Journal of the American Scientific Affiliation
Critique of Evolution
W. R. THOMPSON
JASA Vol 9, No 4, March 1960 pp. 2-10.
Thls Is the introduction to Charles Darwin's "Origin of Species" New York, E. P. Dutton & Co. Inc. 1956 and Is published with the permission of Dr. Thompson, Everyman's Library, and E. P. Dutton & Co., Inc.
When I was asked by the publishers of this new edition of The Origin of Species 1 to write an introduction replacing the one prepared a quarter of a century ago by the distinguished Darwinian, Sir Arthur Keith, I felt extremely hesitant to accept the invitation. I admire, as all biologists must, the immense scientific labours of Charles Darwin and his lifelong, singlehearted devotion to his theory of evolution. I agree that although, as he himself readily admitted, he did not invent the doctrine of organic evolution, or even the idea of natural selection, his arguments, and especially the arguments in The Origin of Species, convinced the world that he had discovered the true explanation of biological diversity, and had shown how the intricate adaptations of living things develop by a simple, inevitable process which even the most simple minded and unlearned can understand. But I am not satisfied that Darwin proved his point or that his influence in scientific and public thinking has been beneficial.
I therefore felt obliged to explain to the editors of Everyman's Library, that my introduction would be very different from that of Sir Arthur Keith, and that I could not content myself with mere variations on the hymn to Darwin and Darwinism that introduces so many text-books on biology and evolution, and might wel! be expected to precede a reprinting of the Origin. They raised no objection, so my main difficulty was removed. I am of course well aware that my views will be regarded by many biologists as heretical and reationary. However, I happen to believe that in science heresy is a virtue and reaction often a necessity, and that in no field of science are heresy and reaction more desirable than in evolutionary theory. I have written what I think should be written; but the responsibility of the editors of the library is not involved.
I have said that it was mainly The Origin of Species that converted the majority of men to the evolutionary doctrine. Sir Arthur Keith emphatically agreed. 'Not a book,' he said, 'has appeared to replace it; The Origin of Species is still the book which contains the most complete demonstration that the law of evolution is true.' But the more strongly we insist on this point, the more necessary it is to scrutinize the proofs given in the Origin. Of course, we may be induced to accept a statement that is true. by agreements that are fallacious or inadequate. Still, no one would seriously maintain that it is good to do the right thing for the wrong reasons. If arguments fail to resist analysis, assent should be withheld, and a wholesale conversion due to unsound argument must be regarded as deplorable.
For Sir Arthur Keith, Darwin as a writer may be classed among the 'small select group of great English men which holds Shakespeare.' The literary critics, apparently, did not agree with him. Though he has often been regarded as an obscure writer, Darwin usually expresses himself clearly enough. He was not interested in philosophical considerations or in the exact definition of the terms he used. In the final chapter of the first edition of Origin, where he recapitulates his arguments, the word evolution is not even mentioned; yet the proposition he is defending can easily be defined. This is, that all the organisms that exist or have exited have developed from a few extremely simple forms or from one alone, by a process of descent with modification. The mechanism of these transformations though infinitely complex in its detailed working, is very simple in principle. For reasons not fully understood organisms tend to vary slightly in their various characteristics. These variations must be called random in the sense that they haw no predestined relation to the well-being of the organism. Nevertheless since they occur continually in many directions, an individual in which a particular variation has occurred will have a slight advantage over its competitors in a particular environment. The advantage will be transmitted to its progeny in which, owing to variation, it will be manifested in different degrees, and thus there will occur through successive generations, a progressive adaptation to the environment from which the inadequately equipped competitors will disappear either through extinction or by adaptation to a different environment. We must, says Darwin, admit the truth of the following propositions: 'that gradations in the perfection of any organ or instinct, which we may consider, either do now exist or could have existed, each good of its kind -that all organs and instincts are, in ever so slight a degree, variable and, lastly, that there is a struggle for existence leading to the preservation of each profitable deviation of structure or instinct.' These truths being admitted, the theory of descent with modification through natural selection. must be accepted. This explanation has universal value. It enables us to under stand that every mental power and capacity has been a gradual but necessary acquirement and thus the origin and history of man become scientifically reprehensible. And as the past has been, so will the future. we may look with some confidence, says Darwin, 'to a secure future of equally inappreciable length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.'
