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.