The principle explains what no other hypothesis has ever done, not only Nature’s perfection, which, in the hour of ease, we are ready to believe in, but what has hitherto been a much greater puzzle to those who knew of its existence, Nature’s imperfection. The whole creation is in constant travail to bring forth something better than its present best. The products of man’s reason are not, you will readily admit, always perfect, and yet man’s reason is a part of the creation, and of nature’s work. The waste of life is prodigious, if such a term is applicable to the circumstance that often millions of spores are produced in order that half a dozen plants may grow; millions of eggs in the roe of a fish, in order that the parents may be represented by three or four individuals. The bee defends itself by its sting, but its weapon of defence is fatal to itself. Were a merchant habitually to send five or six million articles of merchandize across the Atlantic on the bare possibility that five or six articles out of the number might reach their destination; or, were a father to arm his son with a weapon on the presumption that the first time he used it, it would cost him his life; you would think the man mad, not wise. Yet, if the astonishing fecundity of the braken, the mushroom, and the codfish, if the sting of the bee with its backward serratures, be the products of direct creation, the analogy is somewhat telling. How different, on the other hand, must our judgment be of those contrivances, when we trace them to the simple, primary, beneficent law of natural selection, working always steadily for the good of each species, and so working, that we may feel tolerably sure that when any species dies out and disappears, it has been replaced by something better. For by this law, we see that fertility itself is a character which will be selected as tending to the preservation of a species, and that many creatures must have acquired the power of what looks like wasteful reproduction in the long-continued struggle for existence. We can see, too, how in that same struggle, it may have proved expedient for a creature to be armed with a weapon capable of inspiring terror, yet so contrived that its possessor should, of necessity, be peaceful towards its neighbours. True, this might have been done by a single act of creation, but why, then, was it not done also in the case of the mosquito, the wasp, and the hornet?
On the theory of sudden creation, how can we account in any but an arbitrary manner, for the innumerable cases in which slight differences separate various species; for the confused neutral ground between different classes, as where, for example, a creature seems half animal half plant; for the isolation of many forms from the stations they are admirably fitted to occupy; for the fact that many creatures are hideous, weak, timid, violent, and venomous; for the imperfection of an instinct in one species found perfected in another, which Mr. Darwin exemplifies by comparing the cells of the humble-bee, the melipona domestica of Mexico, and the hive-bee, ranging from great simplicity to an extreme perfection[13]? But the principle of natural selection offers a solution to every one of these enigmas. It embraces all the various phases of life of the ancient world as well as the modern, and gives a key to the whole grand uninterrupted plan. It carries back the mind to a period when the earth was destitute of life; when yet, as it were, the thought in the Divine mind was still unspoken, that of one, and that as good as dead, should spring seed like the sand which is upon the sea-shore for multitude. Then it came to pass that the dust of the earth was called into life by the Life-Giver, and received the strange command and the mysterious power to multiply, and to replenish the earth. As soon as living creatures multiplied to any great extent, they would spread themselves into different lands and seas and climates; they would find different sources of nourishment, and then variation would come into play, and close upon variation would follow selection, not of necessity destroying the old forms, but establishing new ones, because in some stations the form that had not varied might thrive best, in others the variety would have an advantage[14]. As time went on, through the constant changes that the surface of the globe is undergoing, one variety would be isolated from another, and in such an isolation the differences would increase. And the more a species varied, the more fitted it might become for some habitat, from which it was completely cut off by a chain of mountains, a rapid river, or a deep sea. As the competition became more intense, variations would become more and more valuable, enabling creatures to occupy positions before untenable, ocean-depths, sandy shores, holes in rocks, fresh-water lakes, tops of mountains, branches of trees, the bodies of other living beings. Some would be taught by necessity and enabled by favourable variations to prey, as well as take up their abode, on other creatures. And as the strife became more and more urgent, all sorts of qualities that from our point of view may seem noxious and degrading might prove of the highest service and advantage to their own possessors. Plants with sharp thorns and envenomed hairs, poisonous snakes, trichinæ and other parasites horrible to man, would find their advantage at our cost, or by unparalleled fertility would defy all efforts to extirpate them. Some species would profit by minuteness, others by size; others, in various ways, by talons, beak, thread-like tongue, prehensile tail, or furry coat; and, just as men are said to go through fire and water for the sake of money, so for the sake of preservation, no habit, no locality would be too uncongenial for a species to develope adaptation thereunto. And, accordingly, we find that the water-ouzel, which is a species of thrush, subsists entirely by diving; there is a tree-climbing lobster in the Mauritius; there are fishes which ramble about on the land, and one fish, the anabas scandens, can climb eight or ten feet up the trunk of a palm[15].
The choice of food, the choice of habitation, the construction of dwelling-places for themselves or their offspring, methods of defence, methods of attack, are variously carried out by myriads of species. The processes employed, in man we call for the most part rational; in the lower animals we call them instinctive; but there are processes employed for these self-same objects by vegetables as well as by men. For plants, in one sense stationary, travel towards water by their roots, towards light by their branches; they assimilate the elements of nutriment that suit them, rejecting others. The Sensitive plant shrinks from the touch, Venus’s fly-trap closes round unwary insects and destroys them. Tendrils fasten on the supports that are offered them. Trees keep in their delicate blossoms till the weather is genial. Many a corolla folds carefully round stamens and pistils when the chilly twilight approaches.
