Another argument is the old, suggestive, and really important one urged by Kolliker, that "inorganic nature shows a natural system among minerals (crystals) just as much as animals and plants do, yet in the former there can be no question of any genetic connection in the production of forms."
Yet another argument is found in the occurrence of "inversions" and anomalies in the palaeontological succession of forms, which to some extent upsets the Darwinian-Haeckelian genealogical trees. (Thus there are forms in the Cambrian whose alleged ancestors do not appear till the Silurian.
Foraminifera and other Protozoa do not appear till the Silurian.)
From embryology in particular, as elsewhere in general, we read the "fundamental biogenetic law," that evolution is from the general to the special, from the imperfect to the more perfect, from what is still indefinite and exuberant to the well-defined and precise, but never from the special to the special. According to Hamann"s hypothesis we must think of evolution as going on, so to speak, not about the top but about the bottom. The phyla or groups of forms are great trunks bearing many branches and twigs, but not giving rise to one another. Still less do the little side branches of one trunk bear the whole great trunk of another animal or plant phylum. But they all grow from the same roots among the primitive forms of life. Unicellulars these must have been, but not like our "Protists." They should be thought of as primitive forms having within themselves the potentialities of the most diverse and widely separate evolution-series to which they gave rise, as it were, along diverging fan-like rays.
It would be instructive to follow some naturalist into his own particular domain, for instance a palaeontologist into the detailed facts of palaeontology, or an embryologist into those of embryology, in order to learn whether these corroborate the a.s.sumptions of the Theory of Descent or not. It is just in relation to these detailed facts that criticisms or even denials of the theory have been most frequent. Koken, otherwise a convinced supporter of the theory, inquires in his "Vorwelt," _apropos_ of the tortoises, what has become of the genealogical trees that were scattered abroad in the world as proved facts in the early days of Darwinism. He a.s.serts, in regard to _Archaeopteryx_, the instance which is always put forward as the intermediate link in the evolution of birds, that it does not show in any of its characters a fundamental difference from any of the birds of to-day, and further, that, through convergent development under similar influences, similar organs and structural relations result, iterative arrangements which come about quite independently of descent. He maintains, too, that the principle of the struggle for existence is rather disproved than corroborated by the palaeontological record.
In embryology, so competent an authority as O. Hertwig-himself a former pupil of Haeckel"s-has reacted from the "fundamental biogenetic law." His theory of the matter is very much that of Hamann which we have already discussed; development is not so much a recapitulation of finished ancestral types as the laying down of foundations after the pattern of generalised simple forms, not yet specialised; and from these foundations the special organs rise to different levels and grades of differentiation according to the type.(29) But we must not lose ourselves in details.
Looking back over the whole field once more, we feel that we are justified in maintaining with some confidence that the different p.r.o.nouncements in regard to the detailed application and particular features of the Theory of Descent, and the different standpoints that are occupied even by evolutionists, are at least sufficient to make it obvious that, even if evolution and descent have actually taken place, they have not run so simple and smooth a course as the over-confident would have us believe; that the Theory of Descent rather emphasises than clears away the riddles and difficulties of the case, and that with the mere corroboration of the theory we shall have gained only something relatively external, a clue to creation, which does not so much solve its problems as restate them. The whole criticism of the "right wing," from captious objections to actual denials, proves this indisputably. And it seems likely that in the course of time a sharpening of the critical insight and temper will give rise to further reactions from the academic theory as we have come to know it.(30) On the other hand, it may be a.s.sumed with even greater certainty that the general evolutionist point of view and the great arguments for descent in some form or other will ultimately be victorious if they are not so already, and that, sooner or later, we shall take the Theory of Descent in its most general form as a matter of course, just as we now do the Kant-Laplace theory.
CHAPTER V. RELIGION AND THE THEORY OF DESCENT.
