants from the simplest common original forms might,
therefore, in honour of its eminent founder, and with full justice, be
called _Lamarckism_, if the merit of having carried out such a principle
is to be linked to the name of a single distinguished naturalist. On the
other hand, the Theory of Selection, or breeding, might be justly called
_Darwinism_, being that portion of the Theory of Development which shows
us in what way and _why_ the different species of organisms have
developed from those simplest primary forms. (Gen. Morph. ii. 166.)
It is true we find the first trace of an idea of natural selection even
forty years before the appearance of Darwin’s work. For in the year 1818
there was published a paper “On a woman of the white race whose skin
partly resembled that of a negro,” which had been read before the Royal
Society as early as 1813. Its author, Dr. W. C. Wells, states that
negroes and mulattoes are distinguished from the white race by their
immunity from certain tropical diseases. On this occasion he remarks
that all animals have a tendency to change up to a certain degree, and
that farmers, by availing themselves of this tendency, and also by
selection, improve their domestic animals; and then he adds, that what
is done in this latter case “by art, seems to be done with equal
efficiency, though more slowly, by nature, in the formation of varieties
of mankind fitted for the country which they inhabit. Of the accidental
varieties of man which would occur among the first few and scattered
inhabitants of the middle regions of Africa, some one would be better
fitted than the others to bear the diseases of the country. This race
would consequently multiply, while the others would decrease; not only
from their inability to sustain the attacks of disease, but from their
incapacity of contending with their more vigorous neighbours. The
colour of this vigorous race I take for granted, from what has been
already said, would be dark. But the same disposition to form varieties
still existing, a darker and a darker race would in the course of time
occur; and as the darkest would be the best fitted for the climate, this
would at length become the most prevalent, if not the only race, in the
particular country in which it had originated.” He then extends these
same views to the white inhabitants of colder climates. Although Wells
clearly expresses and recognizes the principle of natural selection, yet
it is applied by him only to the very limited problem of the origin of
human races, and not at all to that of the origin of animal and
vegetable species. Darwin’s great merit in having independently
developed the Theory of Selection, and having brought it to complete and
well merited recognition, is as little affected by the earlier and long
forgotten remark of Wells, as by some other fragmentary observations
about natural selection made by Patrick Mathew, and hidden in his book
on “Timber for Shipbuilding, and the Cultivation of Trees,” which
appeared in 1831. The celebrated traveller, Alfred Wallace, who
developed the Theory of Selection independently of Darwin, and had
published it in 1858, simultaneously with Darwin’s first contribution,
likewise stands far behind his greater and elder countryman in regard to
profound conception, as well as to extended application of the theory.
In fact Darwin, by his extremely comprehensive and ingenious development
of the whole doctrine, has acquired a fair claim to see the theory
connected with his own name.
This Theory of Selection, Darwinism in its proper sense, to the
consideration of which we now turn our attention, rests essentially (as
has already been intimated in the last chapter) upon the comparison of
those means which man employs in the breeding of domestic animals and
the cultivation of garden plants, with those processes which in free
nature, outside the cultivated state, lead to the coming into existence
of new species and new genera. We must therefore, in order to understand
the latter processes, first turn to the artificial breeding by man, as
was, in fact, done by Darwin himself. We must inquire into the results
to which man attains by his artificial breeding, and what means are
applied in order to obtain those results; and we must then ask
ourselves, “Are there in nature similar forces and causes acting
similarly to those resorted to by man?”
First, in regard to artificial breeding, we start from the fact last
discussed above, viz., that its products in some cases differ from one
another much more than the productions of natural breeding. It is a fact
that races or varieties often differ from one another in a much greater
degree and in much more important qualities than many so-called species,
or “good species,”—nay, sometimes even more than so-called “good
genera” in their natural state. Compare, for example, the different
kinds of apples which the art of horticulture has derived from one and
the same original apple-form, or compare the different races of horses
which their breeders have derived from one and the same original form of
horse, and it will be easily observed that the differences of the most
different forms are extremely important, and much more important than
the so-called “specific differences,” which are referred to by
zoologists and botanists when comparing wild forms for the purpose of
distinguishing several so-called “good species.”
