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DARWIN'S CENTURY -- EVOLUTION AND THE MEN WHO DISCOVERED IT |
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Chapter IX: Darwin and the Physicists
I. Kelvin and Residual Heat We have seen, in our earlier discussion of Sir Charles Lyell and the uniformitarian hypothesis in geology, what a vast reversal in human conceptions of the age of the earth went on in the Christian world in the earlier part of the nineteenth century. We also observed in the course of that survey what visions of limitless time, "millions of ages," as Erasmus Darwin somewhere remarks, were a necessary preliminary premise before a satisfactory theory of evolution could be entertained. The slow organic change postulated by both Lamarck and Darwin demanded time far beyond anything conceived in the Mosaic account of Creation. The existence of time of such magnitude, beginning with the labors of Hutton, Playfair, and others, was pretty well demonstrated to the satisfaction of all objectively minded scholars by the mid-century. It formed, in fact, part of the necessary groundwork of the Origin of Species. Strangely enough, however, within six years after the publication of that work an attack on the conception of unlimited geological time had been launched with such vigor that, by the end of the century, it was still one of two leading arguments entertained by many naturalists as casting doubt upon the principle of natural selection. It had shaken the confidence of Darwin himself, forced Huxley into a defense characterized more by sophistry than scientific objectivity, and placed geology in general in the position of an errant schoolboy before his masters. The attack had been launched by Lord Kelvin, contended by many historians of science to be the outstanding physicist of the nineteenth century. Today there is a tendency in some quarters to regard the physical sciences as superior in reliability to those in which precise mathematical adeptness has not been achieved. Without wishing to challenge this point of view, it may still be worth a chastening thought that, in this long controversy extending well over half a century, the physicists made extended use of mathematical techniques and still were hopelessly and, it must be added, arrogantly wrong. By contrast, the geologists who appeared to their physicist colleagues as bumbling amateurs expressing themselves only in vague hunches, and who could produce few arguments that the great Kelvin would deign to notice or to answer, happen to have been remarkably right. But in those days of the seventies things were going badly for Darwin and his followers. If fortuitous variations were the source of the great diversity of planetary life, then time was of the essence of the matter. A contraction in the time scale, therefore, must inevitably force biologists to a rejection of fortuitous variation in favor of some type of more rapid orthogenetic and therefore possibly teleologically directed change. Whether Lord Kelvin and his Scotch associate, Peter Tait, saw this inevitable consequence of their thought one cannot but wonder, since they were devoutly religious men. At any rate, they pressed their advantage hard. In the words of Sir Archibald Geikie, "the physicists have been insatiable and inexorable. As remorseless as Lear's daughters, they have cut down their grant of years by successive slices, until some of them have brought the number to something less than ten millions." [1] Today when the antiquity of life on the planet is beginning to be conservatively estimated at close to three billion years it can readily be seen that calculations as low as ten to thirty million years for the elapsed time since life on earth would have been possible placed an enormous strain on the Darwinian theory. It became, in other words, increasingly difficult to see how an evolutionary theory operating primarily on the basis of fortuitous mutations occurring at lengthy intervals, and only then being selected by the winnowing process of natural selection, could possibly account for the diversity of existing organic life in the short interval of a few million years. It can be observed from Darwin's letters that this new development in physics gravely troubled him. He refers to Lord Kelvin as an "odious spectre,'' [2] and in a letter to an unknown correspondent in the collections of the American Philosophical Society he writes: "Notwithstanding your excellent remarks on the work which can be effected within a million years, I am greatly troubled at the short duration of the world according to Sir W. Thomson [Lord Kelvin] for I require for my theoretical views a very long period before the Cambrian formation." [3] Let us now investigate, from the historical standpoint, how this peculiar situation had come about in the short time since Darwin had published The Origin of Species. By the last decade of the nineteenth century Lord Salisbury, in his Presidential Address before the British Association for the Advancement of Science, was able to bring forward as the two strongest objections to