Survival of the species

“ But animals or plants which thus differ in a state of nature are always classed as distinct species, and thus we see how, by the continuous survival of the fittest or the preservation of favoured races in the struggle for life, new species may be originated. ”

“ But the use of the word "Survival" should have sufficed to indicate that the real point of application of the force by which Nature modifies species and raises the average in any quality, lies not in selective breeding, but in the disproportionately numerous deaths of the individuals below the average. ”

“ The organism plays its new card in the game of life, and the consequences may determine survival. The relatively less fit to given conditions will tend to be eliminated, while the relatively more fit will tend to survive. If the variations are hereditary and reappear, perhaps increased in amount, generation after generation, and if the process of sifting continue consistently, the result will be the evolution of the species. ”

“ In natural processes it bears the title of survival of species. The fact that recent types show large numbers, and in some instances even hundreds of minor constant forms, while the older genera are considerably reduced in this respect, is commonly explained by the assumption of extinction of species on a correspondingly large scale. ”

“ This preservation of favourable individual differences and variations, and the destruction of those which are injurious, I have called Natural Selection, or the Survival of the Fittest. ”

“ The very essence of the theory of protective resemblance, as a means of survival consequent upon the slow but sure action of natural selection, is a special, not a general effect,—a particular, not an universal attribute,—but one of the many and diverse qualifications which enable animals and plants to survive in the competitive struggle for existence. ”

“ A propos to this point, I do not believe that anyone yet has half done justice to natural selection in respect of its action subsequent to the formation of species—at least, not expressly. But I must shut up. ”

“ On both sides, then, is Nature just, for though she does her best to keep living species extant until evolved into higher forms of life, she permits each species to prey on the overgrowth or overplus of others that it may live. ”

“ This general sketch of the enrichment of the earth with flowering plants, insects, and birds in the Tertiary Era is all that the limits of the present work permit us to give. It is an age of exuberant life and abundant food; the teeming populations overflow their primitive boundaries, and, in adapting themselves to every form of diet, every phase of environment, and every device of capture or escape, the spreading organisms are moulded into tens of thousands of species. We shall see this more clearly in the evolution of the mammals. ”

“ We may judge, then, of the amount of extermination that goes on among those animals which produce embryos by the thousand or even the hundred thousand. The effects of this enormous death-rate on the progress of the race or species we shall have to consider in the next chapter, when the question of the differentiation of species is before us. ”

“ Naturalists may fairly ask men to remember that each of these species which we are forced to destroy represents the toil and pains of unimaginable ages, and that when these creatures are swept away they can never be recovered. Whatever new species may come, by processes of evolution from the life which remains after we have done our will with the wilderness, we shall never see again the forms which have passed away. ”

“ Here we see that the case of domestic animals was already present in his mind as bearing on the production of natural species. The disappearance of intermediate forms naturally leads up to the subject of extinction, with which the next extract begins. ”

“ These responses have been fixed in the species through adaptation to environment. Natural selection has compelled the animal automatically to respond in a fixed manner and a certain way to all the usual external stimuli it encounters in the course of a usual life. ”

“ But it is the object of the present paper to show that this assumption is altogether false, that there is a general principle in nature which will cause many varieties to survive the parent species, and to give rise to successive variations departing further and further from the original type, and which also produces, in domesticated animals, the tendency of varieties to return to the parent form.
The life of wild animals is a struggle for existence. ”

“ The theory of natural selection rests on two classes of observable facts: first, that all plants and animals are engaged in a perpetual struggle for existence, there being in every generation of every species a great many more individuals born than can possibly survive ”

“ This will expose the species to new dangers, and require special modifications of structure to meet them. Greater swiftness, increased cunning, nocturnal habits, change of colour, or the power of climbing trees and living for a time on their foliage or fruit, may be the means adopted by different species to bring themselves into harmony with the new conditions ”

“ We can see that any form which is represented by few individuals will run a good chance of utter extinction, during great fluctuations in the nature or the seasons, or from a temporary increase in the number of its enemies. ”

“ Nature (or its Author) , in creating the animals, has foreseen all the possible kinds of circumstances in which they should live, and has given to each species an unchanging organization, as also a form determinate and invariable in its different parts, which compels each species to live in the places and in the climate where we find it, and has there preserved its known habits. ”

“ Allowing for some original specific difference which we can hardly hope to discover, the changes that have taken place may be considered as the result of adaptation to those habits of life under which our species (now ranking zoologically as a Family) has been developed. And this adaptation I shall assume to have been brought about under conditions of natural selection: human races, as we now see them, being the survivors of many variations, more or less successful, and the others having been destroyed. ”

“ In the struggle it would have a better chance of surviving, and those of its offspring which inherited the variation, let it be ever so slight, would have a better chance to survive. Yearly more are bred than can survive; the smallest grain in the balance, in the long run, must tell on which death shall fall, and which shall survive{233}. Let this work of selection, on the one hand, and death on the other, go on for a thousand generations ”