Now, by what means does man produce this extraordinary difference or
divergence of several forms which are proved to be descended from the
same primary form? In order to answer this question, let us follow a
gardener who desires to produce a new form of a plant, which is
distinguished by the beautiful colour of its flowers. He will first of
all make a selection from a great number of plants which are seedlings
from one and the same parent. He will pick out those plants which
exhibit most distinctly the colour of flower he desires. The colour of
flowers is a very changeable thing. Plants, for example, which as a rule
have a white flower, frequently show deviations into the blue or red.
Now, supposing the gardener wishes to obtain the red colour in a plant
usually producing white flowers, he will very carefully, from among the
many different individuals which are the descendants of one and the same
seed-plant, select those which most distinctly show a reddish tint, and
sow them exclusively, in order to produce new individuals of the same
kind. He would cast aside and no longer cultivate the other seedlings
which show a white or less distinct red colour. He will propagate
exclusively the individual plants whose blossoms show the red most
markedly, and he will sow the seeds produced by these selected plants.
From the seedlings of this second generation, he will again carefully
select those in which the red, which is now visible in the majority of
them, is most distinctly displayed. If such a selection is carried on
during a series of six or ten generations, and if the flower which shows
the deepest red is most carefully selected, the gardener in the sixth or
tenth generation will obtain the desired plants with flowers of a pure
red.
The farmer wishing to breed a special race of animals, for example, a
kind of sheep distinguished by particularly fine wool, proceeds in the
same manner. The only process applied in the improvement of wool
consists in this, that the farmer with the greatest care and
perseverance selects from a whole flock of sheep those individuals which
have the finest wool. These only are used in breeding, and among the
descendants of these selected sheep, those again are chosen which have
the finest wool, etc. If this careful selection is carried on through a
series of generations, the selected breeding-sheep are in the end
distinguished by a wool which differs very strikingly from the wool of
the original parent, and this is exactly the advantage which the breeder
desired.
The differences of the individuals that come into consideration in this
artificial selection are very slight. An ordinary unpractised man is
unable to discover the exceedingly minute differences of individuals
which a practised breeder perceives at the first glance. The business of
a breeder is not easy; it requires an exceedingly sharp eye, great
patience, and an extremely careful manner of treating the organisms to
be bred. In each individual generation, the differences of individuals
are perhaps not seen at all by the uninitiated; but by the accumulation
of these minute differences during a series of generations, the
deviation from the original form becomes in the end very great. It
becomes so great that the artificially produced form may in the end
differ far more from the original form than do two so-called “good
species” in their natural state. The art of breeding has now made such
progress, that man can often at discretion produce certain peculiarities
in cultivated species of animals and plants. To practised gardeners and
farmers, you may give distinct commissions, and say, for example, I wish
to have this species of plant with this or that colour, and with this or
that shape. Where breeding has reached the perfection which it has
attained in England, gardeners and farmers are frequently able to
furnish to order the desired result within a definite period, that is,
at the end of a number of generations. Sir John Sebright, one of the
most experienced English pigeon-breeders, could assert that in three
years he would produce any form of feather, but that he required six
years to obtain any desired form of the head and beak. In the process of
breeding the merino-sheep of Saxony, the animals are three times placed
on a table beside one another, and most carefully compared and studied.
Each time only the best sheep with the finest wool are selected, so that
in the end, out of a great multitude, there remain only some few
animals, but their wool is exquisitely fine, and only these last are
used in breeding. We see, therefore, that the causes through which, in
artificial breeding, great effects are produced, are unusually simple,
and these great effects are obtained simply by accumulating the
differences which in themselves are very insignificant, and become
surprisingly increased by a continually repeated selection.
