Chapter 2

Lamarck[21] (1744-1829) seems to have thought out his theory of evolution without any knowledge of Erasmus Darwin's which it closely resembled. The central idea of his theory was the cumulative inheritance of functional modifications. "Changes in environment bring about changes in the habits of animals. Changes in their wants necessarily bring about parallel changes in their habits. If new wants become constant or very lasting, they form new habits, the new habits involve the use of new parts, or a different use of old parts, which results finally in the production of new organs and the modification of old ones." He differed from Buffon in not attaching importance, as far as animals are concerned, to the direct influence of the environment, "for environment can effect no direct change whatever upon the organisation of animals," but in regard to plants he agreed with Buffon that external conditions directly moulded them.

Treviranus[22] (1776-1837), whom Huxley ranked beside Lamarck, was on the whole Buffonian, attaching chief importance to the influence of a changeful environment both in modifying and in eliminating, but he was also Goethian, for instance in his idea that species like individuals pass through periods of growth, full bloom, and decline. "Thus, it is not only the great catastrophes of Nature which have caused extinction, but the completion of cycles of existence, out of which new cycles have begun." A characteristic sentence is quoted by Prof. Osborn: "In every living being there exists a capability of an endless variety of form-assumption; each possesses the power to adapt its organisation to the changes of the outer world, and it is this power, put into action by the change of the universe, that has raised the simple zoophytes of the primitive world to continually higher stages of organisation, and has introduced a countless variety of species into animate Nature."

Goethe[23] (1749-1832), who knew Buffon's work but not Lamarck's, is peculiarly interesting as one of the first to use the evolution-idea as a guiding hypothesis, e.g. in the interpretation of vestigial structures in man, and to realise that organisms express an attempt to make a compromise between specific inertia and individual change. He gave the finest expression that science has yet known--if it has known it--of the kernel-idea of what is called "bathmism," the idea of an "inherent growth-force"--and at the same time he held that "the way of life powerfully reacts upon all form" and that the orderly growth of form "yields to change from externally acting causes."

Besides Buffon, Erasmus Darwin, Lamarck, Treviranus, and Goethe, there were other "pioneers of evolution," whose views have been often discussed and appraised. Étienne Geoffroy Saint-Hilaire (1772-1884), whose work Goethe so much admired, was on the whole Buffonian, emphasising the direct action of the changeful _milieu_. "Species vary with their environment, and existing species have descended by modification from earlier and somewhat simpler species." He had a glimpse of the selection idea, and believed in mutations or sudden leaps--induced in the embryonic condition by external influences. The complete history of evolution-theories will include many instances of guesses at truth which were afterwards substantiated, thus the geographer von Buch (1773-1853) detected the importance of the Isolation factor on which Wagner, Romanes, Gulick and others have laid great stress, but we must content ourselves with recalling one other pioneer, the author of the _Vestiges of Creation_ (1844), a work which passed through ten editions in nine years and certainly helped to harrow the soil for Darwin's sowing. As Darwin said, "it did 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."[24] Its author, Robert Chambers (1802-1871) was in part a Buffonian--maintaining that environment moulded organisms adaptively, and in part a Goethian--believing in an inherent progressive impulse which lifted organisms from one grade of organisation to another.

_As Regards Natural Selection_

The only thinker to whom Darwin was directly indebted, so far as the theory of Natural Selection is concerned, was Malthus, and we may once more quote the well-known passage in the Autobiography: "In October, 1838, that is, fifteen months after I had begun my systematic enquiry, 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 favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The result of this would be the formation of new species."[25]