The view that natural selection, leading to the survival of the fittest, in populations of individuals of varying characteristics and competing among themselves, has produced in the course of geological time gradual transformations leading from a simple primitive organ Ism to the highest forms of life, without the intervention of any directive agency or force, is thus the essence of the Darwinian position. Purposeless and undirected evolution, says J. S. Huxley, eventually produced, in man, a being capable of purpose and of directing evolutionary change. This, it appears to me, re mains the view of the most representative modern Dar winians. It is true that Darwin himself admitted a Lamarckian element, the effects of use and disuse, and Sir Arthur Keith defended him against those who accused him of relying exclusively on natural selection. But this. in the modern view, would be a virtue of Darwin's theory since the inheritance of acquired characters is now generally denied by biologists.
We must now examine the arguments in the 'demonstration that the law of evolution is true.'
Darwin's first argument, to which he devoted a great deal of labour, is that there is great variation among the individuals of many species. This variation is particularly evident among domesticated animals and plants. From these undeniable facts Darwin drew several conclusions. One was that species are not strictly immutable as biologists commonly maintained. The difference between the various type, of domesticated species is often much greater than that which exists be tween wild species, and even in these it is often extremely difficult to decide whether a particular form is a species or a variety. The great difference in the forms of domesticated species shows, on one hand, that variation can be stimulated by particular conditions and that the artificial selection made hy breeders has produced forms with extremely distinctive characteristics. The differences between the various species of violets or between the species of the hymenopterous genus Mesoleius, for example, are clearly far less striking than the differences between a pekinese and an Irish setter. or between a snow apple and a russet. Darwin points out that under certain conditions abnormal individuals are produced. and be maintains that it is im possible to draw a line between such monstrosities and the individuals regarded as normal. These con verging arguments indicate that what we call a species is just a transitional stage in a genealogical succession which cannot at any time be regarded as having a permanent definable essence or nature. There is therefore no inrinsic obstacle to unlimited evolution and the extrinsic conditions for it exist.
That natural selection directs the course of evolution
Darwin could not prove by all appeal to facts. However. he felt certain that all organisms tend to increase in geometrical ratio, that each lives by a struggle for its requirements at some period in its life and that among individuals differing even to a slight degree, the fittest must survive and transmit their characteristics to their offspring and, since these will continue to vary. natural selection will progressively improve the adaptations and equipment of each species. 'What checks the natural tendency of each species to increase in number,' said Darwin, 'is most obscure ... ' 'We know not exactly what the checks are even in one single instance.' He was able to show from factual examples that there is a great destruction of individuals in nature and to indicate some of the causes of this destruction: but he had little detailed evidence to offer concerning the action of natural selection.
Whether or not natural selection has produced the existing and past diversity of organic forms, this diversity exists, not only in space but in time. Such facts as the presence of different species of the same genus in different islands in the same area are consonant with the idea of descent with modification from a common ancestor as is the absence in isolated islands of organ isms without active powers of migration and the presence of others such as bats and birds, taxonomically related to those of mainland areas.
Other supporting arguments were advanced by Darwin: the slow change and apparent progression' of organic forms in the geological strata, the evidence of the existence in the past of a great variety of organisms now extinct; the similarity between the embryonic stages of organisms quite distinct in the adult condition; the existence of rudimentary organs; and the fact that a natural classification of organisms is possible, since this indicates real blood relationship and is therefore in a sense a mirror of the genealogical system hv which they arose.