Pass from proceedings like these to the swimming movements of a beheaded Dytiscus[16], and other reflex actions in animals, to the food-seeking movements of the tentaculæ of the Hydra or fresh-water Polype, which hover doubtfully between reflex and instinctive action: go forward through the innumerable gradations of instinct till you come, for instance, to the spider, weaving its symmetrical web, rushing out of its lair to seize the prey when the web is shaken lightly, but keeping itself close from a too dangerous foe when the web is vehemently shaken. Examine the nest of the Mygale (the trap-door spider) lined with silken tapestry, furnished with a door on a silken hinge, which it covers above with materials like the surrounding soil, and holds from beneath against an intruder, by applying its claws to the most advantageous point, the point most distant from the hinge: consider the little Sylvia Sutoria, or tailor-bird, which draws filaments of cotton from the cotton-plant, and sews leaves together with its beak and feet to form a nest; go to the huts and river-dams of the beaver; attend a conclave of rooks judging an offender; look into the hive of the hive-bee; observe the conscious vanity of the peacock; preach liberty to the slave-making ants; watch the sagacious ways of dogs and horses; and then lastly see if it be possible to resist the conclusion that, were all forms that ever existed, from the earliest geological times to our own, present before us in the order of their genealogies, we should see them to be the members of a single family, now, indeed, immensely divergent, yet all united by some affinity or affinities, whether dimly or conspicuously shown.
How strangely men and beasts are united by similarity of blood and fibre! How strangely fishes, birds, and mammals by the likeness of the vertebrate skeleton! How strangely plants and animals by the phenomena of generation, not only in the union of the sexes, but also in (agamogenesis) or asexual reproduction! Need we wonder at community of origin between a coral and a cactus, a whale and a sloth, a wolf and a Shylock, when we find that a lady’s silken tresses, the bristles of a boar, the quill of the porcupine, the feathers of the owl, and the horns of the buffalo, are parallel and specifically interchangeable developments?
Consider the vine, with its stem, branches, twigs, roots, rootlets, leaves, tendrils, and the luscious grapes of the ripe cluster. From one seed sprang all of these. On the bough of an orange tree there live and grow together leaf and petiole, flower and fruit, the green unripe fruit, the yellow and the golden-ripe. All these from one seed. Yet there is no jealousy among them. No one disowns a kindred origin for the root of the tree and its golden fruit, utterly unlike as these are, but, like so many other utterly unlike things in this world, sprung from the same germ.
To have produced and accumulated the vast divergences that now exist, a lapse of time, indeed, must be conceded, unmeasured and perhaps immeasurable; but this lapse of time is precisely what geology, independently of Darwinism, has already demanded. As the Scriptures speak of the earth as immoveable, because so it is in reference to the senses of man, they speak also of the everlasting mountains, and with them the rocks are a type of the eternal: compared with the life of man these expressions are truthful and well-chosen, but they do not mean to say the rocks are as eternal as God, nor yet everlasting compared with the existence of the globe. It may have taken ten thousand centuries to rear up a mountain, and yet, if we reckon the age of the globe on the scale of a man’s life, the mountain be but of yesterday.
The immense antiquity, not only of the globe, but of that thin crust of it open to our inspection, has been ascertained by geology. Geology, again, has made it certain that during millions of years, changes on the earth’s surface have been in continual progress, so that not once merely, but many times over, continents and oceans must have yielded to one another, yet by no sudden, but ever by a gradual transposition, such as is in constant progress at the present day.
Seeing that the dwelling-place of living creatures is thus continually and continuously changing, how clumsy an arrangement it would have been had the forms of life been made constant, instead of being endowed, as they clearly have been, with a wonderful power of adaptation. The question, be it remembered, is not for a moment whether God has made the universe, but how He has made that portion of it which He has enabled us to see and examine. Nor yet, to be thoroughly accurate, is it in question how He has worked, but how He has been pleased to exhibit His operations to the reasoning minds of men. What is worthy of God we cannot indeed judge. We can only believe that the things which are, stand worthiest of His wisdom and goodness, whatever faults may seem in them to our rashly-judging short-sightedness. But comparing theories of creation according to human notions, is it a nobler conception that God should have made successively groups of beings to fill the world, and then swept them away to make room for others nearly like them; each time, as it were, improving on His first idea, and so arguing the imperfection of what had gone before by the very improvement of what followed; or that, foreseeing the perfect types from the beginning, He should have called into existence seeds of life capable, under the laws He gave them, of rising in successive generations through countless ages, to endowments of the noblest order, to a conscious life, to a reasoning faculty, to a moral sense, to a knowledge of God? In such an origin there is for man no degradation, since the lowliness of his parentage has ever been traced back to the dust of the ground; and the lowest form of life is higher in our imaginations than the dull brute earth. Indeed, if we desire to exalt our self-appreciation, whether is it grander for us to have been the work of an instant, or to have been elaborated with Divine care through millions of ages? Will not any miracle in our behalf, however stupendous, seem more credible on the latter than on the former supposition? When we see what Development has already done for the human species, we can the more readily imagine what, under the same Lawgiver, it may do in the future for the individuals of our race. When we find it possible or probable that our own bodies contain resemblances to ancestors enormously remote in time, simply because they contain atoms from the bodies of those very ancestors living again in ourselves, we can understand how in a future, whether near or enormously remote, atoms from the very body of the man that dies may be called into a renewed existence, and clothed again with all that is necessary to personal identity, though haply more transformed and higher raised above the old self, than would be an orang-outang or a naked savage, were either of these enabled to combine the chivalric courtesy of Sir Philip Sydney with the genius of Sophocles and Shakespeare.