Although Malthus gives no adumbration of the idea of Natural Selection in his exposition of the eliminative processes which go on in mankind, the suggestive value of his essay is undeniable, as is strikingly borne out by the fact that it gave to Alfred Russel Wallace also "the long-sought clue to the effective agent in the evolution of organic species."[26] One day in Ternate when he was resting between fits of fever, something brought to his recollection the work of Malthus which he had read twelve years before. "I thought of his clear exposition of 'the positive checks to increase'--disease, accidents, war, and famine--which keep down the population of savage races to so much lower an average than that of more civilized peoples. It then occurred to me that these causes or their equivalents are continually acting in the case of animals also; and as animals usually breed much more rapidly than does mankind, the destruction every year from these causes must be enormous in order to keep down the numbers of each species, since they evidently do not increase regularly from year to year, as otherwise the world would long ago have been densely crowded with those that breed most quickly. Vaguely thinking over the enormous and constant destruction which this implied, it occurred to me to ask the question, Why do some die and some live? And the answer was clearly, that on the whole the best fitted live. From the effects of disease the most healthy escaped; from enemies the strongest, the swiftest, or the most cunning; from famine the best hunters or those with the best digestion; and so on. Then it suddenly flashed upon me that this self-acting process would necessarily _improve the race_, because in every generation the inferior would inevitably be killed off and the superior would remain--that is, _the fittest would survive_."[27] We need not apologise for this long quotation, it is a tribute to Darwin's magnanimous colleague, the Nestor of the evolutionist camp,--and it probably indicates the line of thought which Darwin himself followed. It is interesting also to recall the fact that in 1852, when Herbert Spencer wrote his famous _Leader_ article on "The Development Hypothesis" in which he argued powerfully for the thesis that the whole animate world is the result of an age-long process of natural transformation, he wrote for _The Westminster Review_ another important essay, "A Theory of Population deduced from the General Law of Animal Fertility," towards the close of which he came within an ace of recognising that the struggle for existence was a factor in organic evolution. At a time when pressure of population was practically interesting men's minds, Darwin, Wallace, and Spencer were being independently led from a social problem to a biological theory. There could be no better illustration, as Prof. Patrick Geddes has pointed out, of the Comtian thesis that science is a "social phenomenon."

Therefore, as far more important than any further ferreting out of vague hints of Natural Selection in books which Darwin never read, we would indicate by a quotation the view that the central idea in Darwinism is correlated with contemporary social evolution. "The substitution of Darwin for Paley as the chief interpreter of the order of nature is currently regarded as the displacement of an anthropomorphic view by a purely scientific one: a little reflection, however, will show that what has actually happened has been merely the replacement of the anthropomorphism of the eighteenth century by that of the nineteenth. For the place vacated by Paley's theological and metaphysical explanation has simply been occupied by that suggested to Darwin and Wallace by Malthus in terms of the prevalent severity of industrial competition, and those phenomena of the struggle for existence which the light of contemporary economic theory has enabled us to discern, have thus come to be temporarily exalted into a complete explanation of organic progress."[28] It goes without saying that the idea suggested by Malthus was developed by Darwin into a biological theory which was then painstakingly verified by being used as an interpretative formula, and that the validity of a theory so established is not affected by what suggested it, but the practical question which this line of thought raises in the mind is this: if Biology did thus borrow with such splendid results from social theory, why should we not more deliberately repeat the experiment?

Darwin was characteristically frank and generous in admitting that the principle of Natural Selection had been independently recognised by Dr. W. C. Wells in 1813 and by Mr. Patrick Matthew in 1831, but he had no knowledge of these anticipations when he published the first edition of _The Origin of Species_. Wells, whose "Essay on Dew" is still remembered, read in 1813 before the Royal Society a short paper entitled "An Account of a White Female, part of whose skin resembles that of a Negro" (published in 1818). In this communication, as Darwin said, "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.'"[29] Thus Wells had the clear idea of survival dependent upon a favourable variation, but he makes no more use of the idea and applies it only to man. There is not in the paper the least hint that the author ever thought of generalising the remarkable sentence quoted above.