In seeking to define our position in regard to the theory of descent it is most important that we should recognise that, when it is looked into closely, the true problem at issue is not a special zoological one, but is quite general, and also that it is not a new growth which has sprung up suddenly and found us unprepared, but that it is very ancient and has long existed in our midst. In the whole theory the question of "descent" is after all a mere accessory. Even if it fell through and were seen to be scientifically undemonstrable, "evolution in the realm of life" would remain an indisputable fact, and with it there would arise precisely the same difficulties for the religious interpretation of the world which are usually attributed to the Theory of Descent.
Evolution or development has been a prominent idea in the history of thought since the time of Aristotle, but descent is, so to speak, a modern upstart. According to long-established modes of thought, to _evolve_ means to pa.s.s from d???e? to ??e??e?a e??a?, from _potentia_ to _actus_, from the existence of the rudiment as in the seed to full realisation as in the tree. In the course of its development the organism pa.s.ses through many successive phases, which are related to one another like steps, each rising directly from the one beneath, and preparing for the one above.
Thus all nature, and especially the realm of life, implies a ladder of "evolution." What is "potentially" inherent in the lowest form of life has in the highest, as in man, become actual or "realised" through a continuous sequence of phases, successively more and more evolved. This view in its earlier forms was very far from implying that each higher step was literally "descended" from the one below it, through the physical and mental transformation of some of its representatives. As the world, in Aristotle"s view for instance, had existed from all eternity, so also had the stages and forms of life, each giving rise again to its like. Indeed, the essential idea was that each higher step is simply a development, a fuller unfolding of the lower stage, and finally that man was the complete realisation of what was potentially inherent in the lowest of all.
This doctrine of evolution was in modern times the fundamental idea of Leibnitz and Kant, of Goethe, Sch.e.l.ling and Hegel. It brought unity and connectedness into the system of nature, united everything by steps, denied the existence of gaping chasms, and proclaimed the solidarity of all the forms of life. But to all this the idea of actual descent was unnecessary. An actual material variation and transition from one stage to another seemed to it a wooden and gross expression of the evolution idea, an "all too childish and nebulous hypothesis" (Hegel).
All the important results of comparative morphology and physiology, which the modern supporters of the doctrine of descent so confidently utilise as arguments in its favour, would have been welcomed by those who held the original and general evolution idea, as a corroboration of their own standpoint. And as a matter of fact they all afford conclusive proofs of _evolution_; but not one of them, including even the fundamental biogenetic law and the inoculated chimpanzee, is decisive in regard to _descent_. This contention is sufficiently important to claim our attention for a little. Let us take the last example. Transfusion of blood between two species is possible, not necessarily because they are descended from one another or from a common root, but solely because of their systematic (ideal) relationship, that is to say because they are sufficiently near to one another and like one another in their physiological qualities and functions. If, a.s.suming descent, this h.o.m.ology were disturbed, and the systematic relationship done away with, for instance through saltatory evolution, the mere fact of descent would not bring the two species any nearer one another. Thus the case proves only systematic relationship, and only evolution. But as to the meaning of this systematic relationship, whether it can be "explained" by descent, whether it has existed from all eternity, or how it has arisen, the experiment does not inform us.
The same idea may be ill.u.s.trated in regard to Weismann"s "predicting."
This, too, is a proof of evolution, but not of descent. Exactly as Weismann predicted the striping of the hawk-moth caterpillars and the human _os centrale_, Goethe predicted the formation of the skull from modified vertebrae, and the premaxillary bone in man. In precisely the same way he "derived" the cavities in the human skull from those of the animal skull. This was quite in keeping with the manner and style of his G.o.ddess Nature and her creative transformations, raising the type of her creations from stage to stage, developing and expanding each new type from an earlier one, yet keeping the later a.n.a.logous to and recapitulative of the earlier, recording the earlier by means of vestigial and gradually dwindling parts.
But what has all this to do with descent? Even the "biogenetic law"
itself, especially if it were correct, would fit admirably into the frame of the pure evolution idea. For it is quite consistent with that idea to say that the higher type in the course of its development, especially in its embryonic stages, pa.s.ses through stages representative of the forms of life which are below it and precede it in the (ideal) genealogical tree.
