作者：[英]查尔斯·达尔文
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百年哈佛经典第11卷：物种起源论(英文原版)试读：
INTRODUCTORY NOTE
CHARLES ROBERT DARWIN, born at Shrewsbury, England, on February 12, 1809, came of a family of remarkable intellectual distinction which is still sustained in the present generation. His father was a successful physician with remarkable powers of observation, and his grandfather was Erasmus Darwin, the well-known author of “The Botanic Garden.” He went to school at Shrewsbury, were he failed to profit from the strict classical curriculum there in force; nor did the regular professional courses at Edinburgh University, where he spent two years studying medicine, succeed in rousing his interest. In 1827 he was entered at Christ's College, Cambridge, to study for the B. A. degree, preparatory to entering the Church; but while there his friendship with Henslow, the professor of botany, led to his enlarging his general scientific knowledge and finally to his joining the expedition of the “Beagle” in the capacity of naturalist. From this Darwin returned after a voyage of five years with a vast first-hand knowledge of geology and zoology, a reputation as a successful collector, and, most important of all, with the germinal ideas of his theory of evolution. The next few years were spent in working up the materials he had collected; but his health gave signs of breaking, and for the rest of his life he suffered constantly, but without complaint. With extraordinary courage and endurance he took up a life of seclusion and methodical regularity, and accomplished his colossal results in spite of the most severe physical handicap. He had married in 1839, and three years later he withdrew from London to the little village of Down, about sixteen miles out, where he spent the rest of his life. His custom, which was almost a method, was to work till he was on the verge of complete collapse, and then to take a holiday just sufficient to restore him to working condition.
As early as 1842 Darwin had thrown into rough form the outlines of his theory of evolution, but the enormous extent of the investigations he engaged in for the purpose of testing it led to a constant postponing of publication. Finally in June, 1858, A. R. Wallace sent him a manuscript containing a statement of an identical theory of the origin of species, which had been arrived at entirely independently. On the advice of Lyell, the geologist, and Hooker, the botanist, Wallace's paper and a letter of Darwin's of the previous year, in which he had outlined his theory to Asa Gray, were read together on July 1, 1858, and published by the Linnæan Society. In November of the following year “The Origin of Species” was published, and the great battle was begun between the old science and the new. This work was followed in 1868 by his “Variation of Animals and Plants under Domestication,” that in turn by the “Descent of Man” in 1871, and that again by “The Expression of the Emotions in Man and Animals.” Each of these books was the elaboration or complement of a section of its predecessor. The later years of Darwin's life were chiefly devoted to botanical research, and resulted in a series of treatises of the highest scientific value. He died at Down on April 19, 1882, and is buried in Westminster Abbey.
The idea of the evolution of organisms, so far from originating with Darwin, is a very old one. Glimpses of it appear in the ancient Greek philosophers, especially Empedocles and Aristotle; modern philosophy from Bacon onward shows an increasing definiteness in its grasp of the conception; and in the age preceding Darwin's, Buffon, Erasmus Darwin, and Lamarck had given it a fairly concrete expression. As we approach the date of the publication of “The Origin of Species” adherence to the doctrine not only by naturalists but by poets, such as Goethe, becomes comparatively frequent; and in the six years before the joint announcement of Darwin and Wallace, Herbert Spencer had been supporting and applying it vigorously in the field of psychology.
To these partial anticipations, however, Darwin owed little. When he became interested in the problem, the doctrine of the fixity of species was still generally held; and his solution occurred to him mainly as the result of his own observation and thinking. Speaking of the voyage of the “Beagle,” he says, “On my return home in the autumn of 1836 I immediately began to prepare my journal for publication, and then saw how many facts indicated the common descent of species.... In July (1837) I opened my first note-book for facts in relation to the Origin of Species, about which I had long reflected, and never ceased working for the next twenty years.... Had been greatly struck from about the month of previous March on character of South American fossils, and species on Galapagos Archipelago. These facts (especially latter) origin of all my views.” Again, “In October (1838), that is fifteen months after I had begun my systematic inquiry, I happened to read for amusement ‘Malthus on Population,’ and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favorable variations would tend to be preserved, and unfavorable ones to be destroyed. The result of this would be the formation of new species. Here then I had at last got a theory by which to work.”