Of Mr. Patrick Matthew, who buried his treasure in an appendix to a work on _Naval Timber and Arboriculture_, Darwin said that "he clearly saw the full force of the principle of natural selection." In 1860 Darwin wrote--very characteristically--about this to Lyell: "Mr. Patrick Matthew publishes a long extract from his work on _Naval Timber and Arboriculture_, published in 1831, in which he briefly but completely anticipates the theory of Natural Selection. I have ordered the book, as some passages are rather obscure, but it is certainly, I think, a complete but not developed anticipation. Erasmus always said that surely this would be shown to be the case some day. Anyhow, one may be excused in not having discovered the fact in a work on Naval Timber."[30]

De Quatrefages and De Varigny have maintained that the botanist Naudin stated the theory of evolution by natural selection in 1852. He explains very clearly the process of artificial selection, and says that in the garden we are following Nature's method. "We do not think that Nature has made her species in a different fashion from that in which we proceed ourselves in order to make our variations." But, as Darwin said, "he does not show how selection acts under nature." Similarly it must be noted in regard to several pre-Darwinian pictures of the struggle for existence (such as Herder's, who wrote in 1790 "All is in struggle ... each one for himself" and so on), that a recognition of this is only the first step in Darwinism.

Profs. E. Perrier and H. F. Osborn have called attention to a remarkable anticipation of the selection-idea which is to be found in the speculations of Étienne Geoffroy Saint-Hilaire (1825-1828) on the evolution of modern Crocodilians from the ancient Teleosaurs. Changing environment induced changes in the respiratory system and far-reaching consequences followed. The atmosphere, acting upon the pulmonary cells, brings about "modifications which are favourable or destructive ('funestes'); these are inherited, and they influence all the rest of the organisation of the animal because if these modifications lead to injurious effects the animals which exhibit them perish and are replaced by others of a somewhat different form, a form changed so as to be adapted to (à la convenance) the new environment."

Prof. E. B. Poulton[31] has shown that the anthropologist James Cowles Prichard (1786-1848) must be included even in spite of himself among the precursors of Darwin. In some passages of the second edition of his _Researches into the Physical History of Mankind_ (1826), he certainly talks evolution and anticipates Prof. Weismann in denying the transmission of acquired characters. He is, however, sadly self-contradictory and his evolutionism weakens in subsequent editions--the only ones that Darwin saw. Prof. Poulton finds in Prichard's work a recognition of the operation of Natural Selection. "After inquiring how it is that 'these varieties are developed and preserved in connexion with particular climates and differences of local situation,' he gives the following very significant answer: 'One cause which tends to maintain this relation is obvious. Individuals and families, and even whole colonies perish and disappear in climates for which they are, by peculiarity of constitution, not adapted. Of this fact proofs have been already mentioned.'" Mr. Francis Darwin and Prof. A. C. Seward discuss Prichard's "anticipations" in _More Letters of Charles Darwin_, Vol. _I._ p. 43, and come to the conclusion that the evolutionary passages are entirely neutralised by others of an opposite trend. There is the same difficulty with Buffon.

Hints of the idea of Natural Selection have been detected elsewhere. James Watt,[32] for instance, has been reported as one of the anticipators (1851). But we need not prolong the inquiry further, since Darwin did not know of any anticipations until after he had published the immortal work of 1859, and since none of those who got hold of the idea made any use of it. What Darwin did was to follow the clue which Malthus gave him, to realise, first by genius and afterwards by patience, how the complex and subtle struggle for existence works out a natural selection of those organisms which vary in the direction of fitter adaptation to the conditions of their life. So much success attended his application of the Selection-formula that for a time he regarded Natural Selection as almost the sole factor in evolution, variations being pre-supposed; gradually, however, he came to recognise that there was some validity in the factors which had been emphasised by Lamarck and by Buffon, and in his well known summing up in the sixth edition of the _Origin_ he says of the transformation of species: "This has been effected chiefly through the natural selection of numerous successive, slight, favourable variations; aided in an important manner by the inherited effects of the use and disuse of parts; and in an unimportant manner, that is, in relation to adaptive structures, whether past or present, by the direct action of external conditions, and by variations which seem to us in our ignorance to arise spontaneously."

To sum up: the idea of organic evolution, older than Aristotle, slowly developed from the stage of suggestion to the stage of verification, and the first convincing verification was Darwin's; from being an _a priori_ anticipation it has become an interpretation of nature, and Darwin is still the chief interpreter; from being a modal interpretation it has advanced to the rank of a causal theory, the most convincing part of which men will never cease to call Darwinism.