“ The unfit perish and the fit survive, everything depending upon the relative success of the organism in adapting itself to the conditions under which it is endeavoring to live. The clumsy mastodon became extinct; his bones are now relics in museums; but the horse, being fleet of foot, managed to survive. The fit organisms,—plants or animals or human beings,—have survived and have perpetuated the species. They gave to their offspring the traits or qualities which enabled themselves to survive. ”

“ If the coming in of one new species, and the loss of one other which had endured for ages, should take place annually, still, assuming that there are a million of animals and plants living on the globe, it would require, I observed, a million of years to bring about a complete revolution in the fauna and flora. ”

“ Extinction.—This subject will be more fully discussed in our chapter on Geology; but it must be here alluded to from being intimately connected with natural selection. Natural selection acts solely through the preservation of variations in some way advantageous, which consequently endure. ”

“ Thus, then, when science—which, if it is truly scientific, makes no distinction of value, moral or spiritual, between man and the sparrow—has explained that a given species which did survive was the only species that could have survived under the conditions, there still remains the problem, for those to whom it is a problem, Why should the species which was bound to survive also happen to be a species of a higher type? ”

“ Moreover, each species on the confines of its range, where it exists in lessened numbers, will, during fluctuations in the number of its enemies or of its prey, or in the nature of the seasons, be extremely liable to utter extermination ”

“ They might, for instance, be better able to endure the cold or heat or changes of the climate; better able to find nourishment from what surrounded them; better able to escape from or resist other species which fed upon them; better fitted to attract or master the other sex. Being thus liable to die, their numbers relatively to other species would increase; and that very increase in their numbers might tend towards the extinction of those other species. ”

“ Let us first consider what will be the effect of the struggle for existence upon the animals and plants which we see around us, under conditions which do not perceptibly vary from year to year or from century to century. We have seen that every species is exposed to numerous and varied dangers throughout its entire existence, and that it is only by means of the exact adaptation of its organisation—including its instincts and habits—to its surroundings that it is enabled to live till it produces offspring which may take its place when it ceases to exist. ”

“ Finally, I wish to call attention to the fact that natural selection is constantly acting through the law of the survival of the fittest, in such a way as to bring each organism into more and more perfect harmony with its environment; that is, it is constantly bringing about a more and more exact, definite, and perfect adjustment between external and internal relations. ”

“ Stated concretely in regard to living creatures, the general doctrine of organic evolution suggests, as we all know, that the plants and animals now around us—with all their fascinating complexities of structure and function, of life-history, behaviour, and inter-relations—are the natural and necessary results of long processes of growth and change, of elimination and survival, operative throughout practically countless ages ”

“ Looking to the future, we can predict that the groups of organic beings which are now large and triumphant, and which are least broken up, that is, which have as yet suffered least extinction, will, for a long period, continue to increase. ”

“ But we will concede that every creature bore a charmed life, that it might not perish by famine or violence till it had propagated its kind. We should then expect to observe that species had distributed themselves over the globe in lines either tortuous or direct, single or branching, broad or narrow, but all diverging from a common centre. ”

“ If species have died out slowly and naturally in the history of the earth, and new species have made their appearance at the same time, may not these new species have arisen slowly and naturally? Suppose these simple and purely natural causes, that had brought about the extinction of certain species, had been for others the very starting-point of development? ”

“ It is the rule, the law of nature, and it reaches its fullest development with the higher vertebrates. Those species which live solitary, or in small families only, are relatively few, and their numbers are limited.” [111] “Life in societies enables the feeblest insects, the feeblest birds, and the feeblest mammals to resist, or to protect themselves from, the most terrible birds and beasts of prey; it permits longevity; it enables the species to rear its progeny with the least waste of energy, and to maintain its numbers, albeit with a very slow birth-rate ”

“ If this diversity of action in the nerve-ends proved of no service to the animal, it would go no further, because those individuals who possessed it would not be favored beyond those who did not. But if it proved useful, as it undoubtedly would do to flower-haunting insects, natural selection would insure its survival and its constant increase from generation to generation. ”

“ When they die out—as sooner or later any species may—the verdict must be accidental death, under stress of adverse circumstances, not exhaustion of vitality; and, commonly, when the species seems to die out, it will rather have suffered change. ”

“ The Creator has bountifully stored the earth and the ocean with animals and vegetables. Our attention is here circumscribed to the most exalted class, the Human Species; leaving to the naturalist a description of quadrupeds, birds, fishes, insects, and vegetables. By far the largest proportion of the human species are stationed to the north side of the equator, and even to the north of the tropick of cancer. ”

“ We have seen, in Chapter X., how important an agent in producing extinction and modification of species must have been the repeated changes from cold to warm, and from warm to cold conditions, with the migrations and crowding together that must have been their necessary consequence. ”

“ Such protective resemblances are obviously of great value to animals, and, like other advantageous modifications, have been produced by the action of natural selection. Those individuals of a species most conspicuous and hence most readily perceived by enemies are the first (under ordinary circumstances) to be captured and eaten. The less conspicuous live and produce young like themselves. ”