I have tried to include in a necessarily brief summary the most important points in Darwin's argument and have not designedly attempted to weaken the presentation. If Darwin convinced the world that species had originated through evolution by natural selectio, it was, I think, on the basis of the arguments T have mentioned
But in a matter of this kind a great deal depends on the manner in which arguments are presented. Darwin considered that the doctrine of the origin of living forms by descent with modification, even if well foundded. would he unsatisfactory unless the causes at work were correctly identified, so his theory of modification by natural selection was, for him. of absolutely major importance. Since he had at the time the Origin was published no body of experimental evidence to sup port his theory. he fell back on speculative arguments The argumentation used by evolutionists. said de Quatrefages, makes the discussion of their ideas extremely difficult. Personal convictions, simple possibilities, are presented as if they were proofs, or at least valid arguments in favor of the theory. As an example de Quatrefages cited Darwin's explanation of the manner in which the titmouse might become transformed into the nutcracker, by the accumulation of small changes in structure and instinct owing to the effect of natural selection; and then proceeded to show that it is just as easy to transform the nutcracker into the titmouse. The demonstration can be modified without difficultv to fit any conceivable case. It is without scientific value, since it cannot be verified; but since the imagination has free rein, it is easy to convey the impression that a concrete example of real transmutation has been given. This is the more appealing because of the extreme fundamental simplicity of the Darwinian explanation. The reader may be completely ignorant of biological processes yet he feels that he really understands and in a sense dominates the machinery by which the marvelous variety of living forms has been produced.
This was certainly a major reason for the success of the Origin. Another is the elusive character of the Darwinian argument. Every characteristic of organisms is maintained in existence because it has survival value. But this value relates to the struggle for exis tence. Therefore we are not obliged to commit ourselves in regard to the meaning of difference between individuals or species since the possessor of a particular deification may be, in the race for life. moving up or falling behind. On the other hand. we can commit ourselves if we like, since it is impossible to disprove our statement. The plausibility of the argument eliminates the need for proof and its very nature gives. it a kind of immunity to disproof. Darwin did not show in the Origin that species had originated by natural selection, he merely showed, on the basis of certain facts and assumptions, how this might have happened, and as he had convinced himself he was able to convince others.
But the facts and interpretations on which Darwin relied have now ceased to convince. The long continued investigations on heredity and variation have under mined the Darwinian position. We now know that the variations determined by environmental changes the individual differences regarded by Darwin as the material on which natural selection acts are not hereditary. We can, by selection, sort out from a natural population a number of pure lines or genotypes, each possessing with respect to a given character its special curve of variability; but we cannot change this curve by selection within the genotype. For example, in a certain pure line of the house fly. those with the longest wings may conceivably have an advantage though I cannot see how this could be demonstrated. But we cannot, by choosing and mating these long winger flies, produce a progressive increase in the proportion of long winged flies, or a progressive increase in wing length.
It is true that some variations are hereditary. These are the so called mutations which do not develop gradually but appear suddenly and remain as they appeared. The varieties of domesticated plants and animals are the result of mutations. But such forms must be eliminated in nature, which would other wise present a spectacle entirely different from the reality. This is partly due to the fact that mutations are not adaptive. If we say that it is only by chance that they are useful. we are still speaking too leniently. In general, they are useless. detrimental, or lethal. Darwin himself did not think that the races of domesticated animals were capable of surviving in nature, hut the modern Darwinians are obliged to explain evolution as the result of mutations. If we minimize or at least limit the survival value of characters in general, we can agree that certain distinctive morphological dispositions may well be the the result of mutations. But the neo Darwinians hold firmly to the belief that every specific character has survival value. This to my mind puts them in a very awkward position.
To realize how unconvincing their position is, we have only to consider the fact of organic correlation. Strangely enough, though Darwin was evidently well acquainted with the work of Cuvier he pays practically no attention. in the Oriqiu, to Cuvier's principle of adaptive correlation. For him correlation is merely a concurrence of characters like 'the relation between blue eyes and deafness in cats, and the tortoise-shell colour with the female sex, the feathered felt and skin between the outer toes of pigeons, and the presence of more or less down on the young birds when first hatch ed. with the future color of their plumage; or, again, the relation between the hair and teeth in the naked Turkish dog.' Indeed Darwin's remarks suggest that he thinks of correlation as a material connection between malformations rather than as an adaptation. His modern disciples in general simply ignore the problem of correlation. However. to ignore it is easier than to solve it. As Emile Guyenot has said. mutations are powerless to explain the general adaptation which is the basis of organization. 'It is impossible to produce the world of life where the dominant note is functional organization. correlated variation and progression. from a series of random events.' The position therefore is that while the modern Darwinians have retained the essenials of Darwin's evolutionary machinery, to wit, natural selection, acting on random hereditary variations, their explanation. plausible in Darwin's day. is not plausible now.