FOOTNOTES:

[Footnote 1: _Columbia University Biological Series_, Vol. I. New York and London, 1894. We must acknowledge our great indebtedness to this fine piece of work.]

[Footnote 2: _op. cit._ p. 41.]

[Footnote 3: See G. J. Romanes, "Aristotle as a Naturalist," _Contemporary Review_, Vol. lix. p. 275, 1891; G. Pouchet, _La Biologie Aristotélique_, Paris, 1885; E. Zeller, _A History of Greek Philosophy_, London, 1881, and "Ueber die griechischen Vorgänger Darwin's," _Abhandl. Berlin Akad._ 1878, pp. 111-124.]

[Footnote 4: _op. cit._ p. 81.]

[Footnote 5: _op. cit._ p. 87.]

[Footnote 6: See Brock, "Die Stellung Kant's zur Deszendenztheorie," _Biol. Centralbl._ viii. 1889, pp. 641-648. Fritz Schultze, _Kant und Darwin_, Jena, 1875.]

[Footnote 7: Mr. Alfred Russel Wallace writes: "We claim for Darwin that he is the Newton of natural history, and that, just so surely as that the discovery and demonstration by Newton of the law of gravitation established order in place of chaos and laid a sure foundation for all future study of the starry heavens, so surely has Darwin, by his discovery of the law of natural selection and his demonstration of the great principle of the preservation of useful variations in the struggle for life, not only thrown a flood of light on the process of development of the whole organic world, but also established a firm foundation for all future study of nature" (_Darwinism_, London, 1889, p. 9). See also Prof. Karl Pearson's _Grammar of Science_ (2nd edit.), London, 1900, p. 32. See Osborn, _op. cit._ p. 100.]

[Footnote 8: _Experimental Evolution_. London, 1892. Chap. I. p. 14.]

[Footnote 9: See J. Arthur Thomson, _The Science of Life_. London, 1899, Chap. XVI. "Evolution of Evolution Theory."]

[Footnote 10: See Carus Sterne (Ernst Krause), _Die allgemeine Weltanschauung in ihrer historischen Entwickelung_. Stuttgart, 1889. Chapter entitled "Beständigkeit oder Veränderlichkeit der Naturwesen."]

[Footnote 11: _Zoonomia, or the Laws of Organic Life_, 2 vols. London, 1794; Osborn, _op. cit._ p. 145.]

[Footnote 12: See Alpheus S. Packard, _Lamarck, the Founder of Evolution, His Life and Work, with Translations of his writings on Organic Evolution_. London, 1901.]

[Footnote 13: See Edward Clodd, _Pioneers of Evolution_, London, p. 161, 1897.]

[Footnote 14: See Chapter ix. "The Genetic View of Nature" in J. T. Merz's _History of European Thought in the Nineteenth Century_, Vol. 2, Edinburgh and London, 1903.]

[Footnote 15: See Prof. W. A. Locy's _Biology and its Makers_. New York, 1908. Part II. "The Doctrine of Organic Evolution."]

[Footnote 16: Presidential Address to the British Association meeting at Dublin in 1908.]

[Footnote 17: See in particular Samuel Butler, _Evolution Old and New_, London, 1879; J. L. de Lanessan, "Buffon et Darwin," _Revue Scientifique_, XLIII. pp. 385-391, 425-432, 1889.]

[Footnote 18: _op. cit._ p. 136.]

[Footnote 19: See Ernest Krause and Charles Darwin, _Erasmus Darwin_, London, 1879.]

[Footnote 20: Osborn, _op. cit._ p. 142.]

[Footnote 21: See E. Perrier, _La Philosophie Zoologique avant Darwin_, Paris, 1884; A. de Quatrefages, _Darwin et ses Précurseurs Français_, Paris, 1870; Packard, _op. cit._; also Claus, _Lamarck als Begründer der Descendenzlehre_, Wien, 1888; Haeckel, _Natural History of Creation_, Eng. transl. London, 1879; Lang, _Zur Charakteristik der Forschungswege von Lamarck und Darwin_, Jena, 1889.]

