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IN a well-known passage towards the close of the “ Origin of I Species,” Mr. Darwin supposes the question to be put to him, How far does your doctrine extend, and what amount of ground does it cover ? The answer is perfectly frank and clear. Practically it covers the whole area of life. Every class, at least of animals and plants, must own a common ancestor, and probably these class-founders are themselves only brethren descended from some yet remoter stock. Of the former of these two positions he speaks confidently. “I cannot doubt,” he says, “ that the theory of descent, with modification, embraces all the members of the same class. I believe that animals have descended from at most only four or five progenitors, and plants from an equal or lesser number.” Of the latter he speaks with more reserve. “ Analogy would lead me one step further, namely, to the belief that all animals and plants have descended from some one prototype. But analogy," he adds, “may be a deceitful guide. Nevertheless he sees sufficient reason to justify him in following its guidance in this instance, and finally sums up his opinion in the following remarkable words : “ Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed.”

The natural inference from these words would be that Mr. Darwin considered his theory of natural selection as sufficient to account for all the varieties of life on the face of the earth. But it is not a necessary inference. For he is speaking, in this passage, not precisely of the doctrine of natural selection, but of the doctrine of " descent with modification ;” and the two ideas are perfectly distinct. For it is quite possible that all living beings may be descended from a single primordial form, and yet that natural selection may not be the only

agency employed in the determination of their actual variety. Other methods and other forces may have conspired with it, checked or thwarted it, in the work of educing from one common form the boundless multiformity which now meets our eyes. No doubt the whole course of Mr. Darwin's reasonings and illustrations leads us to the conviction that in his judgment the unassisted action of natural selection is sufficient to produce all the necessary modifications, but so far as express words go, he has not excluded—at any rate in the passage which I have quoted—the possibility of the co-operation or interference of some other cause; and it is important to call attention to this, because a very high authority on this subject, Mr. A. R. Wallace—the independent originator, and the most able defender of the theory which bears Mr. Darwin's name has recently proclaimed his conviction that natural selection by itself is inadequate to the production of at least one, and that the most important, form of life. In other words it is impossible, in Mr. Wallace's opinion, that man can have been developed from the inferior animals by the process of natural selection alone. Whatever else it may have done, it is unequal to this, the great and crowning act of creative power. *

To understand his reasonings we must first get a clear idea of what the doctrine of natural selection is. It does not imply, as many will persist in assuming, any capacity in the individual to alter his own structure, and adapt himself to surrounding circumstances. The individual does not materially change. Such as he is born, such, in his physical structure, he will remain to the end of his life. Only if his physical structure does not happen to be well adapted to the circumstances in which he finds himself, his life will be a short one. His neighbour, who happens, by some small variation, to be slightly better adapted to those circumstances, will live longer. And, moreover, since the offspring inherit the parents' peculiarities, the descendants of this latter are likely to prevail to the exclusion of those of the former; and thus, in the course of some generations, the prevailing type and character of the whole family will be slightly modified. It is not the individual, but the collection of similar individuals, or the Kind—a word which may be usefully employed to avoid the technical meaning attaching to class or species—that changes. And it changes only by means of changing its units, by dropping out from time to time those that are unsuitable, and keeping in and preserving those that are suitable. In this way it adapts itself

• See “ Contributions to the Theory of Natural Selection.(Macmillan & Co.) By A. R. Wallace. This paper is little more than an expansion of part of the argument in one of these Essays.

to the perpetual changes of surrounding circumstances, and keeps itself by its own variations in constant harmony with the ever-varying world around it. As earth and seas, forest, river and meadow, climate and temperature, are never for a moment stationary, but maintain a perpetual ebb and flow of ceaseless interchange, so the general forms and types of life, which are affected by all these influences, are also in continual and corresponding flux. Both are always in a condition of instability in themselves, because both are always in perfect harmony with each other. But it follows from this that no modification can possibly be introduced into any form or type of life, unless it be beneficial to the creature modified-unless it tend, in some way or other, to bring him more into harmony with the conditions around him than he was before. If the change be merely a matter of indifference, doing neither good nor harm to the possessor, it will make no impression on the Kind. It is an individual peculiarity which may re-appear again here and there in other individuals, but which has no tendency to prevail over other similar peculiarities in others. But if the change is actually injurious, it will vanish at once. The unlucky possessor of it will be inferior to his neighbours in the struggle for existence ; his life will be cut short sooner than that of others; his offspring, if they inherit his peculiarity, will inherit also his disadvantages, and will soon perish out of the Kind, leaving no trace behind them. Natural selection is like fortune; it favours only the brave; it helps those only who can help themselves; it rejects the weak, the puny, the illprovided, and ill-adapted; and its effect is best described as the survival of the fittest.

