Herbert Spencer

by J. Arthur Thomson

Darwin rendered three great services to evolution-doctrine, (1) By his marshalling of the evidences which suggest the doctrine of descent, he won the conviction of the biological world. (2) He applied the evolution-idea to various sets of facts, not only to the origin of species in general, but to the difficult case of Man; not only to the origin of the countless adaptations with which organic nature is filled, but to particular problems such as the expression of the emotions; and in so doing he corroborated the evolution-formula by showing what a powerful organon it is. (3) Along with Alfred Russel Wallace, he elaborated the theory of natural selection, which disclosed one of the factors in the evolution-process.

As we have seen, Herbert Spencer preceded Darwin in his championing of the doctrine of descent, to which the natural mood of his mind, and the influences of Lamarck and von Baer had led him to give his adhesion. He also applied the evolution-formula to an even wider series of facts than Darwin ventured to touch, viz., to the inorganic world and to psychological and sociological facts. It remains to be seen what his position was in regard to the Factors of Organic Evolution.

Spencer's position may be more clearly defined if we first sketch the answer which most biologists would at present give to the question—What are the factors of Organic Evolution?

Variation.—Postulating the powers of growing and reproducing, of acting on and reacting to the environment, postulating also heredity without which no organic evolution is possible, biologists distinguish two sets of factors in the evolution process. On the one hand there are originative factors which produce those changes in living creatures which make them different from their fellows. These changes or observed differences are of two kinds—(a) they may have their origin in the arcana of the germ and be inborn variations (germinal, constitutional, endogenous, etc.), or (b) they may be acquired modifications wrought on the body of the individual by environmental influences or by use and disuse (somatic, acquired, exogenous, etc.). Thus "modifications" or "acquired characters" may be defined as structural changes in the body of the individual organism, directly induced by changes in the environment or in the function, and such that they transcend the limit of organic elasticity and persist after the inducing causes have ceased to operate. Merely transient changes which disappear soon after their cause has ceased to operate may be conveniently called "adjustments." Now when we subtract from the total of observed differences between individuals of the same stock, all the modifications and adjustments which we can distinguish as such by their being causally related to some alteration in function or environment, we have a remainder which we call "variations." We cannot causally relate them to differences in habit or surroundings, they are often hinted at even before birth, and they are not alike even among forms whose conditions of life seem absolutely uniform. This distinction between modifications and variations, though clear in theory, is not always readily drawn in practice, but it is of great importance, for while all innate variations, except complete sterility, are transmissible, and thus may form the raw materials of progress, there is no secure evidence that acquired characters or somatic modifications are transmissible. Therefore, the latter, though very important for the individual, and indirectly important for the race, cannot be assumed (without further proof) as directly important in the transmutation of species.

As to the nature and frequency of inborn variations, Biology has recently begun to accumulate precise observations, and has renounced the bad habit of simply postulating variability without statistically or otherwise defining it. Life is so abundant and so Protean that biologists have tended to draw cheques upon Nature as if they had unlimited credit, scarce waiting in their impetuosity to see whether these are honoured, but the very title—Biometrika—of a new journal shows that the science is emerging from the slough of vagueness in which, to the physicists' contempt, it has so long floundered. All science begins with measurement, and one of the great steps that have been made of recent years is in the tedious, but necessary task of recording the variations which do actually occur. From these we can argue with a clear intellectual conscience back to what may have been. One result is plain, that variation is a very general fact of life; whenever we settle down to measure we find that specific diagnoses are averages, that specific characters require a curve of frequency for their expression, that a living organism is usually like a Proteus. There are no doubt long-lived, non-plastic, conservative types, such as Lingula, where no visible variability can be detected (even in untold ages if we consider the hard parts preservable as fossils), but to judge from these as to the rate of evolutionary change is like estimating the rush of a river from the eddies of a sheltered pool. Another result is that it becomes possible to distinguish between continuous variations, which are just like stages in continuous growth, in which the descendant has a little more or a little less of a given character than its parents had, and discontinuous variations in which a new combination appears suddenly without gradational stages, and with no small degree of perfection. Although there is truth in Lamarck's dictum that "Nature is never brusque," although Jack-in-the-box phenomena are rare, the evidence, e.g. of Bateson and De Vries, as to the frequent occurrence of discontinuous variations appears conclusive. Such words as "freaks" and "sports" express a truth, suggested by Mr Galton's phrase "transilient variations," that organisms may pass with seeming abruptness from one form of equilibrium to another. There is evidence that these sudden and discontinuous variations—"mutations" many of them are called—are often very heritable, that when they appear they come to stay; and it seems likely, especially from facts of breeding and cultivation, that these mutations, rather than the minute "fluctuating" variations, have supplied the raw material on which selection has chiefly operated in the evolution of species.

