Charles darwin origin of the species


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Charles darwin origin of the species

  3. 3. Charles Darwin (1809-1882)Born at Shrewsbury, Darwin came from an affluent family, descendedfrom successful country doctors on one side and the Wedgwood family(of pottery fame) on the other. He was intended to follow the familytradition of medicine, but couldn’t stand the bloody nature of surgery,and seemed likely to become a wastrel. His father sent him toCambridge to study theology with a view to turning him into a countryparson, but Darwin became fascinated by geology and natural history,impressing his tutors so much that they recommended him for avacancy that arose as an unpaid naturalist and companion for theCaptain on the voyage of the Beagle. The round-the-world voyagelasted from 1831 to 1836, and gave Darwin a rare insight into thegeology of different parts of the globe and the variety of life on Earth. Back home, he found he had a reputation as a geologist, based onthe reports and materials he had sent back during the voyage, but wasnot known as a naturalist at all. Although he almost immediately cameup with the idea of natural selection, he set about establishing areputation in biology before thinking about publishing it. Indeed, he onlypublished at all when Alfred Russel Wallace came up with the sameidea independently. Darwin was a semi-invalid for most of his life, perhaps a result of atropical infection picked up on the voyage, and lived in seclusion in Kentsurrounded by a large family and attended by a loving wife.Independently wealthy (and made more so by the success of his books)he never had to work for a living —but, paradoxically, worked far harderthan most people (when he was well enough) at what strictly has to becalled his hobby. John Gribbin
  4. 4. Contents PageAn Historical Sketch 5Introduction 16Chapter One Variation Under Domestication 21Chapter Two Variation Under Nature 51Chapter Three Struggle for Existence 64Chapter Four Natural Selection 80Chapter Five Laws of Variation 121Chapter Six Difficulties on Theory 152Chapter Seven Instinct 181Chapter Eight Hybridism 211Chapter Nine On the Imperfection of the Geological Record 237Chapter Ten On the Geological Succession of Organic Beings 263Chapter Eleven Geographical Distribution 290Chapter Twelve Geographical Distribution—continued 319Chapter Thirteen Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs 341Chapter Fourteen Recapitulation and Conclusion 379Glossary 404
  5. 5. Origin of Species 5 AN HISTORICAL SKETCH OF THE PROGRESS OF OPINION ON THE ORIGIN OF SPECIESPREVIOUSLY TO THE PUBLICATION OF THE FIRST EDITION OF THIS WORKI WILL here give a brief sketch of the progress of opinion on the Originof Species. Until recently the great majority of naturalists believed thatspecies were immutable productions, and had been separatelycreated. This view has been ably maintained by many authors. Somefew naturalists, on the other hand, have believed that species undergomodification, and that the existing forms of life are the descendants bytrue generation of pre-existing forms. Passing over allusions to thesubject in the classical writers,* the first author who in modern timeshas treated it in a scientific spirit was Buffon. But as his opinionsfluctuated greatly at different periods, and as he does not enter on thecauses or means of the transformation of species, I need not here enteron details.*Aristotle, in his ‘Physicae Auscultationes’ (lib. 2, cap. 8, s. 2), after remarkingthat rain does not fall in order to make the corn grow, any more than it falls tospoil the farmer’s corn when threshed out of doors, applies the same argumentto organization: and adds (as translated by Mr Clair Grece, who first pointedout the passage to me), ‘So what hinders the different parts [of the body] fromhaving this merely accidental relation in nature? as the teeth, for example, growby necessity, the front ones sharp, adapted for dividing, and the grinders flat,and serviceable for masticating the food; since they were not made for the sakeof this, but it was the result of accident. And in like manner as to the other partsin which there appears to exist an adaptation to an end. Wheresoever,therefore, all things together (that is all the parts of one whole) happened likeas if they were made for the sake of something, these were preserved, havingbeen appropriately constituted by an internal spontaneity; and whatsoeverthings were not thus constituted, perished, and still perish.’ We here see the