the Darwinian hypothesis the Insufficiency of time for evolution by such a method and, second, the impossibility of demonstrating natural selection in detail. [4] Though not at first glance obvious, the two points are actually interlinked in some degree as we will later be able to observe. Though the nature of our major subject will not permit a lengthy analysis of the developments leading to Lord Kelvin's position, we may note in passing that they were the inevitable outcome of the cosmic evolutionism of the late eighteenth century. Temperatures taken in deep mines indicated an increase of heat as one went downward, and these observations were occasionally dwelt upon in scientific papers during the early nineteenth century. What began to be regarded as the secular cooling of the earth, its dissipation of heat from its original molten condition into the freezing space around it, began to occupy attention. The geologist George Greenough, for example, in his Anniversary Address before the Geological Society of London in 1834, remarked that "it appears certain that the surface of our planet has become cooler and cooler, from the period when organic life commenced to the Tertiary epoch." The growing recognition in geological studies of the second law of thermodynamics would thus inevitably bring into question the :Implied eternities of the early uniformitarians. When to this problem of the residual heat of the earth was added the question of the age of the sun's heat and its influence upon the life of the earth, it was inevitable that there should be a demand for geological reform. "British popular geology," insisted Lord Kelvin, "is in direct opposition to the principles of Natural Philosophy." "I take the sun much to heart," groaned Darwin to Lyell in 1868. It is interesting to note that although time in quantity had been implied by many solar observations there had been, prior to Kelvin, comparatively few attempts to relate astronomical to geological problems. The uniformitarian geologists, in fact, had in their earlier phase "discerned neither a beginning nor an end: Darwin, in the first edition of the Origin, had ventured that "in all probability a far longer period than 300,000,000 years had elapsed since the latter part of the secondary period." [5] Even today, with radioactive methods of checking time in the rocks, this figure would be regarded as excessive. The later editions of the Origin do not carry it. One may suspect that, just as today the study of man in the Pleistocene has greatly intensified our efforts to define, subdivide, and date this epoch, so the emergence of the evolutionary theory after 1859 as a leading aspect of biological thought enormously enhanced the human effort to date the past. The past had no longer the static or cyclic quality of the classical Greco-Roman conception, nor, by contrast, the six-thousand-year ephemeral duration accorded it by orthodox Christians. Change had entered the world; time was debatable and open to scientific examination. Lord Kelvin had thrown down a direct challenge to the geologists and, by indirection, to the evolutionists themselves. At the close of the century the two antagonistic camps would still be in existence. A collected bibliography of the subject through the period 1862 to 1902 would be enormous. What concerns us here, however, is the effect which Kelvin and his colleagues in physics had upon both the geologists and biologists. It was impossible to ignore Kelvin. Given the physics of the time there was no way of escaping him. Many geologists capitulated and revised their calculations of the earth's antiquity downward. Biologists, trapped in a more difficult impasse, tried to find their way out through various ancillary hypotheses. Three papers written by Lord Kelvin and dating back to the early sixties may serve to indicate the major points which he was to emphasize, with elaboration of detail, until the close of the century. "On the Age of the Sun's Heat," written for Macmillan's Magazine, [6] expounds the view, also supported by Helmholtz and others, that the sun is an incandescent liquid mass which is dissipating its energy at a rapid pace. Lord Kelvin could see no way in which this loss of radiant energy could be compensated for by other mechanisms. Therefore, argued Kelvin, the sun's future life is limited, and, in its not too lengthy past, it must at one time have been sensibly hotter than at present. "As for the future; said Kelvin in a similar paper which he delivered before the British Association in 1861, "we may say with ... certainty that inhabitants of the earth cannot continue to enjoy the light and heat essential to their life for many million years longer, unless [he added with unconscious prophecy] new sources now unknown to us, are prepared in the great storehouse of Creation." [7] Atomic energy was not, of course, discovered until the twentieth century, but it was already warming the earth that Kelvin gazed upon so gloomily. Ten per cent less light and heat would destroy us, we know now, and ten per cent more heat would boil us alive. Throughout