Before we pass on to a comparison of this artificial with natural
breeding, let us see what natural qualities of the organisms are made
use of by the artificial breeder or cultivator. We can trace all the
different qualities which here come into play to physiological
fundamental qualities of the organism, which are common to all animals
and plants, and are most closely connected with the functions of
_propagation_ and _nutrition_. These two fundamental qualities are
_transmissivity_, or the capability of _transmitting by inheritance_,
and _mutability_, or the capability of _adaptation_. The breeder starts
from the fact that all the individuals of one and the same species are
different, though in a very slight degree, a fact which is as true of
organisms in a wild as in a cultivated state. If you look about you in a
forest consisting of only a single species of tree, for example of
beech, you will certainly not find in the whole forest two trees of this
kind which are absolutely identical or perfectly equal in the form of
their branches, the number of their branches and leaves, blossoms and
fruits. Special differences occur everywhere, just as in the case of
men. There are no two men who are absolutely identical, perfectly equal
in size, in the formation of their faces, the number of their hairs,
their temperament, character, etc. The very same is true of individuals
of all the different species of animals and plants. It is true that in
most organisms the differences are very trifling to the eye of the
uninitiated. Everything here essentially depends on the exercise of the
faculty of discovering these often very minute differences of form. The
shepherd, for example, knows every individual of his flock, solely by
accurately observing their features, while the uninitiated are incapable
of distinguishing at all the different individuals of one and the same
flock. This fact of the individual difference is the extremely important
foundation on which the whole of man’s power of breeding rests. If
individual differences did not exist everywhere, man would not be able
to produce a number of different varieties or races from one and the
same original stock. We must, at the outset, hold fast the principle
that the phenomenon is quite universal; we must necessarily assume it
even where, with the imperfect capabilities of our senses, we are unable
to discover differences. Among the higher plants (the phanerogams, or
flower-plants), where the individual stocks show such numerous
differences in the number of branches or leaves, and in the formation of
the stem and branches, we can almost always easily perceive these
differences. But this is not the case in the lower plants, such as
mosses, algæ, fungi, and in most animals, especially the lower ones. The
distinction of all the individuals of one species is here, for the most
part, extremely difficult or altogether impossible. But there is no
reason for ascribing individual differences only to those organisms in
which we can perceive them at once. We may, on the contrary, with full
certainty assume such individuality as a universal quality of all
organisms, and we can do this all the more surely since we are able to
trace the mutability of individuals to the mechanical conditions of
nutrition. We can show that by influencing nutrition we are able to
produce striking individual differences where they would not exist if
the conditions of nutrition had not been altered. The many complicated
conditions of nutrition are never absolutely identical in two
individuals of a species.
Now, just as we see that the mutability or capability of adaptation has
a causal connection with the general relations of nutrition in animals
and plants, so too we find the second fundamental phenomenon of life,
with which we are here concerned, namely, the capability of
_transmitting by inheritance_, to have a direct connection with the
phenomenon of _propagation_. The second thing that a farmer or gardener
does in artificial breeding, after he has selected, and has consequently
availed himself of the mutability, is to endeavour to hold fast and
develop the modified forms by Inheritance. He starts from the universal
fact that children resemble their parents, that “the apple does not fall
far from the tree.” This phenomenon of Inheritance has hitherto been
scientifically examined only to a very small extent, which may partly
arise from the fact that the phenomenon is of such everyday occurrence.
Every one considers it quite natural that every species should produce
its like; that a horse should not suddenly produce a goose, or a goose a
frog. We are accustomed to look upon these everyday occurrences of
Inheritance as self-evident. But this phenomenon is not so simply
self-evident as it appears at first sight, and in the examination of
Inheritance the fact is very frequently overlooked that the different
descendants, derived from one and the same parents, are in reality
_never_ quite identical, and also never absolutely like the parents, but
are always slightly different. We cannot formulate the principle of
Inheritance, as “Like produces like,” but we must limit the expression
to “Similar things produce similar things.” The gardener, as well as the
farmer, avails himself of the fact of Inheritance in its widest form,
and indeed with special regard to the fact that not only those qualities
of organisms are transmitted by inheritance which they have inherited
from _their_ parents but those also which they themselves have
_acquired_. This is an important point upon which very much depends. An
organism can transmit to its descendants not only those qualities of
form, colour, and size which it has inherited from its parents, but it
can also transmit changes of these qualities, which it has acquired
during its own life through the influence of outward circumstances, such
as climate, nourishment, training, etc.
These are the two fundamental qualities of animals and plants of which
the breeder must avail himself in order to produce new forms. The
theoretical principle of breeding is, indeed, extremely simple, but in
detail the practical application of this simple principle is difficult
and immensely complicated. A thoughtful breeder, acting according to a
definite plan, must understand the art of correctly estimating, in every
case, the general interaction between the two fundamental qualities of
heirship and mutability.