Indeed, the older doctrine of evolution took account of this long ago.
"The same step-ladder which is exhibited by the whole animal kingdom, the steps of which are the different races and cla.s.ses, with at the one extreme the lowliest animals and at the other the highest, is exhibited also by every higher animal in its development, since from the moment of its origin until it has reached its full development it pa.s.ses through-both as regards internal and external organisation-the essentials of all the forms which become permanent for a lifetime in the animals lower than itself. The more perfect the animal is, the longer is the series of forms it pa.s.ses through."
So J. Fr. Meckel wrote in 1812 in his "Handbook of Pathological Anatomy,"
_with no thought of descent_. And the facts which led to the construction of the biogenetic law were discovered in no small measure by Aga.s.siz, who was an opponent of the doctrine of descent.(31)
But the advance from the doctrine of evolution to that of descent was imperatively prompted by a recognition of the fact that the earth is not from everlasting, and that the forms of life upon it are likewise not from everlasting, that, in fact, their several grades appear in an orderly ascending series. It is therefore simpler and more plausible to suppose that each higher step has arisen from the one before it, than to suppose that each has, so to speak, begun an evolution on its own account. A series of corroborative arguments might be adduced, and there is no doubt, as we have said before, that the transition from the general idea of evolution to that of descent will be fully accomplished. But it is plain that the special idea of descent contributes nothing essentially new on the subject.
It is an oft-repeated and self-evident statement, that it is in reality a matter of entire indifference whether man arose from the dust of the earth or from living matter already formed, or, let us say, from one of the higher vertebrates. The question still would be, how much or how little of any of them does he still retain, and how far does he differ from all?
Even if there be really descent, the difference may quite as well be so great-for instance, through saltatory development-that man, in spite of physical relationship, might belong to quite a new category far transcending all his ancestors in his intellectual characteristics, in his emotional and moral qualities. There is nothing against the a.s.sumption, and there is much to be said in its favour, that the last step from animal to man was such an immense one that it brought with it a freedom and richness of psychical life incomparable with anything that had gone before-as if life here realised itself for the first time in very truth, and made everything that previously had been a mere preliminary play.
On the other hand, even were there no descent but separate individual creation, man might, in virtue of his ideal relationship and evolution, appear nothing more than a stage relatively separate from those beneath him in evolution. It was not the doctrine of descent, it was the doctrine of evolution that first ranked man in a series with the rest of creation, and regarded him as the development of what is beneath him and leads up to him through a gradual sequence of stages. And his nearness, a.n.a.logy, or relationship to what is beneath him is in no way increased by descent, or rendered a whit more intimate or more disturbing.
The Problema Continui.
The problem of descent thus shows itself to be one which has neither isolated character nor special value. It is an accessory accompaniment of all the questions and problems which have been raised by, or are a.s.sociated with, the doctrine of evolution, which would have been in our midst without Darwin, which are made neither easier nor more difficult by zoological knowledge, and the difficulties of which, if solved, would solve at the same time any difficulties presented by descent. The following considerations will serve to make this clear. The most oppressive corollary of the doctrine of descent is undoubtedly that through it the human race seems to become lost in the infra-human, from which it cannot be separated by any hard and fast boundaries, or absolute lines of demarcation. But it is easy to see that this problem is in fact only a part of a larger problem, and that it can really be solved only through the larger one. Even if it were possible to do away with this unpleasing inference as regards the whole human race, so that it could be in some way separated off securely from the animal kingdom, the same fatality would remain in regard to each individual human being. For we have here to face the problem of individual development by easy transitions, the ascent from the animal to the human state, and the question: When is there really soul and spirit, when man and ego, when freedom and responsibility? But this is the same problem again, only written with smaller letters, the general _problema continui_ in the domain of life and mind. And the problem is very far-reaching. In all questions concerning mental health and disease, abnormalities or cases of arrest at an early stage of mental development, concerning the greater or less degree of endowment for intellectual, moral, and religious life, down to utter absence of capacity, and this in relation to individuals as well as races and peoples, and times; and again, concerning the gradual development of the ethical and religious consciousness in the long course of history, in its continuity and gradual transition from lower to higher forms: everywhere we meet this same _problema continui_. And our oppressive difficulty is bound up with this problem, and can be dispelled only by its solution, for the gist of the difficulty is nothing else than the _gradualness of human becoming_.