It has been said that the substitution of particulate for blending inheritance removed what was a serious difficulty in Darwin's own position. The interference with progressive evolution resultiing from blending inheritance was certainly a weakness, in the argument of the Origin but, as I have said, particulate inheritance has introduced other difficulties.
An important point in Darwin's doctrine, as set out in the 0riqin was the conviction that evolution is a progressive process. We may look forward, he said, to a secure future of inappreciable length. 'And as natural selection works solely by and for the good of each being. all corporeal and mental endowments will tend to progress towards perfection.' The Victorians accepted this idea with enthusiasm. Here I need only to say that on this point Darwin was inconsistent since, in his view. natural selection acts not only by the survival of the fittest but also by the extermination of the less fit and may produce anatomical degradation as well as improvement.
That owing to the existence of different genotypes within a species and the somewhat different adaptive characters of these genotype~, samples of a widespread population taken at different points may be recognizably different in various ways. or a population of this kind spreading from a centre (as in the case of an introduced insect ) may develop local varieties sufficiently marked to be regarded as species by a taxonomist, may be freely acknowledged. Furthermore. when lye consider the development of a complex organism from the structurally simple germ cell. we must recognize that in this field, at least, evolution, in the classical sense, is a fact accessible to direct observation. But it is a far cry from these facts to the speculations of the Origin and the Victorian concept of evolution.
It is hardly necessary to dwell at length on all the minor arguments advanced by Darwin. These consist essentially in a translation of certain facts in terms (If evolutionary theory, or, in other words. on an historiical basis, If an organism possesses a structure having no assignable function. hut looking like a reduced specimen of a functional structure existing in some other form. it was regarded as a 'rudiment' whose existence is explicable only as a relic that has gradually degenerated in coming down from a remote ancestor, where it was well developed and functional.
It is clear that this supposition has no demonstrative value. It itself requires demonstration. Unless one adopts the Darwinian postulate that all characteristics have survival value. it is not necessary to assume that they have. or ever had. definite functions. Some so-called rudiments. such as the homologues of the mammary glands in man cannot. so far as an:' plausible evidence goes. have been inherited from an ancestor in which they were functional. Others. once believed to he useless, have definite functions. The existence in whales of transitory teeth and of small bones buried in the flesh,but corresponding to the pelvis, the femur. and the tibia. is commonly. regarded as a proof of their descent from ancestors of the tetrapod type with functional teeth; but in the first place some anatomists consider that these structures have an important role in the developmental process; ill the second place, we have no proof of a descent from ancestors in which these structures were more strongly developed; in the third place, it is clear that if they exist now, this is not primarily because they existed in the past, but because actual present causes now operate to produce them, What such cases like those of anatomical 'convergence' and general homology actually demonstrate is that there are large numbers of organisms. differing considerably in the de tails of structure but constructed on the same fundamental plan. However, this is no proof of descent from one original ancestor of this anatomical type. This itself requires proof. It may be said that unless we admit this, we must make the much more difficult supposition that many complex types originated independently. This, it wil! be remembered, was a point Darwin made against Lamarck. But I, for my part. do not see that I am obliged to express a view on such matters. Darwin himself considered that the idea of evolution is unsatisfactory unle-,s its mechanism can be explained. I agree, but since no one has explained to my satisfaction how evolution could happen I do not feel impelled to say that it has happened. I prefer to say that on this matter our information is inadequate.
Darwin suggested in the Oriqin that embryological development provide" evidence for evolution. He postulated that characteristics appear in the embryo at the stage in which they developed in the ancestor. so that new developments 1may be tacked on, so to speak, to a phase representing the ancestral development, since Darwin also held that the slight variations on which, in his view. evolution depends, 'generally appear at a not very early period of life.' This idea, elaborated by other workers. eventually became in the hands of Haeckcl the 'great biogenetic law,' according to which the ontogeny repeats the phylogeny, or. as propagandists have put it. the developing animal 'climbs up its family tree.'
