Charles Darwin On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (6th Edition, 1892)

from Chapter IV: Natural Selection; or the Survival of the Fittest

ow will the struggle for existence, are born than can possibly survive) that briefly discussed in the last chapter, individuals having any advantage, however H act in regard to variation? Can the slight, over others, would have the best principle of selection, which we have seen is chance of surviving and procreating their so potent in the hands of man, apply under kind? On the other hand, we may feel sure nature? I think we shall see that it can act that any variation in the least degree most efficiently. Let the endless number of injurious would be rigidly destroyed. This slight variations and individual differences preservation of favourable individual occurring in our domestic productions, and, differences and variations, and the in a lesser degree, in those under nature, be destruction of those which are injurious, I borne in mind; as well as the strength of the have called Natural Selection, or the hereditary tendency. Under domestication, it Survival of the Fittest. Variations neither may truly be said that the whole useful nor injurious would not be affected organisation becomes in some degree by natural selection, and would be left either plastic. But the variability, which we almost a fluctuating element, as perhaps we see in universally meet with in our domestic certain polymorphic species, or would productions is not directly produced, as ultimately become fixed, owing to the nature Hooker and Asa Gray have well remarked, of the organism and the nature of the by man; he can neither originate varieties conditions.1 nor prevent their occurrence; he can only preserve and accumulate such as do occur. Several writers have Unintentionally he exposes organic beings misapprehended or objected to the term to new and changing conditions of life, and Natural Selection. Some have even imagined variability ensues; but similar changes of that natural selection induces variability, conditions might and do occur under nature. whereas it implies only the preservation of Let it also be borne in mind how infinitely such variations as arise and are beneficial to complex and close-fitting are the mutual the being under its conditions of life. No one relations of all organic beings to each other objects to agriculturists speaking of the and to their physical conditions of life; and potent effects of man’s selection; and in this consequently what infinitely varied case the individual differences given by diversities of structure might be of use to nature, which man for some object selects, each being under changing conditions of must of necessity first occur. Others have life. Can it then be thought improbable, seeing that variations useful to man have 1 Compare the text of the first edition (1859): “This undoubtedly occurred, that other variations preservation of favourable variations and the useful in some way to each being in the rejection of injurious variations, I call Natural great and complex battle of life, should Selection. Variations neither useful nor injurious occur in the course of many successive would not be affected by natural selection, and would be left a fluctuating element, as perhaps we see in the generations? If such do occur, can we doubt species called polymorphic.” In the first edition, the (remembering that many more individuals title of this chapter was simply “Natural Selection.”

1 objected that the term selection implies powerful the influence of a single introduced conscious choice in the animals which tree or mammal has been shown to be. But become modified; and it has even been in the case of an island, or of a country urged that, as plants have no volition, partly surrounded by barriers, into which natural selection is not applicable to them! new and better adapted forms could not In the literal sense of the word, no doubt, freely enter, we should then have places in natural selection is a false term; but who the economy of nature which would ever objected to chemists speaking of the assuredly be better filled up if some of the elective affinities of the various elements?— original inhabitants were in some manner and yet an acid cannot strictly be said to modified; for, had the area been open to elect the base with which it in preference immigration, these same places would have combines. It has been said that I speak of been seized on by intruders. In such cases, natural selection as an active power or slight modifications, which in any way Deity; but who objects to an author speaking favoured the individuals of any species, by of the attraction of gravity as ruling the better adapting them to their altered movements of the planets? Every one knows conditions, would tend to be preserved; and what is meant and is implied by such natural selection would have free scope for metaphorical expressions; and they are the work of improvement. almost necessary for brevity. So again it is difficult to avoid personifying the word We have good reason to believe, as Nature; but I mean by nature, only the shown in the first chapter, that changes in aggregate action and product of many the conditions of life give a tendency to natural laws, and by laws the sequence of increased variability; and in the foregoing events as ascertained by us. With a little cases the conditions the changed, and this familiarity such superficial objections will would manifestly be favourable to natural be forgotten. selection, by affording a better chance of the occurrence of profitable variations. Unless We shall best understand the such occur, natural selection can do nothing. probable course of natural selection by Under the term of “variations,” it must never taking the case of a country undergoing be forgotten that mere individual differences some slight physical change, for instance, of are included. As man can produce a great climate. The proportional numbers of its result with his domestic animals and plants inhabitants will almost immediately undergo by adding up in any given direction a change, and some species will probably individual differences, so could natural become extinct. We may conclude, from selection, but far more easily from having what we have seen of the intimate and incomparably longer time for action. Nor do complex manner in which the inhabitants of I believe that any great physical change, as each country are bound together, that any of climate, or any unusual degree of change in the numerical proportions of the isolation, to check immigration, is necessary inhabitants, independently of the change of in order that new and unoccupied places climate itself, would seriously affect the should be left for natural selection to fill up others. If the country were open on its by improving some of the varying borders, new forms would certainly inhabitants. For as all the inhabitants of each immigrate, and this would likewise seriously country are struggling together with nicely disturb the relations of some of the former balanced forces, extremely slight inhabitants. Let it be remembered how modifications in the structure or habits of

2 one species would often give it an advantage short wool to the same climate; does not over others; and still further modifications of allow the most vigorous males to struggle the same kind would often still further for the females; he does not rigidly destroy increase the advantage, as long as the all inferior animals, but protects during each species continued under the same conditions varying season, as far as lies in his power, of life and profited by similar means of all his productions. He often begins his subsistence and defence. No country can be selection by some half-monstrous form, or at named in which all the native inhabitants are least by some modification prominent now so perfectly adapted to each other and enough to catch the eye or to be plainly to the physical conditions under which they useful to him. Under nature, the slightest live, that none of them could be still better differences of structure or constitution may adapted or improved; for in all countries, the well turn the nicely-balanced scale in the natives have been so far conquered by struggle for life, and so be preserved. How naturalised productions that they have fleeting are the wishes and efforts of man! allowed some foreigners to take firm How short his time, and consequently how possession of the land. And as foreigners poor will be his results, compared with those have thus in every country beaten some of accumulated by Nature during whole the natives, we may safely conclude that the geological periods! Can we wonder, then, natives might have been modified with that Nature’s productions should be far advantage, so as to have better resisted the “truer” in character than man’s productions; intruders. that they should be infinitely better adapted to the most complex conditions of life, and As man can produce, and certainly should plainly bear the stamp of far higher has produced, a great result by his workmanship? methodical and unconscious means of selection, what may not natural selection It may metaphorically be said that effect? Man can act only on external and natural selection is daily and hourly visible characters: Nature, if I may be scrutinising, throughout the world, the allowed to personify the natural preservation slightest variations; rejecting those that are or survival of the fittest, cares nothing for bad, preserving and adding up all that are appearances, except in so far as they are good; silently and insensibly working, useful to any being. She can act on every whenever and wherever opportunity offers, internal organ, on every shade of at the improvement of each organic being in constitutional difference, on the whole relation to its organic and inorganic machinery of life. Man selects only for his conditions of life. We see nothing of these own good; Nature only for that of the being slow changes in progress, until the hand of which she tends. Every selected character is time has marked the long lapse of ages, and fully exercised by her, as is implied by the then so imperfect is our view into long-past fact of their selection. Man keeps the natives geological ages that we see only that the of many climates in the same country. He forms of life are now different from what seldom exercises each selected character in they formerly were. . . . some peculiar and fitting manner; he feeds a long and a short-beaked pigeon on the same food; he does not exercise a long-backed or long-legged quadruped in any peculiar manner; he exposes sheep with long and

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