From these statements by Darwin himself we can see how far it is from being the case that he merely gathered the ripe fruit of the labors of his predecessors. All progress is continuous, and Darwin, like other men, built on the foundations laid by others; but to say this is not to deny him originality in the only vital sense of that word. And the importance of his contribution—in verifying the doctrine of descent, in interpreting and applying it, and in revealing its bearings on all departments of the investigation of nature—is proved by the fact that his work opened a new epoch in science and philosophy. As Huxley said, “Whatever be the ultimate verdict of posterity upon this or that opinion which Mr. Darwin has propounded; whatever adumbrations or anticipations of his doctrines may be found in the writings of his predecessors; the broad fact remains that, since the publication and by reason of the publication of ‘The Origin of Species’ the fundamental conceptions and the aims of the students of living Nature have been completely changed.”
The present year (1909) has seen the celebration of the hundredth anniversary of Darwin's birth and the fiftieth anniversary of the publication of his great work. Among the numerous expressions of honor and gratitude which the world of science has poured upon his memory, none is more significant than the volume on “Darwin and Modern Science” which has been issued by the press of his old University of Cambridge. In this are collected nearly thirty papers by the leaders of modern science dealing with the influence of Darwin upon various fields of thought and research, and with the later developments and modifications of his conclusions. Biology, in many different departments, Anthropology, Geology, Psychology, Philosophy, Sociology, Religion, Language, History, and Astronomy are all represented, and the mere enumeration suggests the colossal nature of his achievement and its results.
Yet the spirit of the man was almost as wonderful as his work. His disinterestedness, his modesty, and his absolute fairness were not only beautiful in themselves, but remain as a proof of the importance of character in intellectual labor. Here is his own frank and candid summing up of his abilities: “My success as a man of science, whatever this may have amounted to, has been determined, as far as I can judge, by complex and diversified mental qualities and conditions. Of these, the most important have been—the love of science—unbounded patience in long reflecting over any subject—industry in observing and collecting facts—and a fair share of invention as well as of common sense. With such moderate abilities as I possess, it is truly surprising that I should have influenced to a considerable extent the belief of scientific men on some important points.”
AN HISTORICAL SKETCH
OF THE PROGRESS OF OPINION ONTHE ORIGIN OF SPECIESPREVIOUSLY TO THE PUBLICATION OFTHE FIRST EDITION OF THIS WORK————
I WILL here give a brief sketch of the progress of opinion on the Origin of Species. Until recently the great majority of naturalists believed that species were immutable productions, and had been separately created. This view has been ably maintained by many authors. Some few naturalists, on the other hand, have believed that species undergo modification, and that the existing forms of life are the descendants by true generation of pre-existing forms. Passing over 注1allusions to the subject in the classical writers, the first author who in modern times has treated it in a scientific spirit was Buffon But as his opinions fluctuated greatly at different periods, and as he does not enter on the causes or means of the transformation of species, I need not here enter on details.
Lamarck was the first man whose conclusions on the subject excited much attention. This justly-celebrated naturalist first published his views in 1801; he much enlarged them in 1809 in his ‘Philosophie Zoologique,’ and subsequently, in 1815, in the Introduction to his ‘Hist. Nat. des Animaux sans Vertébres.’ In these works he upholds the doctrine that species, including man, are descended from other species. He first did the eminent service of arousing attention to the probability of all change in the organic, as well as in the inorganic world, being the result of law, and not of miraculous interposition. Lamarck seems to have been chiefly led to his conclusion on the gradual change of species, by the difficulty of distinguishing species and varieties, by the almost perfect gradation of forms in certain groups, and by the analogy of domestic productions. With respect to the means of modification, he attributed something to the direct action of the physical conditions of life, something to the crossing of already existing forms, and much to use an disuse, that is, to the effects of habit. To this latter agency he seems to attribute all the beautiful adaptations in nature;— such as the long neck of the giraffe for browsing on the branches of trees. But he likewise believed in a law of progressive development; and as all the forms of life thus tend to progress, in order to account for the existence at the present day of simple productions, he maintains that such forms are now 注2spontaneously generated.
