The Whence and the Whither of Man / A Brief History of His Origin and Development through Conformity to Environment; Being the Morse Lectures of 1895

An army is more than a mob of individuals; it is individuals plus organization, discipline, authority. A republic is not square miles of territory and thousands or millions of inhabitants. It is these plus organization, central government. Webster claimed that the central government was, and had to be, before the states. The organism cannot exist without its parts; it has a very real existence in and through them. It can coerce them. The state may be an abstraction, but it is one against which it is usually fatal to rebel, and which can say to a citizen, Go and be hanged, and he straightway mounts the scaffold. Now these are analogies and prove nothing. But in so far as they throw light on the essential idea of an organism, they may aid us in gaining a right view of our "cell republic."

Says Whitman in a very interesting article on the "Inadequacy of the Cell-Theory": "That organization precedes cell-formation and regulates it, rather than the reverse, is a conclusion that forces itself upon us from many sides." "The structure which we see in a cell-mosaic is something superadded to organization, not itself the foundation of organization. Comparative embryology reminds us at every turn that the organism dominates cell-formation, using for the same purpose one, several, or many cells, massing its material and directing its movements, and shaping its organs as if cells did not exist, or as if they existed only in complete subordination to its will, if I may so speak. The organization of the egg is carried forward to the adult as an unbroken physiological unity, or individuality, through all modifications and transformations." And Wilson, Whitman, Hertwig, and others urge "that the organism as a whole controls the formative processes going on in each part" of the embryo. And many years ago Huxley wrote, "They (the cells) are no more the producers of the vital phenomena than the shells scattered along the sea-beach are the instruments by which the gravitative force of the moon acts upon the ocean. Like these, the cells mark only where the vital tides have been, and how they have acted."[17]

"Interaction of cells" can help us but little. For how can neighboring cells direct others placed in a new position? The expression, if not positively misleading and untrue, is at the best only a restatement of fact. It certainly offers no explanation. Flood-tide is not due to the interaction of particles of water, though this may influence the form of the waves.

The centre of control is therefore not to be sought in individual cells, whether germ-cells or somatic, but in the organism. And it is the whole organism, one and indivisible, which controls in germ, embryo, and adult, in egg and owl. This individuality, or whatever you will call it, impresses itself upon developing somatic cells, moulding them into appropriate organs, and upon germ-cells in process of formation, moulding them so that they may continue its sway. The muscle, modified by use or disuse, is a better expression of the individuality of its possessor, and the same individuality moulds similarly and simultaneously the germ-cells. Both are different expressions or manifestations of the same individuality. Only slowly does the individuality mould the muscles and nerves of the adult body to its use. Still more slow may be the moulding of the still more refractory germ-plasm, if such there be. But the moulding process goes on parallel in the two cases.

But Weismann's argument rests not merely upon any difficulty or impossibility of the transmissibility of acquired characteristics. His argument is rather that all facts can be better explained by his theory without postulating or accepting such transmission, cases of which have never been absolutely proven. But the question is not whether his theory offers a possible explanation of the facts, but whether it is the most probable explanation of all the facts. No one would deny, I think, that the continuity of the germ-plasm offers the best and most natural explanation of heredity; and that variations could be produced by the influence on the germ-plasm of external conditions seems entirely probable.

But when we consider the aggregation of these variations in a process of evolution, his theory seems unsatisfactory. We have already seen that what we commonly call a variation involves not one change, but a series of changes, each term of which is necessary. Muscle, nerve, and ganglion must all vary simultaneously and correspondingly. Correlation and combination are just as essential as variation. And evolution often demands the disappearance of less fit structures just as much as the advance of the fittest. Says Osborne, "It is misleading to base our theory of evolution and heredity solely upon entire organs; in the hand and foot we have numerous cases of muscles in close contiguity, one steadily developing, the other degenerating." Weismann offers the explanation that "if the average amount of food which an animal can assimilate every day remains constant for a considerable time, it follows that a strong influx toward one organ must be accompanied by a drain upon others, and this tendency will increase, from generation to generation, in proportion to the development of the growing organ, which is favored by natural selection in its increased blood-supply, etc.; while the operation of natural selection has also determined the organ which can bear a corresponding loss without detriment to the organism as a whole."[18]

Here again natural selection of individuals, not the diminished supply of nutriment, has to determine which of many muscles shall be poorly fed and which favored. But natural selection can favor special organs only indirectly through the individuals which possess such organs. Variation is fortuitous, and there is nothing, except natural selection, to combine or direct them. And, I think, we have already seen that any theory which neglects or excludes such directing and combining agencies must be unsatisfactory and inadequate. Weismann has promised us an explanation of correlation of variation in accordance with his theory; and if such an explanation can be made, it would remove one of the strongest objections. But for the present the objection has very great weight.

Furthermore, as Osborne has insisted, linear variations, or variations proceeding along certain single and well-marked lines, would seem inexplicable by, if not fatal to, Weismann's theory. And yet Osborne, Cope, and others have shown that the teeth of mammals have developed steadily along well-marked lines. They have apparently not resulted at all by selection from a host of fortuitous variations.