A natural law can only he established as an induction from facts. Haekel was of course unable to do this. What he did was to arrange existing forms of animal li Ie in a series proceeding from the simple to the complex, interrelating imaginary entities where discontinuity existed and then giving the embryonic phases names corresponding to the stages in his so-callecl evolutionary series. Cases in which this parallelism did not exist were dealt with by the simple expedient of saying that the embryological development had been falsified. \\'hen the 'convergence' of embryos was not entirely satisfactory. Haeckel altered the illustrations of them to fit his theory. The alterations were slight hut significant. The 'biogenetic law' as a proof of evolution is valueless.
A more important argument in the opinion of Darwin himself was the possibility of classifying organisms.
All true classification, he said is genealogical. Community of descent 'is the hidden bond which naturalists
have been unconsciously seeking.'
The arrangement of the
of the groups within each class, 'in due subordination and relation to the other groups, must be strictly genealogical to be natural'. And again, 'the natural system is genealogical in its arrangement, like apedigree; but the degrees of modification which the different groups have undergone have to be expressed bv ranking them under so-called different genera, subfamilies, sections, orders, and classes.' What we call call the natural system of classification is a proof of evlution since it can only be explained as a result of evolution.
The plausibility of this argument is obvious. Yet it is not so convincing as it may appear at first sight. On the Darwinian theory, evolution is essentially undirected, being the result of natural selection, acting on small fortuitous variations. The argument specifically implies that nothing is exempt from this evolutionary process. Therefore, the last thing we should expect on Darwinian principles is the persistence of a few common fun damental structural plans. Yet this is what we find. The animal world, for example, can be divided into some ten great groups or phyla, all of which are not morphologically as coherent and clear-cut as we might wish for convenience in classification, but nevertheless are stable and definable entries from the taxonomic standpoint. All identifiable animals that ever have existed can be placed in these groups, Generally speaking, the subordinate groups are equally well defined, We can tell at a glance to what Order or Family a particular insect be longs. As I have already noted there is often controversy and uncertainty about the definitions of genera, species, and varieties; but taking the taxonomic system as a whole, it appears as an orderly arrangement of clear-cut entities which are clear-cut because they are separated by gaps. These gaps Darwin explained by the hypothesis that the intermediates are constantly eliminated by natural selection. I do not think we can be expected to accept his unproved supposition as an argument for Darwinism. But in any case it has no bearing on the persistence throughout geological time, in spite of the fortuitous variation and natural selec-tion, on the persistence of the fundamental anatomical plans exhibited by the great groups. Darwin insisted on several occasions that characteristics long inherited become stabilized and perhaps he considered that the persistence of morphological types can be explained inthis way. But without introducing considerations quite foreign to his system, we cannot explain why the anatomical type of the Echinoderm or the Insect continued.
Because all organisms we know are generated by other organisms, it is natural to interpret biological classification in terms of genealogy but not all the things that can be classified can be connected by generation. The arrangement of the chemical elements and their compounds is a true classification and so is the arrangement of geometric forms; yet no genealogical considerations are involved. Looking at the matter from this angle, we can easily see that in actual fact the system of biological classification is simply based on the char acteristics of organisms as they are here and now. The basis of these characteristics here and now is the physico-chemical constitution. If we wish to erect a genealogical classification we cannot do so with a collection of abstractions drawn from our arrangement of existing organisms we must discover through what forms the existing organisms have actually descended. If these historical facts cannot be ascertained, then it is useless to seek for substitutes, and from the fact that a classication is possible we certainly cannot infer that it is genealogical and is in any sense a proof of evolution.
Evolution, if it has occurred, can in a rather loose sense be called a historical process; and therefore to show that it has occurred historical evidence is required, History in the strict sense is dependent on human testirnony, Since this is not available with respect to the development of the world of life we must be satisfied with something less satisfactory, The only evidence available is that provided by the fossils. It has been pointed out by both supporters and opponents of the chronological succession of certain organisms, this is not proof of descent. This may seem like a quibble, If we put a pair of houseflies in a cage and let them breed, we do not doubt that the live flies we find there in a month's time are the descendants of the original pair Similarly, if in an apparently undisturbed geological formation we find snail shells at an upper level very similar to those at a lower level, we may reasonably con elude that there is some genealogical connection between the two groups, though we cannot trace the des cent from individual to individual as is required in a true family tree. Therefore, if we found in the geological strata a series of fossils showing a gradual transi tion from simple to complex forms, and could be sure that they correspond to a true time-sequence, then we should be inclined to feel that Darwinian evolution has occured, even though its mechanism remained unknown. This is certainly what Darwin would have liked to report but of course he was unable to do so. What the available data indicated was a remarkable absence of the many intermediate forms required by the theory; the absence of the primitive types that should have existed in the strata regarded as the most ancient; and the sudden appearance of the principle taxonomic groups. Against these difficulties he could only suggest that the geological record is imperfect, but that if it had been perfect it would have provided evidence for his views.