Geoffroy Saint-Hilaire, as is stated in his ‘Life,’ written by his son, suspected, as early as 1795, that what we call species are various degenerations of the same type. It was not until 1828 that he published his conviction that the same forms have not been perpetuated since the origin of all things. Geoffroy seems to have relied chiefly on the condition of life, or the “monde ambiant,” as the cause of change. He was cautious in drawing conclusions, and did not believe that existing species are now undergoing modification; and, as his son adds, “C'est donc un problème à réserver entièrement à l'avenir, supposé même que l'avenir doive avoir prise sur lui.”
In 1813, Dr. W. C. Wells read before the Royal Society ‘An Account of a White Female, part of whose skin resembles that of a Negro'; but his paper was not published until his famous ‘Two Essays upon Dew and Single Vision' appeared in 1818. In this paper he distinctly recognises the principle of natural selection, and this is the first recognition which has been indicated; but he applies it only to the races of man, and to certain characters alone. After remarking that negroes and mulattoes enjoy an immunity from certain tropical diseases, he observes, firstly, that all animals tend to vary in some degree, and, secondly, that agriculturists improve their domesticated animals by selection; and then, he adds, but what is done in this latter case “by art, seems to be done with equal efficacy, though more slowly, by nature, in the formation of varieties of mankind, fitted for the country which they inhabit. Of the accidental varieties of man, which would occur among the first few and scattered inhabitants of the middle regions of Africa, some one would be better fitted than the others to bear the diseases of the country. This race would consequently multiply, while the others would decrease; not only from their inability to sustain the attacks of disease, but from their incapacity of contending with their more vigorous neighbours. The colour of this vigorous race I take for granted, from what has been already said, would be dark. But the same disposition to form varieties still existing, a darker and a darker race would in the course of time occur: and as the darkest would be the best fitted for the climate, this would at length become the most prevalent, if not the only race, in the particular country in which it had originated.” He then extends these same views to the white inhabitants of colder climates. I am indebted to Mr. Rowley, of the United States, for having called my attention, through Mr. Brace, to the above passage in Dr. Wells's work.
The Hon. and Rev. W. Herbert, afterwards Dean of Manchester, in the fourth volume of the ‘Horticultural Transactions,’ 1822, and in his work of the ‘Amaryllidaceæ’ (1837, pp. 19, 339), declares that ‘horticultural experiments have established, beyond the possibility of refutation, that botanical species are only a higher and more permanent class of varieties.’ He extends the same view to animals. The Dean believes that single species of each genus were created in an originally highly plastic condition, and that these have produced, chiefly by intercrossing, but likewise by variation, all our existing species.
In 1826 Professor Grant, in the concluding paragraph in his well-known paper (‘Edinburgh Philosophical Journal,’ vol. xiv. p. 283) on the Spongilla, clearly declares his belief that species are descended from other species, and that they become improved in the course of modification. This same view was given in his Fifty-fifth Lecture, published in the ‘Lancet’ in 1834.
In 1831 Mr. Patrick Matthew published his work on ‘Naval Timber and Arboriculture,’ in which he gives precisely the same view on the origin of species as that (presently to be alluded to) propounded by Mr. Wallace and myself in the ‘Linnean Journal,’ and as that enlarged in the present volume. Unfortunately the view was given by Mr. Matthew very briefly in scattered passages in an appendix to a work on a different subject, so that it remained unnoticed until Mr. Matthew himself drew attention to it in the ‘Gardener's Chronicle,’ on April 7th, 1860. The differences of Mr. Matthew's view from mine are not of much importance: he seems to consider that the world was nearly depopulated at successive periods, and then re-stocked; and he gives as an alternative, that new forms may be generated “without the presence of any mould or germ of former aggregates.” I am not sure that I understand some passages; but it seems that he attributes much influence to the direct action of the conditions of life. He clearly saw, however, the full force of the principle of natural selection.
The celebrated geologist and naturalist, Von Buch, in his excellent ‘Description Physique des Isles Canaries’ (1836, p. 147), clearly expresses his belief that varieties slowly become changed into permanent species, which are no longer capable of intercrossing.
Rafinesque, in his ‘New Flora of North America,’ published in 1836, wrote (p. 6) as follows:—“All species might have been varieties once, and many varieties are gradually becoming species by assuming constant and peculiar characters”; but farther on (p. 18) he adds, “except the original types or ancestors of the genus.”