It also becomes more and more evident that the living creature may vary as a unity, so that if there is more of one character there is less of another, and so that one change brings another in its train. It seems as if the organism as a whole—through its germinal organisation, of course—may suddenly pass from one position of organic equilibrium to another. Thus we are not shut up to the assumption of the piecemeal variation of minute parts; there is greater definiteness and less fortuitousness in variation than was previously supposed. We begin, from actual data, to see the truth of the view which Goethe and Nägeli suggested, that the evolution of organisms is pre-eminently a story of self-differentiating and self-integrating growth,—cumulative, selective, definite, and harmonious—like crystallisation. As to the origin of variations, it must be admitted that until we know the actual facts better, we cannot expect to know much in regard to their antecedents. Many suggestions have been made, some of which may be summarised.

There is something comparable to the First Law of Motion to be read out of the persistence of characteristics from generation to generation. Like tends to beget like. But while the relation of genetic continuity which links generation to generation tends to ensure this persistence, it presents no more than a curb to the occurrence of variation. While complete and perfect inheritance and complete and perfect expression of that inheritance in development would mean the absence of variation, there are many reasons why this completeness of hereditary resemblance is rare. For the inheritance seems to consist of sets of hereditary qualities not in duplicate merely but in multiplicate; they are not all of equal strength or of equal stability; there may be a struggle amongst them; and they are subject to changes induced by the changes in the complex nutritive supply which the parental body—their bearer—affords.

A variation, which makes its possessor different from the parents, is often interpretable as due to some incompleteness of inheritance or in the expression of the inheritance. It seems as if the entail were sometimes broken in regard to a particular characteristic. Oftener, perhaps, as the third generation shows, the inheritance has been complete enough potentially, but the young creature has been prevented from realising its entire legacy. Contrariwise, it may be that the novelty of the newborn is seen in an intensifying of the inheritance, for the contributions from the two parents may, as it were, corroborate one another.

But in many cases a variation turns up which we must call novel, some peculiar mental pattern, it may be, which spells originality, some structural change which suggests a new departure. We tentatively interpret this as due to some fresh permutation or combination of the complex substances which form the material basis of inheritance, and are mingled from two sources at the outset of every life sexually reproduced. It is not merely in an intermingling of maternal and paternal contributions that a life begins, but of legacies through the parents from remoter ancestors. The permutations and combinations may be due to a struggle between the elements which are the bearers of the heritable qualities, or they may be due to fluctuations in the nutritive stream which the body supplies to its germ-cells. It must be remembered that the hereditary material is very complex, and that it has a complex environment within the parental body. In spite of its essential architectural stability, it may have a tendency to instability as regards minor details, and we may perhaps find the change-exciting stimuli in the ceaseless nutritive oscillations within the body, while the mode of restoring a disturbed equilibrium may be through a germinal struggle among the different sets of minute elements which we may call the heritage-bearers. The idea of germinal selection has been elaborated with great subtlety by Prof. Weismann.

Nor does it seem to us legitimate to exclude the possibility that the germ-cell, or the germ-plasm as the essential part of it, may grow into a slightly more differentiated and integrated unity before it begins its task of development. For the power of growth is characteristic of everything living. Enough has been said, however, to indicate how uncertain is the voice of biology in answering the fundamental questions as to the nature and origin of variations.