It is clear therefore that the palaeontological evidence at his disposal, since it had not led competent naturalists acquainted with it to a belief in evolution, could only justify a suspense of judgment. The cond tion of fossil material is, of course, unsatisfactory since soft tissues usually disappear, leaving only skeletal structures, frequently much distorted. The fossil insects of the group with which I am best acquainted cannot be accurately determined, even to genera. It is evident that many organisms now extinct existed in the past, but we can never know them as we know living forms. The chronological succession of the fossils is also open to doubt, for it appears, generally speaking, that the age of the rocks is not determinecl by their intrinsic characteristics hut by the fossils they contain; while the suc cession of the fossils is determined by the succession of the strata. It was thought also that the fossils should appear in a certain order, corresponding roughly to the stages in embryological development. In fact the strata, and therefore the fossils they contain, do not always occur in the accepted order. I n some areas of the world for example, the Cambrian strata, which are regarded as the oldest fossiliferous formations, rest on the Cretaceous which are regarded as relatively recent; in oth er, Cretaceous or Tertiary beds appear, instead of the Cambrian. on the granite. Sometimes the character of the deposits would lead to the belief that they were chronologically continuous since they can be separated only by the fossils they contain. Various hypotheses have been proposed to explain these departures from ac cepted theory, and though they are often the subject of controversy among geologists 1 do not suggest that the problems to which they relate are insoluble.
On the other hand, it does appear to me, in the first place, that Darwin in the Origin was not able to pro duce palaeontological evidence sufficient to prove his views hut that the evidence he did produce was adverse to thorn : and I may note that the position is not notably different to-day. The modern Darwinian palaeontolo gists are ohliged, just like their predecessors and like Darwin, to water down the facts with subsidiary hypo theses which, however plausible, are in the nature of things unverifiable.
It has been said that though we do not find in the geological deposits the intermediates required by Darwinian theory, some very striking intermediates have heen found of which the classical oft-cited example is Arcliacoptervx, To me, however, it appears that since the geological strata probably represent environmental conditions very different from those of the present, col lections made in them may be regarded something like those made on the continent of Europe or in the trop ics, with respect to the fauna and flora of the British Isles. /\5 the range of our collections extends, so we in variably enrich our representation of various groups, and this necessarily and inevitably entails the appearance of intermediate between the forms in the collection from the restricted area in which we started. The recognition of this fact, with respect to the collections of organisms existing here and now, does not neces sarily commit us to any particular view of the origin of species; and the same thing is true of the collection of fossil material.
The Oriqin of Species converted the majority of its readers to a belief in Darwinian evolution. We must now ask whether this was an unadulterated benefit to biology and to mankind. Sir Arthur Keith, as we have seen, had no doubts about this point. Some of the Darwinian propagandists were even more positive.
\Vriting in his Anthropogeny of the evolutionary con troversy, Haeckel asserted, that in this intellectual bat tle, which excites all the thinking sections of humanity, and prepares for the future a truly humane society, we ,ee 011 one side, uncler the splendid banner of science, the liberation of the mind, truth, reason, civilization, development, and progress. In the other camp are ranged, under the banner of the hierarchy, intellectual servitude, error, irrationality, barbarous ways of life, superstition, and decadence. Quite recently an evolutionary propagandist has said, that without the evolu tionary doctrine, biology, except in certain restricted fields, becomes unintelligible.