[Footnote 22: See Huxley's article "Evolution in Biology," _Encyclopaedia Britannica_ (9th edit.), 1879, pp. 744-751, and Sully's article, "Evolution in Philosophy," _ibid._ pp. 751-772.]

[Footnote 23: See Haeckel, _Die Naturanschauung von Darwin, Goethe und Lamarck_, Jena, 1882.]

[Footnote 24: _Origin of Species_ (6th edit.), p. xvii.]

[Footnote 25: _The Life and Letters of Charles Darwin_, Vol. 1. p. 83. London, 1887.]

[Footnote 26: A. R. Wallace, _My Life, a Record of Events and Opinions_, London, 1905, Vol. 1, p. 232.]

[Footnote 27: _My Life_, Vol. 1. p. 361.]

[Footnote 28: P. Geddes. article "Biology." _Chambers's Encyclopaedia._]

[Footnote 29: _Origin of Species_ (6th edit.), p. xv.]

[Footnote 30: _Life and Letters_, II, p. 301.]

[Footnote 31: _Science Progress_, New Series, Vol. 1. 1897. "A Remarkable Anticipation of Modern Views on Evolution." See also Chap. VI. in _Essays on Evolution_, Oxford, 1908.]

[Footnote 32: See Prof. Patrick Geddes's article "Variation and Selection," _Encyclopaedia Britannica_ (9th edit.) 1888.]

II

THE SELECTION THEORY

BY AUGUST WEISMANN

_Professor of Zoology in the University of Freiburg_ (_Baden_)

I. THE IDEA OF SELECTION

Many and diverse were the discoveries made by Charles Darwin in the course of a long and strenuous life, but none of them has had so far-reaching an influence on the science and thought of his time as the theory of selection. I do not believe that the theory of evolution would have made its way so easily and so quickly after Darwin took up the cudgels in favour of it if he had not been able to support it by a principle which was capable of solving, in a simple manner, the greatest riddle that living nature presents to us,--I mean the purposiveness of every living form relative to the conditions of its life and its marvellously exact adaptation to these.

Everyone knows that Darwin was not alone in discovering the principle of selection, and that the same idea occurred simultaneously and independently to Alfred Russel Wallace. At the memorable meeting of the Linnean Society on 1st July, 1858, two papers were read (communicated by Lyell and Hooker) both setting forth the same idea of selection. One was written by Charles Darwin in Kent, the other by Alfred Wallace in Ternate, in the Malay Archipelago. It was a splendid proof of the magnanimity of these two investigators, that they thus in all friendliness and without envy, united in laying their ideas before a scientific tribunal: their names will always shine side by side as two of the brightest stars in the scientific sky.

The idea of selection set forth by the two naturalists was at the time absolutely new, but it was also so simple that Huxley could say of it later, "How extremely stupid not to have thought of that." As Darwin was led to the general doctrine of descent, not through the labours of his predecessors in the early years of the century, but by his own observations, so it was in regard to the principle of selection. He was struck by the innumerable cases of adaptation, as, for instance, that of the woodpeckers and tree-frogs to climbing, or the hooks and feather-like appendages of seeds, which aid in the distribution of plants, and he said to himself that an explanation of adaptations was the first thing to be sought for in attempting to formulate a theory of evolution.

But since adaptations point to _changes_ which have been undergone by the ancestral forms of existing species, it is necessary, first of all, to inquire how far species in general are _variable_. Thus Darwin's attention was directed in the first place to the phenomenon of variability, and the use man has made of this, from very early times, in the breeding of his domesticated animals and cultivated plants. He inquired carefully how breeders set to work, when they wished to modify the structure and appearance of a species to their own ends, and it was soon clear to him that _selection for breeding purposes_ played the chief part.

But how was it possible that such processes should occur in free nature? Who is here the breeder, making the selection, choosing out one individual to bring forth offspring and rejecting others? That was the problem that for a long time remained a riddle to him.