the whole great range of geological time, modem science now tells us, our sun can have changed only insensibly at best from its original state. [8] Otherwise there would have been no continuity of life upon earth. In 1865 Kelvin turned directly to the geologists with a paper whose very title was a forthright challenge: "The Doctrine of Uniformity in Geology Briefly Refuted," [9] which he read before the Royal Society of Edinburgh. It is an attempt to demonstrate mathematically, in terms of heat loss, that the earth's crust cannot have maintained its stability over such an enormous time range as that demanded by the theories of the uniformitarian geologists and the evolutionary biologists who relied upon them. Later, in 1869, Thomas Huxley attempted a counter-blow which did not prove particularly convincing. Essentially, he attempted to evade the issue by the nonchalant pose that "Biology takes her time from Geology. The only reason we have for believing in the slow rate of the change in living forms is the fact that they persist through a series of deposits which geology informs us have taken a long while to make. If the geological clock is wrong all the naturalist will have to do is to modify his notions of the rapidity of change accordingly." [10] (Italics mine. L.E.) On an earlier page I have spoken of this as sophistry. At best it was a mere delaying action. For if evolutionary biology relied for change upon infinitesimal variations acted upon by natural selection through long time periods, it was difficult to see how the process could be "speeded up" to accord with the new facts of geology unless Huxley had a new theory to propose in place of natural selection. Huxley proposed nothing new. "It is not obvious," he went on, "that we shall have to alter or reform our ways...." [11] With his old proud gladiatorial skill he referred to himself as a counsel who contrives to gain his cause "by force of mother-wit...." [12] This was not, however, a struggle which debating skill alone could win. Though we know now that Lord Kelvin was wrong, he was, paradoxically, right in terms of nineteenth-century physics. Grimly he ignored the elusive footwork of Huxley. "A correction of this kind," he observed to the Geological Society of Glasgow, "cannot be said to be unimportant in reference to biological speculation. The limitation of geological periods imposed by physical science cannot, of course, disprove the hypothesis of transmutation of species; but it does seem sufficient to disprove the doctrine that transmutation has taken place through 'descent with modification by natural selection.'" [13] (Italics mine. L.E.) Squirm as he might, Huxley could not totally evade that point. It is no wonder that Darwin, beset simultaneously by both the Jenkin and Kelvin nightmares, began to fall back toward the familiar landmarks of his youth, toward the "inherited effects of habit," toward that shadowy biological borderland haunted by Lamarck and the ghost of his grandfather. In this instance the swashbuckling of Huxley did not impress him. Painfully and doubtfully he wrote to Wallace in 1871, "I have not as yet been able to digest the fundamental notion of the shortened age of the sun and earth." [14] Kelvin pressed his advantage relentlessly. "We find at every turn something to show ... the utter futility of [Darwin's] philosophy," [15] he said in 1873. By 1893 he was willing to go along with the American Clarence King's estimate of the age of the earth as around twenty-four million years. "I am not led to differ much," [16] said Kelvin. Today these twenty-million-year estimates of the earth's antiquity would take us only into the upper reaches of the Age of Mammals. This will give us some idea of the contracted time span that had been forced upon a science used to reveling in time vistas of which Hutton had spoken long ago as having "no vestige of a beginning, no prospect of an end." The great rout was on at last. The science of geology had ceased to be what it was to the early uniformitarians, "the science of infinite time." Most of the geologists, though occasionally hedging, grumbling, and not averse to claiming a few extra million years for themselves, fell in line reluctantly with the physicists. Sollas confessed that "so far as I can at present see, the lapse of time since the beginning of the Cambrian system is probably less than seventeen millions of years...." [17] By 1900 he was aware that "eminent biologists" besides himself were willing to settle for twenty-six million years as satisfying the needs of evolutionists. [18] Charles Walcott conceded geologic lime could be measured by tens of millions of years. [19] Falling in with Huxley's position he remarks evasively, "I have not referred to the rate of development of life, as that is virtually controlled by conditions of environment." Sir Archibald Geikie, although protesting "a flaw in a line of argument which tends to results so entirely at variance with the strong evidence for a higher antiquity," was willing, nevertheless, to settle for 100 million years. This figure, he modestly