Says Osborne in his "Cartwright Lectures"[19]: "It is evident that use and disuse characterize all the centres of evolution; that changes of structure are slowly following on changes of function or habit. In eight independent regions of evolution in the human body there are upward of twenty developing organs, upward of thirty degenerating organs." Now this parallelism, through a long series of generations, between the evolution of organs, their advance or degeneration, and the use or disuse of these same organs, that is, of the habits of the individual, is certainly of great significance. It must have an explanation; and the most natural one would seem to be the transmission of the effects of use and disuse.

On the whole Osborne's verdict would seem just: The Neo-Lamarckian theory fails to explain heredity, Weismann's theory does not explain evolution. But, if the effects of use and disuse are transmitted, correlation of variation is to be expected. Muscle, nerve, and ganglion all vary in correlation because they are all used together and in like degree. Evolution and degeneration of muscles in hand and foot go on side by side, because some are used and some are disused. Centres of use and disuse must be centres of evolution. And there would be as many distinct centres of evolution in different parts of the body as there were centres of use and disuse. And between these centres there might be no correlation except that of use and disuse. Brain, muscles, and jaws would develop simultaneously in the ancestors of insects. And the effects of use and disuse, transmitted through a series of generations, would be cumulative. The species advances rapidly because all its members have in general the same habits; the same parts are advancing or degenerating, although at different rates, in all its individuals. An animal having an organ highly developed is far less likely to pair with one having a lower development of the same organ. The Neo-Lamarckian theory supplies thus what is lacking in the Neo-Darwinian.

In lower forms, like hydra, of simple structure and comparatively few possibilities of variation, natural selection is dominant. In higher forms, like vertebrates, and especially in man, it is of decidedly subordinate value as a promoter of evolution. For man, as we have seen, is a marvellously complex being. The great difficulty in his case is not so much to quickly gain new and favorable variations as to keep all the organs and powers of the body steadily advancing side by side. Natural selection has in man the important but subordinate position of the judge in a criminal court, to pronounce the death verdict on the hopeless and incorrigible.

Both Neo-Darwinians and Neo-Lamarckians have erred in being too exclusively mechanical in their theories. It is the main business of the scientific man to discover and study mechanisms. But he must remember that mechanism does not produce force, it only transmits it. If he maintains that he has nothing to do with anything outside of mechanism, that the invisible and imponderable force lies outside of his domain, he has handed over to metaphysics the fairest and richest portion of his realm. In our fear of being metaphysical we have swung to another extreme, and have lost sight of valuable truth which lay at the bottom of the old vitalistic theories. Cells, tissues, and organs are but channels along which the flood of life-force flows. Boveri has well said, "There is too much intelligence (Verstand) in nature for any purely mechanical theory to be possible."

Each theory contains important truth. Nägeli's view of the importance of initial tendencies, inherent in the original living substance, is too often undervalued. My own conviction, at least, is steadily strengthening that, without some such original tendency or aim, evolution would never have reached its present culmination in man. His error lies in emphasizing this factor too exclusively. The fundamental proposition of Weismann's theory, that heredity is due to continuity of germ-plasm, seems to contain important truth. But we need not therefore accept his theory of a germ-plasm so isolated and independent as to be beyond control or influence by the habits of the body. The importance of use and disuse, and the transmissibility of their effects, would seem to supply a factor essential to evolution. Weismann has done good service in emphasizing the stability of the germ-plasm. Evolution is always slow, and, for that very reason, sure.

If these conclusions are correct, they have an important practical bearing. Struggle and effort are essential to progress. Not inborn talent alone, but the use which one makes of it, counts in evolution. The effects of use and disuse are cumulative. The hard-fought battle of past generations becomes an easy victory in the present, just because of the strength acquired and handed down from the past struggle. Persistent variation toward evil is in time weeded out by natural selection. And, while evil remains in the world, we are to lay up stores of strength for ourselves and our descendants by sturdily fighting it. But the effects of right living through a hundred generations are not overcome by the criminal life of one or two. Evil surroundings weigh more in producing criminals than heredity, and their children are not irreclaimable.

The struggles and victories of each one of us encourage the rest. There is, to borrow Mr. Huxley's language, not only a survival of the fittest, but a fitting of as many as possible to survive. And in the midst of the hardest struggle there is the peace which comes from the assurance of a glorious triumph.

FOOTNOTES:

[13] See Nägeli, "Theorie der Abstammungslehre," p. 18; also pp. 12, 118, 285.

[14] Essays upon Heredity, p. 105.

[15] Weismann, Essays, p. 286.

[16] Weismann, Essays, pp. 85 and 171.

[17] See articles by Whitman and Wilson, Journal of Morphology, vol. viii., pp. 649, 607, etc.

[18] Weismann, Essays, p. 88.

[19] American Naturalist, vols. xxv. and xxvi.

[TABLE OF CONTENTS]

Condensed Chart of Development of the Main Line of the Animal Kingdom leading to Man.

PHYLOGENETIC CHART OF PRINCIPLE TYPES OF ANIMAL LIFE.

[TABLE OF CONTENTS]

INDEX