Now, if we examine the real nature of those two important properties of
life, we find that we can trace them, like all physiological functions,
to physical and chemical causes, to the properties and the phenomena of
motion of those substances of which the bodies of animals and plants
consist. As we shall hereafter have to show in the more accurate
consideration of these two functions, the transmission by _Inheritance_,
if we express ourselves quite generally, is essentially dependent upon
the material continuity and partial identity of the matter in the
producing and produced organism, the parents and the child. In every act
of breeding a certain quantity of protoplasm or albuminous matter is
transferred from the parents to the child, and along with it there is
transferred the individually _peculiar molecular motion_. These
molecular phenomena of motion in the protoplasm, which call forth the
phenomena of life, and are their active and true cause, differ more or
less in all living individuals; they are of infinite variety.
_Adaptation_, or transmutation is, on the other hand, essentially the
consequence of material influences, which the substance of the organism
experiences from the material surrounding it,—in the widest sense of
the word from the _conditions_ of life. The external influences of the
latter are communicated to the individual parts of the body by the
molecular processes of nutrition. In every act of Adaptation the
individual molecular motion of the protoplasm, peculiar to each part,
disturbs and modifies the whole individual, or part of it, by
mechanical, physical, or chemical influences. The innate, inherited
vital actions of the protoplasm—that is, the molecular phenomena of
motion of the smallest albuminous particles—are therefore more or less
modified by it. The phenomenon of Adaptation, or transmutation, depends
therefore upon the material influence which the organism experiences
from its surroundings, or its conditions of existence; while the
transmission by Inheritance is due to the partial identity of the
producing and produced organism. These are the real, simple, mechanical
foundations of the artificial process of breeding.
Now Darwin asked himself, Does there exist a similar process of
selection in nature, and are there forces in nature which take the place
of man’s activity in artificial selection? Is there a natural tendency
among wild animals and plants which acts selectingly, in a similar
manner to the artificial selection practised by the designing will of
man? All here depended upon the discovery of such a relation, and Darwin
succeeded in this so satisfactorily, that we consider his theory of
selection completely sufficient to explain, mechanically, the origin of
the wild species of animals and plants. That relation which in free
nature influences the forms of animals and plants, by selecting and
transforming them, is called by Darwin the “_Struggle for Existence_.”
The “Struggle for Existence” has rapidly become a watchword of the day.
Yet this designation is, perhaps, in many respects not very happily
chosen, and the phenomena might probably have been more accurately
described as “_Competition for the Means of Subsistence_.” For under the
name of “Struggle for Life,” many relations are comprehended which
properly and strictly speaking do not belong to it. As we have seen from
the letter inserted in the last chapter, Darwin arrived at the idea of
the “Struggle for Existence” from the study of Malthus’ book “On the
Conditions and the Consequences of the Increase of Population.” It was
proved in that important work, that the number of human beings, on the
average, increases in a geometrical progression, while the amount of
articles of food increase only in an arithmetical progression. This
disproportion gives rise to a number of inconveniences in the human
community, which cause among men a continual competition to obtain the
necessary means of life, which do not suffice for all.
Darwin’s theory of the struggle for life is, to a certain extent, a
general application of Malthus’ theory of population to the whole of
organic nature. It starts from the consideration that the number of
_possible_ organic individuals which might arise from the germs
produced, is far greater than the number of _actual_ individuals which,
in fact, do simultaneously live on the earth’s surface. The number of
possible or _potential individuals_ is given us by the number of the
eggs and organic germs produced by organisms. The number of these germs,
from each of which, under favourable circumstances, an individual might
arise, is very much larger than the number of real or actual
_individuals_—that is, of those that really arise from these germs,
come into life, and propagate themselves. By far the greater number of
germs perish in the earliest stage of life, and it is only some favoured
organisms which manage to develop, and actually survive the first period
of early youth, and finally succeed in propagating themselves. This
important fact is easily proved by a comparison of the number of eggs in
a given species with the number of individuals which exist of this
species. These numerical relations show the most striking contrast.