maintained, would content the geologists whose errors he admitted. [20] II. The Biological Retreat The biologists, confronted in this manner by the defection of the geologists, began to grope for feasible solutions. This groping is important to observe because it is part of the confused intellectual climate out of which emerged a momentary anti-Darwinian trend and which, at the same time, contributed to the stimulation of researches leading toward the rediscovery of Gregor Mendel. Darwin died before the new trend culminated. He admitted in the sixth edition of the Origin that the objection to natural selection raised by Lord Kelvin was a very formidable one. A close examination of the last edition of the Origin reveals that in attempting on scattered pages to meet the objections being launched against his theory the much-labored-upon volume had become contradictory. In Chapter XI, surviving from earlier editions, we read: "There is some reason to believe that organisms high in the scale, change more quickly than those that are low." [21] Darwin dwells on the "slow and scarcely sensible mutations of specific forms." [22] Then, as we turn to another section, we suddenly discover a converse statement apparently inserted as a device to evade Lord Kelvin's mathematics. We perceive with mild astonishment that "the world at a very early period was subjected to more rapid and violent changes in its physical conditions than those now occurring; and such changes would have tended to induce changes at a corresponding rate in the organisms which then existed." [23] (Italics mine. L.E.) The last repairs to the Origin reveal, both in connection with Lord Kelvin and Jenkin, how very shaky Darwin's theoretical structure had become. His gracious ability to compromise had produced some striking inconsistencies. His book was already a classic, however, and these deviations for the most part passed unnoticed even by his enemies. The number of improvisations which had had to be marshaled to the assistance of natural selection remind one at times of the difficulties which Lamarck tried to meet by additional hypotheses. Wallace had suggested that periods when the earth's orbit was less eccentric would give an impression of greater stability so far as the living world was concerned. Changes in the earth's orbit, on the other band, would, he contended, stimulate climatic change and thus speed the process of evolution. This, he thought, would account for a more rapid rate of organic change and enable us to fit the main events of evolution within a shorter time scale. [24] Adam Sedgwick, a younger relative of Darwin's old geology professor, proposed a theory that selection tends to diminish the Variability of species. Therefore, he reasoned, "variation must have been much greater in the past than now.... This view, if it can be established, is of the utmost importance to our theoretical conception of evolution, because it enables us to bring our requirements as to time within the limits granted by the physicists." [25] "That variation," Sedgwick goes on to say, "was much greater near the dawn of life than it is now, and heredity a correspondingly less important phenomenon, is a deduction from the selection theory." [26] Sedgwick here seems to have developed another version of the Darwinian argument that evolution proceeded rapidly at the dawn of life. Others, like Lloyd Morgan, found solace in repeating Huxley's argument that time is the business of the geologist and that the biologist can adjust accordingly. No Darwinist could be long happy with this argument, however, which, as Kelvin had warned, left the notion of fortuitous mutation and selection in a most dubious position. Nor, for that matter, were the geologists entirely happy. They were willing to admit that a false analogy had, in the past, "been set up between the boundless infinity of space and the vast immensity of past time," [27] but the voluminous records of past life and the time ratios founded upon sedimentation did not fit easily into the strait jacket of the physicists. The geologists, shrewdly observed G. K. Gilbert, were "making as earnest an effort for reconciliation as had been made a generation earlier to adjust the elements of the Hebrew cosmogony to the facts of geology." [28] We might add that just as the earlier attempt had proved hopeless so, in the end, would this similar effort. Geological time, as foreseen by the eloquent Huxley, sprang irresistibly out of the facts. It was, as he had said, like the djin from the jar which the fisherman had opened. It was "vaporous, shifting, and undefinable, but unmistakably gigantic." In the end, for all their striving, the physicists would be unable to coax the monster back into the bottle. To this day it is continuing to expand. III. De Vries and Saltatory Evolution We have previously had occasion to examine the way in which the blending idea of inheritance held in Darwin's time led the author of the Origin into difficulties with the mathematically inclined engineer Fleeming Jenkin. We have, furthermore, noted Lord Salisbury's stricture