Life of Charles Darwin

by G. T. Bettany

On the estate of a relative in Staffordshire the changes consequent on planting several hundred acres with Scotch fir were remarkable. In twenty-five years twelve species of conspicuous plants, and six different insectivorous birds had become settled and flourishing inhabitants in the plantations. The characteristic of the philosopher, who sees in the unconsidered trifles of others the material for his choicest discoveries, is well exemplified in his mode of observing the results of enclosure near Farnham, in Surrey. Here a multitude of self-sown firs sprang up in the enclosures, and Darwin went to examine into the cause of the strange phenomenon. Not a fir was in sight except some distant clumps. “But on looking closely between the stems of the heath, I found a multitude of seedlings and little trees, which had been perpetually browsed down by the cattle. In one square yard, at a point some hundred yards distant from one of the old clumps, I counted thirty-two little trees; and one of them, judging from the rings of growth, had during twenty-six years tried to raise its head above the stems of the heath, and had failed.”

The interdependence of animal upon animal, of animal upon plant, of plant upon animal, is enforced in many ways by Darwin. For instance, the visits of humble-bees are of special importance to the welfare of red clover; humble-bees are largely destroyed by field-mice; cats largely destroy field-mice near villages, and so favour humble-bees, and secondarily red clover. Every paragraph of the chapter on the struggle for existence is full of suggestion, and subversive of old imaginings. But Darwin’s knowledge is to him slight, his ignorance profound. Yet, he says, notwithstanding our ignorance, “we may console ourselves with the full belief that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply.”

The great chapter on Natural Selection, or the preservation of favourable and the rejection of injurious variations, is crowded with striking passages. One of these vividly contrasts man’s selection with nature’s. “Man can act only on external and visible characters: nature cares nothing for appearances, except in so far as they may be useful to any being. She can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his own good; nature only for that of the being she tends. Every selected character is fully exercised by her; and the being is placed under well-suited conditions of life.... Under nature, the slightest difference of structure or constitution may well turn the nicely-balanced scale in the struggle for life, and so be preserved. How fleeting are the wishes and efforts of man! how short his time! and consequently how poor will his products be, compared with those accumulated by nature during whole geological periods. Can we wonder, then, that nature’s productions should be far ‘truer’ in character than man’s productions; that they should be infinitely better adapted to the most complex conditions of life, and should plainly bear the stamp of far higher workmanship?” The words in italics certainly are a good answer to those who think Darwin had any tendency to depreciate the marvels of nature by bringing them under the law of natural selection. But we shall gain further light on this subject later on.

The main argument may be summed up thus: if variations beneficial to any creature occur, which cannot be doubted, the individuals in whom they occur will have the best chance of surviving and transmitting their qualities to their offspring. This natural selection will tend to produce divergence of character among offspring, and to intensify differences until they equal those between species or even genera. The same tendency to improvement brings about the decay and ultimate extinction of many lower and unimproved forms of life.

One of the best examples of Darwin’s style is in the passage comparing all members of the same class of beings to a great tree. “I believe this simile largely speaks the truth. The green and budding twigs may represent existing species; and those produced during each former year may represent the long succession of extinct species. At each period of growth all the growing twigs have tried to branch out on all sides, and to overtop and kill the surrounding twigs and branches, in the same manner as species and groups of species have tried to overmaster other species in the great battle for life. The limbs divided into great branches, and these into lesser and lesser branches, were themselves once, when the tree was small, budding twigs; and this connexion of the former and present buds by ramifying branches may well represent the classification of all extinct and living species in groups subordinate to groups. Of the many twigs which flourished when the tree was a mere bush, only two or three, now grown into great branches, yet survive and bear all the other branches; so with the species which lived during long-past geological periods, very few now have living and modified descendants. From the first growth of the tree many a limb and branch has decayed and dropped off; and these lost branches of various sizes may represent those whole orders, families, and genera which have now no living representatives, and which are known to us only from having been found in a fossil state. As we here and there see a thin straggling branch springing from a fork low down in a tree, and which by some chance has been favoured and is still alive on its summit, so we occasionally see an animal like the Ornithorhynchus or Lepidosiren, which in some small degree connects by its affinities two large branches of life, and which has apparently been saved from fatal competition by having inhabited a protected station. As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications.”

What may be the laws controlling or producing variation Darwin candidly tells us he does not know. Some authors, he says, believe it to be as much the function of the reproductive system to produce individual differences, or very slight deviations of structure, as to make the child like its parents. But we certainly do not know the precise effect of any change of conditions, or what changes may be entailed in other parts of an organism by given changes in one part.[9]

Why, if species are continually being modified, do we not see multitudes of transitional forms around us? How can the elaborate structure and special habits of a bat have been formed by the modification of some animal of entirely different habits? How can the marvellous perfections of the human eye or that of one of the higher animals be supposed to have arisen through natural selection? These questions Darwin answers with powerful effect; but for the details we must refer the reader to the book itself. Incidentally he refers to objections urged against the view that every detail of structure has been produced for the good of its possessor. He says plainly that if structures have been created for beauty in the eyes of man, or for mere variety, that is fatal to his theory. Yet he admits that many structures are of no direct use to their possessors; but they have been inherited from ancestors to whom they were of use, or they have arisen as correlated changes or in dependence on some other cause, where use and benefit have been primary.

In dealing with Instinct, we see Darwin personally studying ants and bees in their social habits. The idea of ants making slaves is to him “odious,” which we can well understand after his references to slavery in South America. For three years, during June and July, he watched for many hours several ants’ nests in Surrey and Sussex to see whether the slaves ever left the nest. One day he witnessed a migration of ants from one nest to another, the masters carefully carrying their slaves in their jaws. Again, he saw a party attempting to carry off slaves, succeeding, however, only in carrying their corpses off for food to the nest. Darwin then dug up a small group of pupæ of the slave species from another nest, and put them down near the place of combat. They were eagerly seized and carried off by the tyrants, “who perhaps fancied that, after all, they had been victorious in their late combat.” At the same time the slave-owners were able to distinguish instantly the pupæ of another species, showing much terror at sight of them; yet they ultimately took heart, and carried them off.

The cell-making instinct of the hive-bee, “the most wonderful of all known instincts,” as Darwin terms it, was closely studied. The comb, “so beautifully adapted to its end,” he enthusiastically admired. Yet he finds gradation among bees, and can imagine a method by which this beautiful construction, has been gradually developed. His ideas were tested by setting bees to work on a solid piece of wax between two combs. The detailed account of these experiments is most instructive. It is quite charming to mentally follow the patient experimenter covering the edges of a single cell or the extreme margin of a growing comb with a thin layer of vermilion wax, and soon proving that many bees work in succession at a single cell by the rapid diffusion of the vermilion colouring as delicately as a painter could have done it, atoms of the coloured wax being removed and worked into the growing cells all round.[10] “It was really curious,” Darwin says, “to note in cases of difficulty, as when two pieces of comb met at an angle, how often the bees would entirely pull down and rebuild in different ways the same cell, sometimes recurring to a shape which they had at first rejected.” Here surely he was watching evolution in that slow, gradual process which appears to be the rule.

The castes of neuter ants, constituting as they did “by far the most serious special difficulty” Darwin had encountered, were similarly studied; but, as expected, gradations were found connecting them, although the extremes differ markedly in shape and size. The case is most interesting, because these castes could only be developed if the variations which produced them were profitable to the community; “for no amount of exercise, or habit, or volition, in the utterly sterile members of a community could possibly have affected the structure or instincts of the fertile members, which alone leave descendants.” This fact Darwin considers to be demonstrative against Lamarck’s doctrine. At the same time, he admits that instincts are not always perfect, and are liable to make mistakes; and that no instinct has been produced for the exclusive good of other animals, but that each animal takes advantage of the instincts of others. It is to him “far more satisfactory to look at such instincts as the young cuckoo ejecting its foster-brothers, ants making slaves, the larvæ of ichneumonidæ feeding within the live bodies of caterpillars, not as specially endowed or created instincts, but as small consequences of one general law, leading to the advancement of all organic beings, namely, multiply, vary, let the strongest live and the weakest die.” And here Darwin strikes one of his truest and most helpful notes. It is far more satisfactory to contemplate the rapine and war of nature as incidents which aid in working out a grand progress than as multitudinous cruelties, working no good, and in past ages of unknown length merely preluding the struggle and rapine through which man works out his rise or fall. If we agonise that we and our descendants may rise, life is worth living.