This is not the place for a thoroughgoing discussion of this _problema continui_. We can only call to mind here that the "evolution idea" has been the doctrine of the great philosophical systems from Aristotle to Leibnitz, and of the great German idealist philosophers, in whose school the religious interpretation of the world is at home. We may briefly emphasise the most important considerations to be kept in mind in forming a judgment as to gradual development.
1. To recognise anything as in course of evolving does not mean that we understand its "becoming." The true inwardness of "becoming" is hidden in the mystery of the transcendental.
2. The gradual origin of the highest and most perfect from the primitive in no way affects the specific character, the uniqueness and newness of the highest stage, when compared with its antecedents. For, close as each step is to the one below, and directly as it seems to arise out of it, each higher step has a minimum and differentia of newness (or at least an individual grouping of the elements of the old), which the preceding stage does not explain, or for which it is not a sufficient reason, but which emerges as new from the very heart of things.
3. Evolution does not diminish the absolute value of the perfect stage, which is incomparably greater than the value of the intermediate stages, it rather accentuates it. The stages from the half-developed acorn-shoot are not equivalent in value to the perfect tree; they are to it as means to an end, and are of minimal value compared with it.
4. All "descent" and "evolution," which, even in regard to the gradual development of physical organisation and its secrets, offer not so much an explanation as a clue, are still less sufficient in regard to the origin and growth of psychical capacity in general, and in relation to the awakening and autonomy of the mind in man, because the psychical and spiritual cannot be explained in terms of physiological processes, from either the quant.i.ty or the quality of nervous structure.
This problem, and the relation of the human spirit to the animal mind, will fall to be dealt with in Chapter XI. It is neither the right nor the duty of the religious conception of the world to inquire into and choose between the different forms of the idea of descent which we have met with.
If it has made itself master of the general evolution idea, then descent, even in its most gradual, continuous, monophyletic form, affects it not at all. It can then look on, perhaps not with joy, but certainly without anxiety, at Dubois" monkey-man and Friedenthal"s chimpanzee. On the other hand, it is obvious that a secret bond of sympathy will always unite it with the right wing of the theory of descent, with the champions of "halmatogenesis,"(32) heterogenesis,(33) kaleidoscopic readjustment, &c., because in all these the depth and wealth and the mystery of phenomena are more obviously recognisable. For the same reasons the religious outlook must always be interested in all protests against over-hastiness, against too great confidence in hypotheses, and against too rapid simplification and formulation. And it is not going beyond our province to place some reliance on the fact that there are increasing signs of revolt from the too great confidence hitherto shown in relation to the Theory of Descent.
The general frame of the theory will certainly never be broken, but the enclosed picture of natural evolution will be less plain and plausible, more complex and subtle, more full of points of interrogation and recognitions of the limits of our knowledge and the depths of things.
CHAPTER VI. DARWINISM IN THE STRICT SENSE.
It remains for us to consider what is essentially Darwinian in Darwinism, namely, the theory of natural selection as the determining factor in evolution. For, given the reality of evolution and descent, and that transformations from one form to another, from lower to higher, have really taken place, what was the guiding and impelling factor in evolution, what forced it forwards and upwards? It is here that the real problem of Darwinism begins. Only from this point onwards does the doctrine of evolution, which is not in itself necessarily committed to any theory of the factors, become definitely Darwinian or anti-Darwinian. And it is this problem that is mainly concerned in the discussions taking place to-day as to whether Darwin was right, or whether Darwinism as a hypothesis has not broken down.