In 1843-44 Professor Haldeman (‘Boston Journal of Nat. Hist. U. States,’ vol. iv. p. 468) has ably given the arguments for and against the hypothesis of the development and modification of species: he seems to lean towards the side of change.
The ‘Vestiges of Creation’ appeared in 1844. In the tenth and much improved edition (1853) the anonymous author says (p. 155):—“The proposition determined on after much consideration is, that the several series of animated beings, from the simplest and oldest up to the highest and most recent, are, under the providence of God, the results, first, of an impulse which has been imparted to the forms of life, advancing them, in definite times, by generation, through grades of organisation terminating in the highest dicotyledons and vertebrata, these grades being few in number, and generally marked by intervals of organic character, which we find to be a practical difficulty in ascertaining affinities; second, of another impulse connected with the vital forces, tending, in the course of generations, to modify organic structures in accordance with external circumstances, as food, the nature of the habitat, and the meteoric agencies, these being the ‘adaptations’ of the natural theologian.” The author apparently believes that organisation progresses by sudden leaps, but that the effects produced by the conditions of life are gradual. He argues with much force on general grounds that species are not immutable productions. But I cannot see how the two supposed “impulses” account in a scientific sense for the numerous and beautiful co-adaptations which we see throughout nature; I cannot see that we thus gain any insight how, for instance, a woodpecker has become adapted to its peculiar habits of life. The work, from its powerful and brilliant style, though displaying in the earlier editions little accurate knowledge and a great want of scientific caution, immediately had a very wide circulation. In my opinion it has done excellent service in this country in calling attention to the subject, in removing prejudice, and in thus preparing the ground for the reception of analogous views.
In 1846 the veteran geologist M. J. d'Omalius d'Halloy published in an excellent though short paper (‘Bulletins de l'Acad. Roy. Bruxelles,’ tom. xiii. p. 581) his opinion that it is more probable that new species have been produced by descent with modification than that they have been separately created: the author first promulgated this opinion in 1831.
Professor Owen, in 1849 (‘Nature of Limbs,’ p. 86), wrote as follows:— “The archetypal idea was manifested in the flesh under diverse such modifications, upon this planet, long prior to the existence of those animal species that actually exemplify it. To what natural laws or secondary causes the orderly succession and progression of such organic phenomena may have been committed, we, as yet, are ignorant.” In his address to the British Association, in 1858, he speaks (p. li.) of “the axiom of the continuous operation of creative power, or of the ordained becoming of living things.” Farther on (p. xc.), after referring to geographical distribution, he adds, “These phenomena shake our confidence in the conclusion that the Apteryx of New Zealand and the Red Grouse of England were distinct creations in and for those islands respectively. Always, also, it may be well to bear in mind that by the word ‘creation’ the zoologist means ‘a process he knows not what.’“ He amplifies this idea by adding that when such cases as that of the Red Grouse are “enumerated by the zoologist as evidence of distinct creation of the bird in and for such islands, he chiefly expresses that he knows not how the Red Grouse came to be there, and there exclusively; signifying also, by this mode of expressing such ignorance, his belief that both the bird and the islands owed their origin to a great first Creative Cause.” If we interpret these sentences given in the same address, one by the other, it appears that this eminent philosopher felt in 1858 his confidence shaken that the Apteryx and the Red Grouse first appeared in their respective homes, “he knew not how,” or by some process “he knew not what.”
This address was delivered after the papers by Mr. Wallace and myself on the Origin of Species, presently to be referred to, had been read before the Linnean Society. When the first edition of this work was published, I was so completely deceived, as were many others, by such expressions as “the continuous operation of creative power,” that I included Professor Owen with other palæontologists as being firmly convinced of the immutability of species; but it appears (‘Anat. of Vertebrates,’ vol. iii. p. 796) that this was on my part a preposterous error. In the last edition of this work I inferred, and the inference still seems to me perfectly just, from a passage beginning with the words “no doubt the type-form,” &c. (Ibid., vol. i. p. xxxv.), that Professor Owen admitted that natural selection may have done something in the formation of a new species; but this it appears (Ibid., vol. iii. p. 798) is inaccurate and without evidence. I also gave some extracts from a correspondence between Professor Owen and the Editor of the ‘London Review,’ from which it appeared manifest to the Editor as well as to myself, that Professor Owen claimed to have promulgated the
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