I find myself unable to agree with these views. I do not contest the fact that the advent of the evolutionary idea. due mainly to the Origin, very greatly stimulated biological research. But it appears to me that owing precisely to the nature of the stimulus, a great deal of this work was directed into unprofitable channels or devoted to the pursuit of will-of-the-wisps, I am not the only biologist of this opinion. Darwin's conviction that evolution is the result of natural selection, acting on small foruitous variations, says Guyenot, was to delay the progress of investigations on evolution by half a century. Really fruitful researches on heredity did not begin until the rediscovery in 1900 of the fundamental work of Mendel, published in 1865 and owing nothing to the work of Darwin. In his great work Growth and Form, D'Arcy Thompson remarked on the stult fying effect of Darwinian theory. 'So long and so far as "fortuitous variation" and the "survival of the fittest" remain engrained as fundamental and satis factory hypotheses in the philosophy of hiology, so long will these "satisfactory and specious causes" tend to stav "severe and diligent inquiry," "to the great ar rest and prejudice of· future discovery." , Much time was wasted in the production of unverifiable family trees. For example, by plausible but unconvincing ar guments zoologists have 'demonstrated' the descent of the Vertehrates from almost every group of the In vertebrates. During the thirty years from 1870 to 1900, there was an immense concentration of effort on em bryology, inspired by the 'biogenetic law.' Here again the main objective was the tracing of ancestries. The attempt of his to explain development in terms of ac tual physical causes was rejected with contempt by au thors like Haeckel. '\Ve have better things to do in embryology,' said one of them, 'than to discuss tensions of germinal layers and similar questions, since all ex planations must of necessity be of a phylogenetic na ture.' Gradually it was realized that the obj ective was unattainable. Embryology then ceased to be fashion able. Taxonomists also followed the trend, construct ing hypothetical ancestors for their groups and ex plaining the derivation of existing forms from these imaginary entities. I do not of course deny that a great amount of valuable information was gathered in these studies, but I think it could have been obtained more effectively on a purely objective basis. My impression is, also, that though it was unproductive from the Darwinian standpoint, this was not usually admitted. The deficiencies of the data were patched up with hypothe ses, and the reader is left with the feeling that if the data do not support the theory they really ought to.
A long-enduring and regrettable effect of the success of the Origin was the addiction of biologists to un verifiable speculation. 'Explanations' of the origin of structures, instincts, and mental aptitudes of all kinds, in terms of Darwinian principles, marked with the Dar winian plausibility but hopelessly unverifiable, poured out from every research centre. The speculations on the origin and significance of the resemblances between animals, or between animals and their environment and of the striking colour patterns they often exhibit, constitute one of the best-known examples. In the ar ticle on 'Mimicry' in the 14th edition of the Encyclo pedia Britannica we find a remarkable explanation of the form of tropical insect belonging to the group of the 'lantern-flies.' The head of this insect, which is not very large, resembles, in miniature, the head of an alli gator, being prolonged into a snout at the base of which is a protuberance resembling an eye, while along the side are formations resembling minute teeth. Curious though the resemblance is, it is obviously a mere coin cidence. The insect as a whole does not look anything like an alligator. However, for the Darwinian author of the article we have here an example of the develop ment of protective resemblance by natural selection. The similarity of the head of the insect to the head of an alligator is a protection against monkeys. The monkey does not actually mistake the insect for an alligator but the sight of its head recalls to him the occasion on w h i chan alligator almost seized him when he was drinking from a stream. Such is the effect of Darwinian fantasy on biological thinking.
The success of Darwinism was accompanied by a decline in scientific integrity. This is already evident in the reckless statements of Haeckel and in the shifting, devious, and histrionic argumentation of T. H. Huxley.
A striking example, which has only recently come to light, is the alteration of the Piltdown skull so that it could be used as evidence for the descent of man from the apes; but even before this a similar instance of tinkering with evidence was finally revealed by the discoverer of Pithecanthropus, who admitted, many years after his sensational report, that he had found in the same deposits bones that are definitely human. Though these facts are now well known, a work pub lished in 1943 still accepts the diagnosis of Pithecan thropus given by Dubois, as a creature with a femur of human form permitting an erect posture. Not long ago (1947), an exhibit in London, designed for pub lic instruction. presented human development in such a way as to insinuate the truth of the 'biogenetic law'; and in the same exhibit were problematic reconstruc tions indicating the descent of man and including the Pilt down type.