at the end of the century that, along with the problem of time, which we have just surveyed, the second point which left the status of Darwinian evolution inconclusive was the inability to demonstrate natural selection in detail. All in all, then, we may observe that Jenkin, and Lord Kelvin, along with a host of followers had forced Darwin, before his death, into an awkward retreat which mars in some degree the final edition of the Origin. As C. D. Darlington has ironically expressed it: "He panicked and ran straight into the opposite camp....Lamarck became a posthumous Darwinian." [29] Within two years of Darwin's death a letter to Wallace insists: "It is Impossible to urge too often that the selection from a single varying individual or of a single varying organ will not suffice." [30] Even his old colleague Wallace was constrained to remark in a letter to Professor Meldola fifteen years after Darwin's death that his addiction to notions of the hereditary effects of climate, food, etc., upon the individual "led to much obscurity and fallacy in his arguments, here and there." [31] It is unnecessary to pursue further the inconsistencies of an outstanding and basically courageous thinker. As we have seen in a previous chapter, Darwin was essentially a transitional figure standing between the eighteenth century and the modem world. He had never entirely escaped certain of the Lamarckian ideas of his youth, whether they came by way of Lyell, or independently from his grandfather, or, as is more likely, from both. As a consequence it Is not surprising that in a time of stress he grew doubtful that natural selection contained the full answer to the sallies of his critics. He fell back, therefore, toward ideas he had never totally repudiated but which, in the first edition of the Origin, had been allowed to remain in the background, masked, in a sense, while the major emphasis had been placed upon natural selection. The inheritance of habit, incidentally, is indirectly an excellent device for speeding up evolution in a world where time is short. Darwin made use of it in The Descent of Man. It is not Darwin but the younger generation of evolutionists who must now concern us. By and large they had accepted the evolutionary point of view, but they were oppressed by the confused and incoherent situation which they had inherited from the dead, master. The relative value of natural selection against the Lamarckian approach was being reweighed. The nature of heredity was under debate and the rate of organic change was, as we have already observed, a matter of great concern. Weismann had overthrown Herbert Spencer's support of the Lamarckian position. In spite of Darwin's past hesitations, change appeared to be, not the result of climatic stimulation upon the germ cells, but the product of some imponderable chance, or so it seemed, emanating from those same germ cells. This development, more or less divorcing mutations from environmental influence, made even more impossible the attempt to assume rapid mutative change accommodating its emergence entirely to physical and climatic episodes upon the planet. The latter factors might in some degree select, but could not stimulate, the appearance of new variations. It is now clear that evolutionary science in the last decade of the nineteenth century was drastically in need of a new approach. The old catastrophic cosmogony, by its short time scale, had made anything but the progressionist doctrine impossible. Darwin, to his great good fortune, had appeared when this hypothesis was in the process of being overthrown by Lyell. Thus Darwin, whose theories demanded a vaster grant of time than any previous worker had envisaged, wrote his book in the easygoing days of ultra-uniformitarianism, when time appeared as infinite as space. Once, for example, when Lyell in 1860 had raised some question about the slow change in insular faunas, Darwin had responded complacently, "We should ... always remember that no change will ever be effected till a variation in the habits, or structure, or of both, chance to occur in the right direction ... and this may be in any particular case indefinitely long." [32] It can easily be seen that the harsh strictures of the physicists, if they had been voiced a few years earlier, might well have reduced Darwin to silence or, at the very least, have caused him to reject natural selection as an evolutionary mechanism. Fortunately, from the historical standpoint, this did not occur, physics instead, as represented by the devout Kelvin, probably having been stimulated to an examination of earth-time, by some degree of animus toward Darwin's new heresy. The results, viewed even partially in this light, are fascinating. It can be seen, for example, that the damage done by Kelvin's doctrine to Darwin's ideas of change as involving the selection of minute and almost imperceptible variations led to a renewed search on the part of the biologists. They badly needed some mechanism of rapid organic transformation. This became particularly true as the demonstrated inviolability of the germ plasm precluded further reliance on use-inheritance or similar Lamarckian mechanisms. Thus, though the physicists originally appeared as the bette noire of this chapter, they became, wrong though they were, the indirect stimulation which played a considerable part in the emergence of the new genetics and the rediscovery of Mendel at the turn of the century. Discontinuous, saltatory evolution became the only apparent alternative to uniformitarian evolution, nor was it long in appearing. The doctrine of macro-mutations offered a way out of the Weismann-Darwin dilemma. Lest I seem to be reading connections into unrelated events long after their occurrence, the following quotation from Hugo De Vries, one of the three independent rediscoverers of Mendel's work in 1900, may prove of interest. "I have now to point out one of the weightiest objections against the conception of the origin of species by means of slow and gradual changes. It is an objection which has been brought forward against Darwin from the very beginning, which has never relented, and which often has threatened to impair the whole theory of descent. It is the incompatibility of the results concerning the age of life on this earth, as propounded by physicists and astronomers, with the demand made by the theory of descent. "The deductions made by Lord Kelvin and others from the central heat of the earth, from the rate of the production of the calcareous deposits, from the increase of the amount of salt in the seas, and from various other sources, indicate an age for the inhabitable surface of the earth of some millions of years only. The most probable estimates lie between twenty and forty millions of years. The evolutionists of the gradual line, however, had supposed many thousands of millions of years to be the smallest amount that would account for the whole range of evolution, from the very first beginning until the appearance of mankind. This large discrepancy has always been a source of doubt and a weapon in the hands of the opponents of the evolutionary idea.... The theory of evolution had to be remolded." [33] When De Vries made this statement on a lecture tour of America he was being hailed as a second Darwin -- much to the elderly Wallace's amazement -- the latter having refused to express much confidence in the newfangled Mendelian genetics whose characters he regarded as in the nature of "abnormalities or monstrosities." The reaction of Wallace to the Mendelian discoveries was not purely the product of old age. There is in it a trace of subconscious fear -- the fear, perfectly understandable in the light of the times, that Darwin and he had, after all, not been right and that they might be losing their hold on posterity. This had become particularly apparent with the rise of the "new Darwin" who had momentarily captured the public imagination. In 1886, about the time that Weismann was engaged upon his theory of the inviolability of the germ plasm, De Vries in Holland had begun to study an American plant, Oenotheraa lamarckiana, the evening primrose, which had escaped into the wild state in Europe. To his happy astonishment it seemed that he had discovered a plant actually giving birth directly to a new species -- and this in considerable profusion. Furthermore, the plant appeared to be giving off new types every year. If this phenomenon could be verified and established, a macro-mutative method of establishing new species might be demonstrable. The evolutionary rate of change could be speeded up to accord with the time scale of the physicists and Darwin's minute variations could safely be disregarded. Natural selection would then cease to be as important as it was in the first edition of the Origin. The idea of dramatic and considerable alterations at one step did not, of course, originate with De Vries. Darwin had been cognizant of the possibility so far as domesticated plants, or animals like the Ancon sheep, were concerned, but because of the problem presented by the conception of blending inheritance, he did not see how such breeds could be maintained except through the attention of the breeder. Theophilus Parsons in America, a few months after the first publication of the Origin, had dwelt on the possibility of the "hopeful monster" as a step in the creation of new species. Parsons even went so far (a courageous act in 1860) as to intimate that the earliest human beings were "children of Simiae nearest in structure to men, and were made, by some influence of variation, to differ from their progenitors...." [34] This communication of Parsons's thus anticipates Kolliker's expression of similar views upon saltatory evolution in 1864. [35] It was not until 1901, however, that De Vries, by now acquainted with Menders work, began to publish upon his discovery. He came to believe that states of mutability might alternate with periods of much greater stability in organisms which do not necessarily show such constant selection and change as had been propounded by Darwinians such as Wallace. His conclusions and the reemergence of Mendel into the limelight brought