Now let us apply these principles to the case of man. Were the changes by which the Kind passed-if it did pass—from some lower type to the human type such as would be manifestly beneficial in the first instance to the individuals who were affected by these changes ? Because, if they were not, that transition could never have been effected by natural selection. If it occurred at all, some other agency must be taken into account. What, then, were these changes? We cannot, of course, tell exactly, unless we knew—as we certainly do not know—the form of life which immediately preceded the human. But let us assume for the moment that the anthropoid apes and man are the extremities of divergent lines from some remote ancestor, uniting in himself the characteristics which they have in common; how would the differentiation begin to be carried on ? One of the most marked peculiarities in man is the soft, smooth skin. Alone among the mammalia, he is unprotected either by the hardness or the shagginess of his integument. He bas neither the impenetrable armour of the rhinoceros, nor the

thick fur of the bear, nor the warm wool of the sheep. Was it any advantage to the first individual that came into the world with this soft, smooth skin, or with any approximation to it, beyond his fellows? Was it a peculiarity likely to help him in the struggle for life—to enable him to survive when others perished ?—likely, therefore, when transmitted to his offspring, to appear in greater force in the next generation; and gradually, by its superior adaptation to surrounding circumstances, to supplant the tough or hairy skins which had preceded and accompanied it? Was it likely, in short, to become an object of natural selection ? Is it not, on the contrary, quite plain that the very reverse would be the case ? The accidental possessor of this smooth skin would clearly be at a great disadvantage. He would succumb beneath the attacks of enemies which his hardier fellows could successfully resist. Rain and frost and cold would work their bitter will upon him unchecked. Inclement seasons, which only produced a moderate inconvenience, or none at all, to creatures with thick or shaggy hides, would soon prove fatal to the animal we are imagining. There is no conceivable reason why such an animal should live and perpetuate his peculiarity, while others which did not possess it perished; there is, on the contrary, every reason to suppose that such an animal, born for the first time, an anomaly in a shaggy world, would speedily be eliminated and leave no trace behind him. That is to say, it is impossible to picture a condition of things in which a kind of creatures distinguished by smooth skins could have arisen by the process of natural selection. In other words, natural selection cannot account for the origin of this peculiarity in the human form.

But that is not all. The theory of natural selection not only requires that every change promoted by it should be for the benefit of the possessor; it requires also that it should be for his direct and immediate benefit; that it should be no greater than is necessary to give him some instant advantage, however slight, over his fellows. For it does not act, any more than Nature herself, per saltum. It rests for its motive force upon the variation which always exists between a parent and an offspring; and this variation is, for the most part, very slight. It is enough to distinguish one from the other, but never much more. It is generally so small that the unpractised eye often fails to see any difference whatever. We do not mistake our friends for their fathers, though, if we do not know them well, we are liable sometimes to get confused between brothers and sisters; but, except to the shepherd, a flock of sheep seem to be all exactly alike. The differences between individuals of the same kind are for the most part very small, and it is only


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on these differences that natural selection acts. Hence it happens that the transformation of one kind into another is a very slow and gradual process, because it has to be accomplished by a series of very small steps. A long step cannot be taken unless it is more to the advantage of the individual than a short step in the same direction, because it is certain that many more individuals will be born in any given generation with the small than with the large variation; and, unless the large one has some direct advantage over the small, the mere superiority of numbers will give the victory to the latter. Let us illustrate this by an example. Suppose a flower, such as the Angræcum Sesquipedale of Madagascar, with a very deep nectary, and a supply of nectar at the bottom of it. This can only be reached by a moth with a very long proboscis. Suppose also that this nectary has, from any cause, a continual tendency to lengthen in successive generations. It is evident that moths that happen to be born with probosces longer than the average will have an advantage over those that are born with them shorter. They will have at least, other things being equal, one more flower to feed on, and so have a better chance for life. Natural selection will therefore operate to produce a Kind of moths with long probosces. But it will not give any preference to a proboscis longer than is required for that special purpose. A proboscis which has an inch to spare would not be a bit more useful than one which could just drain the nectar and no more. And while many moths would be born with the slight additional length necessary for this, few or none would be born with the proboscis an inch longer. Such moths would be monstrosities, and monstrosities are always rare. And there would be no cause at all tending to perpetuate such a monstrosity and to counteract the universal tendency in all such cases to return, if unchecked, to the normal type--a tendency which is, in point of fact, simply another expression of the perpetual effort, which all life manifests, to bring itself into absolute harmony with all around it. The music of the spheres will not tolerate a discord; if a half-note too high or too low can be caught occasionally by the listening ear, it is soon swept out and lost in the full strong current of advancing sound. The office of natural selection is to maintain this concord, and it does it by favouring those slight variations which, by bringing their possessor more into harmony with the world around, give him an instant advantage over his fellows. It does not favour any larger variations; it has no forecasting eye to the possibilities of any future advantage to be derived from them.

Now let us apply this principle once more to the case of man, and in so doing let us pass from an external and super

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