As we know, there is a great divergence of opinion among biologists, not only about the causes of evolu tion but even about the actual process. This divergence exists because the evidence is unsatisfactory and does not permit any certain conclusion. It is therefore right and proper to draw the attention of the non-scientific public to the disagreements about evolution. But some recent remarks of evolutionists show that they think this unreasonable. This situation, where scientific men rally to the defence of a doctrine they are unable to de fine scientifically, much less demonstrate with scienti fic rigour, attempting to maintain its credit with the public by the suppression of criticism and the elimina tion of difficulties, is abnormal and undesirable in science.
It is difficult to assess the effect of the Oriqin on the public mentality. It must be considered in conjunction with Darwins' later work: The Descent of lVI an and the writings of the supporters of Darwin in several coun tries. However. Sir Arthur Keith said that Darwin himself had done more than anyone to lift 'the pall of superstition' from mankind and, in another place, that Darwinism is a 'basal doctrine in the rationalistic li turgy.' These remarks suggest that in his opinion the decline of belief in the supernatural. and probably the decline of Christinity. is largely due to the influence of Darwin. I think there is much to be said for this view. It is true that in the Origin, Darwin speaks of life 'having been originally breathed into a few forms or into one'; and refers to a Creator. Furthermore, he objected to the spontaneous generations for which Lamarck argued. But I think this objection was merely to an idea that would haw made his own theory less comprehensively explanatory.
Although the Origin contains no direct attack on the Christian concept of the universe. it is, on a number of crucial points, opposed to this concept. The biblical ac count of the creation of living things can be, and often has been interpreted ill a manner more or less compatible with the doctrine of evolution. Propagandists like T. H. Huxley, however, made every effort tu minimize this possibility, and to prove that Christian orthodoxy im plies a literal interpretation of Genesis which is irre concilable with the evolutionary idea. Darwin himself though he once held some rather vaguely Christian views, abandoned them quite rapidly anrl soon ceased to believe in the Christian revelation.
The doctrine of evolution by natural selection as Darwin formulated. and as his followers still explain it, has a strong anti-religious flavour. This is due to the fact that the intricate adaptations and co-ordinations we see in living things, naturally evoking the idea of finality and design and. therefore, of an intelligent providence, are explained. with what seems to be a rigorous argument. as the result of chance. It may be said, and the orthodox theologians indeed hold, that God controls and guides even the events due to chance; but this proposition the Darwinians emphati cally reject. and it is clear that in the Oriqi« evolution is presented as an essentially undirected process. For the majority of its readers, therefore, the Oriyin effectively disipated the evidence of providential control. It might be said that this was their own fault. n everthe les the failure of Darwin and his successors to attempt an equitable assessment of the religious issues at stake indicates a regrettable obtuseness and lack of responsibility. Furthermore. on the pure philosophical plane, the Darwinian doctrine of evolution involves some diffi culties which Darwin and Huxley were unable to ap preciate. Between the organism that simply lives, the organism that lives and feels. and the organism that lives, feels, and reasons, there are, in the opinion of respectable philosophers, abrupt transitions corresponding to an ascent in the scale of being, and they hold that the agencies of the material world cannot produce trunsitions of this kind. I shall not attempt to discuss this difficult question here. Nevertheless it is clear that the view just mentioned has been that of mankind in general. That plants, animals, and man can be distin guished because they are radically different is the commen-sense conviction, or was, at least until the time of Darwin. Biologists still agree on the separation of plants and animals. but the idea that man and animals differ only in degree is now so general among them, that even psychologists no longer attempt to use words like 'reason'' or 'intelligence' in all exact sense.
This general tendency to eliminate, by means of unverifiable speculations, the limits of the categories Nature presents to us, is the inheritance of biology from The Oriqin of Species. To establish the continuity re quired by theory, historical arguments are invoked, even though historical evidence is lacking. Thus are engendered those fragile towers of hypothesis based on hypothesis, there fact and fiction intermingle in an inextricable confusion. That these constructions correspond to a natural appetite, there can be no doubt. It is certain also that in the Origin Darwin established what may he called the classical method of satisfying this appetite.We are beginning to realize now that the method is unsound and the satisfaction illusory. But to under stand our own thinking, to see what fallacies we must eradicate in order to establish general biology on a scientific basis, we can still return with profit to the source-book which is The Origin of Species
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