There are, for example, species of fowls which lay great numbers of
eggs, and yet are among the rarest of birds; and the bird which is said
to be the commonest (the most widely spread) of all, the stormy petrel
(_Procellaria glacialis_), lays only a single egg. The relation is the
same in other animals. There are many very rare invertebrate animals,
which lay immense quantities of eggs; and others again which produce
only very few eggs, and yet are among the commonest of animals. Take,
for example, the proportion which is observed among the human
tape-worms. Each tape-worm produces within a short period millions of
eggs, while man, in whom these tape-worms are lodged, forms a far
smaller number of eggs, and yet fortunately there are fewer tape-worms
than human beings. In like manner, among plants there are many splendid
orchids, which produce thousands of seeds and yet are very rare, and
some kinds of asters (Compositæ), which have but few seeds, are
exceedingly common.
This important fact might be illustrated by an immense number of
examples. It is evidently, therefore, not the number of actually
existing germs which indicates the number of individuals which
afterwards come into life and maintain themselves in life; but rather
the case is this, that the number of adult individuals is limited by
other circumstances, especially by the relations in which the organism
stands to its organic and inorganic surroundings. Every organism, from
the commencement of its existence, struggles with a number of hostile
influences: it struggles against animals which feed on it, and to which
it is the natural food, against animals of prey and parasites; it
struggles against inorganic influences of the most varied kinds, against
temperature, weather, and other circumstances; but it also struggles
(and this is much the most important!), above all, against organisms
most like and akin to itself. Every individual, of every animal and
vegetable species, is engaged in the fiercest competition with every
other individual of the same species which lives in the same place with
it. In the economy of nature the means of subsistence are nowhere
scattered in abundance, but are very limited, and far from sufficient
for the number of organisms which might develop from the germs produced.
Therefore the young individuals of most species of animals and
vegetables must have hard work in obtaining the means of subsistence;
this necessarily causes a competition among them in order to obtain the
indispensable supplies of life.
This great competition for the necessaries of life goes on everywhere
and at all times, among human beings and animals as well as among
plants; in the case of the latter this circumstance, at first sight, is
not so clearly apparent. If we examine a field which is richly sown with
wheat, we can see that of the numerous young plants (perhaps some
thousands) which shoot up on a limited space, only a very small
proportion preserve themselves in life. A competition takes place for
the space of ground which each plant requires for fixing its root, a
competition for sunlight and moisture. And in the same manner we find
that, among all animal species, all the individuals of one and the same
species compete with one another to obtain these indispensable means of
life, or the conditions of existence in the wide sense of the word. They
are equally indispensable to all, but really fall to the lot of only a
few—“Many are called, but few are chosen.” The fact of the great
competition is quite universal. You need only to cast a glance at human
society, where this competition exists everywhere, and in all the
different branches of human activity. Here, too, a struggle is brought
about by the free competition of the different labourers of one and the
same class. Here too, as everywhere, this competition benefits the
thing, or the work, which is the object of competition. The greater and
more general the competition, the more quickly improvements and
inventions are made in the branch of labour, and the higher is the grade
of perfection of the labourers themselves.
The position of the different individuals in this struggle for life is
evidently very unequal. Starting from the inequality of individuals,
which is a recognized fact, we must in all cases necessarily suppose
that all the individuals of one and the same species do not have equally
favourable prospects. Even at the beginning they are differently placed
in this competition by their different strengths and abilities,
independently of the fact that the conditions of existence are
different, and act differently at every point of the earth’s surface. We
evidently have an infinite combination of influences, which, together
with the original inequality of the individuals during the competition
for the conditions of existence, favour some individuals and prejudice
others. The favoured individuals will gain the victory over the others,
and while the latter perish more or less early, without leaving any
descendants, the former alone will be able to survive and finally to
propagate the species. As, therefore, it is clear that in the struggle
for life the favoured individuals succeed in propagating themselves, we
shall (even as the result of this relation) perceive in the next
generation differences from the preceding one. Some individuals of this
second generation, though perhaps not all of them, will, by inheritance,
receive the individual advantage by which their parents gained the
victory over their rivals.