De Vries world-wide fame. There are psychological aspects to this phenomenon. Thomas Case commented in Science that the new theory should appeal particularly to theologians. "If.» he says, "we conceive that man originated abruptly by some unaccountable molecular change ... there can be no doubt of the time when man became immortal, whereas there would be necessarily much, much uncertainty as to tile time when this occurred among the successive infinitesimal increments of brain development necessitated by the Darwinian theory." [36] For a short time it appeared that some of the more repugnant aspects of Darwinian thought -- its constant emphasis upon struggle, its mechanistic, utilitarian philosophy which, to many, seemed as dingy as a Victorian factory -- might vanish away in the light of the new Mendelian discoveries arid particularly under the influence of the type of mutative change dwelt upon by De Vries. His work contained a vision in which even human evolution might appear to press forward more gracefully and rapidly than in the tooth-and-claw philosophies which had haunted Darwinian thinking. Then suddenly the dream, the popular enthusiasm, ended. De Vries, who had held for a period a position of such unrivaled popularity that he had been brought to America to give personal addresses upon his theories, is now sometimes difficult to find in the indices of introductory works on genetics. It is no fault of De Vries, who was an honest worker. Instead, it was the simple irony of fate. The man who had sought to see creation at work in a simple flower, who had held in his own hands "a species which has been taken in the very act of producing new forms," the man who had been able to say "the origin of species is no longer to be considered beyond our experience," had been working with a plant hybrid whose genetic mechanism, because of unequal chromosome numbers, had a tendency to break down. In the words of two modem geneticists, "The mutants of Oenothera are therefore nothing more than symptoms of its peculiar hybridity and as such are of little significance in evolution." [37] The acclaim has long vanished. Even by 1907 Vernon Kellogg had seen fit to comment: "The lack of new observational data ... of the origin of new species through mutations in nature, is significant. It is my belief that a reaction against the curiously swift and widespread partial to complete acceptance of the mutation theory ... will soon occur." By "mutation theory," of course, Kellogg was referring to what today we would call a large or macromutation. It would be ill to forget, however, that De Vries, like many another, had borne the heat of the scientific day. He had pursued what seemed a reality and had found a phantom, but in the process had contributed like Mendel before him to the accumulating wisdom that might be used by other men after his name and his memory had vanished from the books. There can be no doubt that in dramatizing the large, the macro-mutation, rather than the small "fluctuating" variations of the Darwinists, De Vries so emphasized discontinuity in evolution as to promote a clarification of, the problem by renewed research. Furthermore, his swift-changing kaleidoscopic evolution shifted attention from natural selection in the world of the adult organism to the processes at work in the egg or sperm cell. Cytology was coming into its own and the disproportionate emphasis upon natural selection was fading. There are still those who remember that in the thinly tenanted no man's land described by Bateson as the field of genetics in the first five years of this century, Hugo De Vries by this emphasis alone did notable work. As Bateson has remarked, it is in the seed bed, the poultry yard, and amid growing nature that variation may be found and its properties tested. [38] De Vries was to be found in these places. He was one of the very few theoretical evolutionists, after the old pigeon fancier died at Down, who did not confine himself to his study. IV. Time and Radioactivity We have now seen something of the subtle if mistaken pressures exerted indirectly upon biology from the field of physics. They had contributed to Darwin's discomfort almost from the time the Origin was published, and had played their part in his groping retreat toward Lamarck. Still, a few geologists remained suspicious. F. R. Moulton was among them. He was dubious that the contraction theory of the sun's heat was sufficient to give the necessary duration to energies radiated by that body. "Finally he pointed out in 1899 that it was conceivable that some type of unknown atomic energy might contain the secret. S. His words were indeed prophetic and were to be totally fulfilled within the next decade. In 1903 Paul Curie and Laborde demonstrated that radium steadily maintains its temperature above its surroundings. Both geology and astronomy were not slow to assess the significance of the newly discovered atomic energies. Kelvin's conception of the sun as a sort of figurative coal pile rapidly dwindling toward extinction was swept away; his harsh calculations became