The most characteristic feature of Darwin"s theory was "natural teleology," that is, the explanation of what is apparently full of purpose and plan in the world, purely as the necessary consequence of very simple conditions, without purpose or any striving after an aim. He sought to show that evolution and ascent can be realised through purely "natural"
causes, that this world of life, man included, must have come about, but not because it was intended so to do. In this sense, indeed, his doctrine is an attempt to do away with teleology. But in another sense it is so even more emphatically. The world, and especially the world of life, is undoubtedly full of what is _de facto_ purposive. The living organism, as a whole and in every one of its parts, is marvellously adapted to the end of performing its functions, maintaining its own life and reproducing.
Every single living being is a miracle of inexhaustible adaptations to an end. Whence came these? They, too, are products, unsought for, unintended, and yet necessary, and coming about "of themselves," that is without teleological or any supernatural guiding principles. To eliminate purpose and the purposive creating and guiding activity of transcendental principles from interpretations of nature, and to introduce purely naturalistic principles-"principles of chance," if we understand chance in this connection not as opposed to necessity, but to plan and purpose-this is the aim of the Darwinian theory. And it only becomes definitely anti-theological because it is anti-teleological.
The conclusions which Darwin arrived at as to the factors in the transformation of species, and in the production of "adaptations," have been in part supported by the specialists he influenced, in part strengthened, but in part modified and even reversed, so that a great crisis has come about in regard to Darwinism in the strict sense-a crisis which threatens to be fatal to it. We must here attempt to take a general survey of the state of the question and to define our own position.
Darwin"s interpretation is well known. It is the theory of the natural selection of the best adapted through the struggle for existence, which is of itself a natural selection, and results in the sifting out of particular forms and of higher forms. Darwin"s thinking follows the course that all anti-teleological thought has followed since the earliest times.
In bringing forth the forms of life, nature offers, without choice or aim or intention, a wealth of possibilities. The forms which happen to be best adapted to the surrounding conditions of life maintain themselves, and reproduce; the others perish, and are eliminated (survival of the fittest). Thus arises adaptation at first in the rough, but gradually in more and more minute detail. This adaptation, brought about by chance, gives _the impression_ of intelligent creative purpose.
In Darwin this fundamental mode of naturalistic interpretation took, under the influence of the social-economic theories of Malthus, the special form of natural selection by means of the struggle for existence, in a.s.sociation with the a.s.sumption of unlimited and fluctuating variability in the forms of life. All living beings have a tendency to increase in number without limit. But the means of subsistence and other conditions of existence do not increase at the same rate; they are relatively constant.
Thus compet.i.tion must come about. Any organism that is, by fortuitous variation, more favourably equipped than its fellows maintains itself and reproduces itself; the less favoured perish. For all things living are exposed to enemies, to untoward circ.u.mstances, and the like. Every individual favoured above its rivals persists, and can transmit to its descendants its own more favourable, more differentiated, more highly equipped character. Thus evolution is begun, and is forced on into the ever more diverse and ever "higher."
To Darwin this struggle for existence and this selection according to utility seemed, at any rate, the chief factor in progress. He did, indeed, make some concessions to the Lamarckian principle that new characters may be acquired by increased use, and to other "secondary" principles. But these are of small importance as compared with his main factor.
Differences of Opinion As To the Factors In Evolution.
The theory of natural selection in the struggle for existence rapidly gained wide acceptance, but from the first it was called in question from many sides. Bronn, who translated Darwin"s works into German, was and remained loyal to the idea of a "developmental law"-that there is within the organism an innate tendency towards self-differentiation and progress, thus a purely teleological principle.(34) Similarly, von Baer emphasised the idea of an endeavour to realise an aim; von Kolliker, that of "heterogenesis"; Nageli, that of an impulse towards perfection-all three thus recognising the theory of evolution, but dissenting from the view that the struggle for existence is the impelling factor and actual guide in the process. Very soon, in another direction, antagonism became p.r.o.nounced between the strictly Darwinian elements of the theory (the struggle for existence and its corollaries) and the accessory Lamarckian elements. Through these and other controversies the present state of the question has emerged.