But now—and this is a very important law of inheritance—if such a
transmission of a favourable character is continued through a series of
generations, it is not simply transmitted in the original manner, but it
is constantly increased and strengthened, and in a last generation it
attains a strength which distinguishes this generation very essentially
from the original parent. Let us, for example, examine a number of
plants of one and the same species which grow together in a very dry
soil. As the hairs on the leaves of plants are very useful for receiving
moisture from the air, and as the hairs on the leaves are very
changeable, the individuals possessing the thickest hair on their leaves
will have an advantage in this unfavourable locality where the plants
have directly to struggle with the want of water, and in addition to
this have to compete with one another for the possession of what little
water there may be. These alone hold out, while the others possessing
less hairy leaves perish; the more hairy ones will be propagated, and
their descendants will, on the average, be more distinguished by their
thick and strong hairs than the individuals of the first generation. If
this process is continued for several generations in one and the same
locality, there will arise at last such an increase of this
characteristic, such an increase of the hairs on the surface of the
leaf, that an entirely new species seems to present itself. It must here
be observed, that in consequence of the interactions of all the parts of
every organism, generally one individual part cannot be changed without
at the same time producing changes in other parts. If, for instance, in
our imaginary example, the number of the hairs on the leaves is greatly
increased, a certain amount of nourishment is thereby withdrawn from
other parts; the material which might be employed to form flowers or
seeds is diminished, and a smaller size of the flower or seed will then
be the direct or indirect consequence of the struggle for life, which in
the first place only produced a change in the leaves. Thus the struggle
for life, in this instance, acts as a means of selecting and
transforming. The struggle of the different individuals to obtain the
necessary conditions of existence, or, taking it in its widest sense,
the inter-relations of organisms to the whole of their surroundings,
produce mutations of form such as are produced in the cultivated state
by the action of man’s selection.
This agency will perhaps appear at first sight small and insignificant,
and the reader will not be inclined to concede to the action of such
relations the weight which it in reality possesses. I must therefore
find space in a subsequent chapter to put forward further examples of
the immense and far-reaching power of transformation exhibited in
natural selection. For the present I will confine myself to simply
placing side by side the two processes of artificial and natural
selection, and clearly explaining the agreement and the differences of
the two.
Both natural and artificial selection are quite simple natural,
mechanical relations of life, which depend upon the _interaction_ of two
physiological functions, namely, on _Adaptation_ and _Inheritance_,
functions which, as such, must again be traced to physical and chemical
properties of organic matter. The difference between the two forms of
selection consists in this: in artificial selection the will of man
makes the selection according to a _plan_, whereas in natural selection,
the struggle for life (that universal inter-relation of organisms) acts
_without a plan_, but otherwise produces quite the same result, namely,
a selection of a particular kind of individuals for propagation. The
alterations produced by artificial selection are turned to the advantage
of _those who make the selection_; in natural selection, on the other
hand, to the advantage of the _selected organism_.
These are the most essential differences and agreements of the two modes
of selection; it must, however, be further observed that there is
another difference, viz., in the duration of time required for the two
processes of selection. Man in his artificial selection can produce very
important changes in a very short time, while in natural selection
similar results are obtained only after a much longer time. This arises
from the fact that man can make his selection with much greater care.
Man is able with the greatest nicety to pick out individuals from a
large number, drop the others, and to employ only the privileged beings
for propagation, which is not the case in natural selection. In natural
conditions, besides the privileged individuals which first succeed in
propagating themselves, some few or many of the less distinguished
individuals will propagate themselves by the side of the former.
Moreover, man can prevent the crossing of the original and the new form,
which in natural selection is often unavoidable. If such a crossing,
that is, a sexual connection, of the new variety with the original forms
takes place, the offspring thereby produced generally returns to the
original character. In natural selection, such a crossing can be avoided
only when the new variety by migration separates from the original and
isolates itself.
Natural selection therefore acts much more slowly; it requires much
longer periods than the artificial process of selection. But it is an
essential consequence of this difference, that the product of artificial
selection disappears much more easily, and that the new form returns
rapidly to the earlier one, which is not the case in natural selection.
The new species arising from natural selection maintain themselves much
more permanently, and return much less easily to the original form, than
is the case with products of artificial selection, and accordingly
maintain themselves during a much longer time than the artificial races
produced by man. But these are only subordinate differences, which are
explained by the different conditions of natural and artificial
selection, and in reality are connected only with differences in the
duration of time. The nature of the transformation and the means by
which it is produced are entirely the same in both artificial and
natural selection. (Gen. Morph. ii. 248.)