meaningless. Even here on earth the uranium content of the rocks was such that the doctrine of the loss of residual heat ceased to have significance. The way lay open for an enormous extension of the antiquity of the earth -- an antiquity that would have delighted and astounded Darwin. The long tyranny of the physicists was over; the oncoming cold had been a phantom. Instead of a freezing and contracting earth whose fires were dying, men now saw a planet which, in terms of human years, was well-nigh forever young, prodigal of its heat in mountain upthrusts, green with some endless and undying spring whose source lay hidden at the atom's heart. Instrument of terror though the atom in our time has come to be, it may someday be remembered that the news of radioactivity came first among us as a message that the abysmal mechanics of nineteenth-century science had perished and had left us lifting our faces with renewed faith and understanding to the sun. _______________ Notes: 1. "Twenty-five Years of Geological Progress in Britain," Nature, 1895. Vol. 51. p. 369. 2. James Marchant, Alfred Russel Wallace: Letters and Reminiscences, New York, 1916, p. 220. 3. Dated January 31, 1869. The correspondent was apparently J. Croll. See MLD, Vol. 2, pp. 163-64. 4. Report of the British Association for the Advancement of Science, Oxford, 1894, pp. 3-15. 5. O, p. 245. 6. 1862, Vol. 5, pp. 388-93. 7. W. Thomson (Lord Kelvin), "Physical Considerations Regarding the Possible Age of the Sun's Heat," The London, Edinburgh and Dublin Philosophical Magazine and Journal of Science, 1862. Series 4, Vol. 23, p. 160. 8. Cecilia Payne-Gaposchkin, Stars in the Making, Harvard University Press, 1952, pp. 106-7. 9. Reprinted In Popular Lectures and Addresses by Sir William Thomson, London, 1894, Vol. 2. pp. 6-9. 10. Anniversary Address, Quarterly Journal of the Geological Society of London, 1869, Vol. 25, p. xlviii. 11. Ibid., p. xlviii. 12. Ibid., p. xxxviii. 13. Popular Lectures and Addresses, London, 1894, Vol. 2, pp. 89-90. 14. James Marchant, Alfred Russel Wallace: Letters and Reminiscences, New York, 1916, pp. 205-6. 15. S. P. Thompson, The Life of William Thomson, London, 1910, Vol. 2, p. 637. 16. Ibid., p. 943. 17. W. J. Sollas, "The Age of the Earth," Nature, 1895, Vol. 51, p. 543. 18. "Evolution Geology," Report of the British Association for the Advancement of Science, Bradford. England, 1900, p. 722. 19. "Geologic Time, As Indicated by the Sedimentary Rocks of North America," The American Geologist, 1895, Vol. 12, p. 368. 20. ''Twenty-five Years of Geological Progress In Britain," Nature, 1895, Vol. 51, p. 369. 21. Modern Library ed., p. 256. 22. Ibid., p. 270. 23. Ibid., p. 253. This statement may also be contrasted with one which Darwin made to Hooker in 1856: "This power of selection stands in the most direct relation to time, and in the state of nature can only be excessively slow." At this date he categorically denied that time and altered conditions were "convertible terms." LLD, Vol. 2, p. 84. 24. A. R. Wallace, "On a Diagram of the Earth's Eccentricity and the Precession of the Equinoxes Illustrating their Relation to Geological Climate and the Rate of Organic Change," Report of the British Association for the Advancement of Science, 1870, p. 89. 25. Adam Sedgwick, "Variation and Some Phenomena Connected with Reproduction and Sex," Report of the British Association for the Advancement of Science, Dover, 1899, pp. 773-74. 26. Ibid., p. 774. 27. C. L. Morgan, "Geological Time," Geological Magazine, 1878, n.s.. Vol. 5, p. 155. 28. G. K. Gilbert, "Rhythms and Geologic Time," Popular Science Monthly, 1900, Vol. 57, p. 346. 29. "Purpose and Particles in the Study of Heredity; Science, Medicine and History, edited by E. A. Underwood, Oxford University Press, 1953, Vol. 2, p. 474. 30. James Marchant, Alfred Russel Wallace: Letters and Reminiscences, New York, 1916, p. 249. 31. Ibid., p. 322. 32. LLD. Vol. 2, p. 337. 33. Hugo De Vries, "The Evidence of Evolution," Science, 1904, n.s. Vol. 20, p. 398. 34. "A Communication upon Evolution," Proceedings of the Am. Academy of Arts and Sciences, 1860. Vol. 4. p. 416. Darwin was aware of Parsons's views and commented in the same year to Asa Gray that he had reflected on the possibility of "favorable monstrosities" playing a part in evolution. "It would be a great aid," he admitted, "but I did not allude to the subject, for, after much labor, I could find nothing which satisfied me of the probability of such occurrences." LLD. Vol. 2. p. 333. 35. For a discussion of Von Kolliker and other early advocates of saltatory evolution see Philip Fothergill's Historical Aspects of Organic Evolution, Hollis and Carter, London. 1952. p. 172 ff. 36. "The Mutation Theory," Science, 1905, n.s. Vol. 22. p. 309. 37. C. D. Darlington and K. Mather, The Elements of Genetics, London, 1949, p. 263. 38. William Bateson, "Heredity and Evolution," Popular Science Monthly, 1904, Vol. 65, p. 525. 39. A. C. Gifford, "The Origin of the Solar System," Scientia, 1932, Vol. 52, p. 154.
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