The thoughtless and narrow-minded opponents of Darwin are never tired of
asserting that his theory of selection is a groundless conjecture, or at
least an hypothesis which has yet to be proved. That this assertion is
completely unfounded, may be perceived even from the outlines of the
doctrine of selection which have just been discussed. Darwin assumes no
kind of unknown forces of nature, nor hypothetical conditions, as the
acting causes for the transformation of organic forms, but solely and
simply the universally recognized vital activities of all organisms,
which we term _Inheritance_ and _Adaptation_. Every naturalist
acquainted with physiology knows that these two phenomena are directly
connected with the functions of propagation and nutrition, and, like all
other phenomena of life, are purely mechanical processes of nature, that
is, they depend upon the molecular phenomena of motion in organic
matter. That the interaction of these two functions effect a continual,
slow transmutation of organic forms, is a necessary result of the
struggle for existence. But this, again, is no more a hypothetical
relation, nor one requiring a proof, than is the interaction of
Inheritance and Adaptation. The struggle for life is a mathematical
necessity, arising from the disproportion between the limited number of
places in nature’s household, and the excessive number of organic germs.
The origin of new species is moreover greatly favoured by the active or
passive _migrations_ of animals and plants, which takes place everywhere
and at all times, without being, however, entitled to rank as
_necessary_ agents in the process of natural selection.
The origin of new species by natural selection, or, what is the same
thing, by the interaction of Inheritance and Adaptation in the struggle
for life, is therefore a _mathematical necessity_ of nature which needs
no further proof. Whoever, in spite of the present state of our
knowledge, still seeks for _proofs_ for the Theory of Selection, only
shows that he either does not thoroughly understand the theory, or is
not sufficiently acquainted with the biological facts—has not the
requisite amount of experimental knowledge in Anthropology, Zoology, and
Botany.
If, as we maintain, natural selection is the great active cause which
has produced the whole wonderful variety of organic life on the earth,
all the interesting phenomena of _human life_ must also be explicable
from the same cause. For man is after all only a most highly-developed
vertebrate animal, and all aspects of human life have their parallels,
or, more correctly, their lower stages of development in the animal
kingdom. The whole history of nations, or what is called “Universal
History,” must therefore be explicable by means of “natural
selection,”—must be a physico-chemical process, depending upon the
interaction of Adaptation and Inheritance in the struggle for life. And
this is actually the case. We shall give further proofs of this later
on.
It appears of interest here to remark that not only _natural_ selection,
but also _artificial_ selection exercises its influence in many ways in
universal history. A remarkable instance of _artificial selection in
man_, on a great scale, is furnished by the ancient Spartans, among
whom, in obedience to a special law, all newly-born children were
subject to a careful examination and selection. All those that were
weak, sickly, or affected with any bodily infirmity, were killed. Only
the perfectly healthy and strong children were allowed to live, and they
alone afterwards propagated the race. By this means, the Spartan race
was not only continually preserved in excellent strength and vigour, but
the perfection of their bodies increased with every generation. No doubt
the Spartans owed their rare degree of masculine strength and rough
heroic valour (for which they are eminent in ancient history) in a
great measure to this artificial selection.
Many tribes also among the Red Indians of North America (who at present
are succumbing in the struggle for life to the superior numbers of the
white intruders, in spite of a most heroic and courageous resistance)
owe their rare degree of bodily strength and warlike bravery to a
similar careful selection of the newly-born children. Among them, also,
all children that are weak or affected with any infirmity are
immediately killed, and only the perfectly strong individuals remain in
life, and propagate the race. That the race becomes greatly
strengthened, in the course of very many generations, by this artificial
selection cannot in itself be doubted, and is sufficiently proved by
many well known facts.
The opposite of this artificial selection of the wild Redskins and the
ancient Spartans is seen in the individual selection which is
universally practised in our modern military states, for the purpose of
maintaining standing armies, and which, under the name of _military
selection_, we may conveniently consider as a special form of selection.
Unfortunately, in our day, militarism is more than ever prominent in our
so-called “civilization”; all the strength and all the wealth of
flourishing civilized states are squandered on its development; whereas
the education of the young, and public instruction, which are the
foundations of the true welfare of nations and the ennobling of
humanity, are neglected and mismanaged in a most pitiable manner. And
this is done in states which believe themselves to be the privileged
leaders of the highest human intelligence, and to stand at the head of
civilization. As is well known, in order to increase the standing army
as much as possible, all healthy and strong young men are annually
selected by a strict system of recruiting. The stronger, healthier, and
more spirited a youth is, the greater is his prospect of being killed by
needle-guns, cannons, and other similar instruments of civilization. All
youths that are unhealthy, weak, or affected with infirmities, on the
other hand, are spared by the “military selection,” and remain at home
during the war, marry, and propagate themselves. The more useless, the
weaker, or infirmer the youth is, the greater is his prospect of
escaping the recruiting officer, and of founding a family. While the
healthy flower of youth dies on the battle-field, the feeble remainder
enjoy the satisfaction of reproduction and of transmitting all their
weaknesses and infirmities to their descendants. According to the laws
of transmission by inheritance, there must necessarily follow in each
succeeding generation, not only a further extension, but also a more
deeply-seated development of weakness of body, and what is inseparable
from it, a condition of mental weakness also. This and other forms of
artificial selection practised in our civilized states sufficiently
explain the sad fact that, in reality, weakness of the body and weakness
of character are on the perpetual increase among civilized nations, and
that, together with strong, healthy bodies, free and independent spirits
are becoming more and more scarce.
To the increasing enervation of modern civilized nations, which is the
necessary consequence of military selection, there is further added
another evil. The progress of modern medical science, although still
little able really to cure diseases, yet possesses and practises more
than it used to do the art of prolonging life during lingering, chronic
diseases for many years. Such ravaging evils as consumption, scrofula,
syphilis, and also many forms of mental disorders, are transmitted by
inheritance to a great extent, and transferred by sickly parents to some
of their children, or even to the whole of their descendants. Now, the
longer the diseased parents, with medical assistance, can drag on their
sickly existence, the more numerous are the descendants who will inherit
incurable evils, and the greater will be the number of individuals,
again, in the succeeding generation, thanks to that artificial “_medical
selection_,” who will be infected by their parents with lingering,
hereditary disease.
If any one were to venture the proposal, after the examples of the
Spartans and Redskins, to kill, immediately upon their birth, all
miserable, crippled children to whom with certainty a sickly life could
be prophesied, instead of keeping them in life injurious to them and to
the race, our so-called “humane civilization” would utter a cry of
indignation. But the same “humane civilization” thinks it quite as it
should be, and accepts without a murmur, that at the outbreak of every
war (and in the present state of civilized life, and in the continual
development of standing armies, wars must naturally become more
frequent) hundreds and thousands of the finest men, full of youthful
vigour, are sacrificed in the hazardous game of battles. The same
“humane civilization” at present praises the abolition of capital
punishment as a “liberal measure!” And yet capital punishment for
incorrigible and degraded criminals is not only just, but also a benefit
to the better portion of mankind; the same benefit is done by destroying
luxuriant weeds, for the prosperity of a well cultivated garden. As by
a careful rooting out of weeds, light, air, and ground is gained for
good and useful plants, in like manner, by the indiscriminate
destruction of all incorrigible criminals, not only would the struggle
for life among the better portion of mankind be made easier, but also an
advantageous artificial process of selection would be set in practice,
since the possibility of transmitting their injurious qualities by
inheritance would be taken from those degenerate outcasts.
Against the injurious influence of artificial military and medical
selection, we fortunately have a salutary counterpoise, in the
invincible and much more powerful influence of _natural selection_,
which prevails everywhere. For in the life of man, as well as in that of
animals and plants, this influence is the most important transforming
principle, and the strongest lever for progress and amelioration. The
result of the struggle for life is that, in the long run, that which is
better, because more perfect, conquers that which is weaker and
imperfect. In human life, however, this struggle for life will ever
become more and more of an intellectual struggle, not a struggle with
weapons of murder. The organ which, above all others, in man becomes
more perfect by the ennobling influence of natural selection, is the
_brain_. The man with the most perfect understanding, not the man with
the best revolver, will in the long run be victorious; he will transmit
to his descendants the qualities of the brain which assisted him in the
victory. Thus then we may justly hope, in spite of all the efforts of
retrograde forces, that the progress of mankind towards freedom, and
thus to the utmost perfection, will, by the happy influence of natural
selection, become more and more certain.