  6. 6. Origin of Species AN HISTORICAL SKETCH 6principle of natural selection shadowed forth, but how little Aristotle fullycomprehended the principle, is shown by his remarks on the formation of theteeth. Lamarck was the first man whose conclusions on the subject excitedmuch attention. This justly-celebrated naturalist first published hisviews in 1801; he much enlarged them in 1809 in his ‘PhilosophieZoologique,’ and subsequently, in 1815, in the Introduction to his ‘Hist.Nat. des Animaux sans Vertébres.’ In these works he upholds thedoctrine that species, including man, are descended from otherspecies. He first did the eminent service of arousing attention to theprobability of all change in the organic, as well as in the inorganic world,being the result of law, and not of miraculous interposition. Lamarckseems to have been chiefly led to his conclusion on the gradual changeof species, by the difficulty of distinguishing species and varieties, bythe almost perfect gradation of forms in certain groups, and by theanalogy of domestic productions. With respect to the means ofmodification, he attributed something to the direct action of the physicalconditions of life, something to the crossing of already existing forms,and much to use and disuse, that is, to the effects of habit. To this latteragency he seemed to attribute all the beautiful adaptations in nature;– such as the long neck of the giraffe for browsing on the branches oftrees. 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 forthe existence at the present day of simple productions, he maintainsthat such forms are now spontaneously generated.** I have taken the date of the first publication of Lamarck from Isid. GeoffroySaint-Hilaire’s (‘Hist. Nat. Générale,’ tom. ii. p. 405, 1859) excellent history ofopinion on this subject. In this work a full account is given of Buffon’sconclusions on the same subject. It is curious how largely my grandfather, DrErasmus Darwin, anticipated the views and erroneous grounds of opinion ofLamarck in his ‘Zoonomia’ (vol. i. pp. 500-510), published in 1794. Accordingto Isid. Geoffroy there is no doubt that Goethe was an extreme partisan of similarviews, as shown in the Introduction to a work written in 1794 and 1795, but notpublished till long afterwards: he has pointedly remarked (‘Goethe als
  7. 7. Origin of Species AN HISTORICAL SKETCH 7Naturforscher,’ von Dr Karl Meding, s. 34) that the future question for naturalistswill be how, for instance, cattle got their horns, and not for what they are used.It is rather a singular instance of the manner in which similar views arise atabout the same time, that Goethe in Germany, Dr Darwin in England, andGeoffroy Saint-Hilaire (as we shall immediately see) in France, came to thesame conclusion on the origin of species, in the years 1794-5. Geoffroy Saint-Hilaire, as is stated in his ‘Life,’ written by his son,suspected, as early as 1795, that what we call species are variousdegenerations of the same type. It was not until 1828 that he publishedhis conviction that the same forms have not been perpetuated sincethe origin of all things. Geoffroy seems to have relied chiefly on theconditions of life, or the ‘monde ambiant’ as the cause of change. Hewas cautious in drawing conclusions, and did not believe that existingspecies are now undergoing modification; and, as his son adds, ‘C’estdonc un problème à réserver entièrement à l’avenir, supposé mêmeque l’avenir doive avoir prise sur lui.’ In 1813, Dr W. C. Wells read before the Royal Society ‘An Accountof a White female, part of whose skin resembled that of a Negro’; buthis paper was not published until his famous ‘Two Essays upon Dewand Single Vision’ appeared in 1818. In this paper he distinctlyrecognises the principle of natural selection, and this is the firstrecognition which has been indicated; but he applies it only to the racesof man, and to certain characters alone. After remarking that negroesand mulattoes enjoy an immunity from certain tropical diseases, heobserves, firstly, that all animals tend to vary in some degree, and,secondly, that agriculturists improve their domesticated animals byselection; 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 theyinhabit. Of the accidental varieties of man, which would occur amongthe first few and scattered inhabitants of the middle regions of Africa,some one would be better fitted than the others to bear the diseasesof the country. This race would consequently multiply, while the otherswould decrease; not only from their inability to sustain the attacks of
  8. 8. Origin of Species AN HISTORICAL SKETCH 8disease, but from their incapacity of contending with their more vigorousneighbours. The colour of this vigorous race I take for granted, fromwhat has been already said, would be dark. But the same dispositionto form varieties still existing, a darker and a darker race would in thecourse of time occur: and as the darkest would be the best fitted for theclimate, this would at length become the most prevalent, if not the onlyrace, in the particular country in which it had originated.’ He thenextends these same views to the white inhabitants of colder climates.I am indebted to Mr Rowley, of the United States, for having called myattention, through Mr Brace, to the above passage in Dr Wells’ work. The Hon. and Rev. W. Herbert, afterwards Dean of Manchester, inthe fourth volume of the ‘Horticultural Transactions,’ 1822, and in hiswork on the ‘Amaryllidaceae’ (1837, pp. 19, 339), declares that‘horticultural experiments have established, beyond the possibility ofrefutation, that botanical species are only a higher and more permanentclass of varieties.’ He extends the same view to animals. The Deanbelieves that single species of each genus were created in an originallyhighly plastic condition, and that these have produced, chiefly byintercrossing, but likewise by variation, all our existing species. In 1826 Professor Grant, in the concluding paragraph in hiswell-known paper (‘Edinburgh Philosophical Journal,’ vol. xiv. p. 283)on the Spongilla, clearly declares his belief that species are descendedfrom other species, and that they become improved in the course ofmodification. This same view was given in his 55th Lecture, publishedin the ‘Lancet’ in 1834. In 1831 Mr Patrick Matthew published his work on ‘Naval Timber andArboriculture,’ in which he gives precisely the same view on the originof species as that (presently to be alluded to) propounded by MrWallace and myself in the ‘Linnean Journal,’ and as that enlarged inthe present volume. Unfortunately the view was given by Mr Matthewvery briefly in scattered passages in an Appendix to a work on adifferent subject, so that it remained unnoticed until Mr Matthew himselfdrew attention to it in the ‘Gardener’s Chronicle,’ on April 7th, 1860.The differences of Mr Matthew’s view from mine are not of muchimportance; he seems to consider that the world was nearly
  9. 9. Origin of Species AN HISTORICAL SKETCH 9depopulated at successive periods, and then re-stocked; and he givesas an alternative, that new forms may be generated ‘without thepresence of any mould or germ of former aggregates.’ I am not surethat I understand some passages; but it seems that he attributes muchinfluence 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), clearlyexpresses his belief that varieties slowly become changed intopermanent 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 assumingconstant and peculiar characters’; but farther on (p.18) he adds, ‘exceptthe 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 againstthe hypothesis of the development and modification of species: heseems to lean towards the side of change. The ‘Vestiges of Creation’ appeared in 1844. In the tenth and muchimproved edition (1853) the anonymous author says (p. 155): – ‘Theproposition determined on after much consideration is, that the severalseries of animated beings, from the simplest and oldest up to thehighest 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 oforganisation terminating in the highest dicotyledons and vertebrata,these grades being few in number, and generally marked by intervalsof organic character, which we find to be a practical difficulty inascertaining affinities; second, of another impulse connected with thevital forces, tending, in the course of generations, to modify organicstructures in accordance with external circumstances, as food, thenature of the habitat, and the meteoric agencies, these being the“adaptations” of the natural theologian.’ The author apparently believesthat organisation progresses by sudden leaps, but that the effects
  10. 10. Origin of Species AN HISTORICAL SKETCH 10produced by the conditions of life are gradual. He argues with muchforce on general grounds that species are not immutable productions.But I cannot see how the two supposed ‘impulses’ account in a scientificsense for the numerous and beautiful co-adaptations which we seethroughout nature; I cannot see that we thus gain any insight how, forinstance, a woodpecker has become adapted to its peculiar habits oflife. The work, from its powerful and brilliant style, though displaying inthe earlier editions little accurate knowledge and a great want ofscientific caution, immediately had a very wide circulation. In my opinionit has done excellent service in this country in calling attention to thesubject, in removing prejudice, and in thus preparing the ground for thereception of analogous views. In 1846 the veteran geologist M. J. d’Omalius d’Halloy published inan excellent though short paper (‘Bulletins de l’Acad. Roy Bruxelles,’tom. xiii. p. 581) his opinion that it is more probable that new specieshave been produced by descent with modification than that they havebeen separately created: the author first promulgated this opinion in1831. Professor Owen, in 1849 (‘Nature of Limbs,’ p. 86), wrote as follows:–‘The archetypal idea was manifested in the flesh under diverse suchmodifications, upon this planet, long prior to the existence of thoseanimal species that actually exemplify it. To what natural laws orsecondary causes the orderly succession and progression of suchorganic phenomena may have been committed, we, as yet, areignorant.’ In his Address to the British Association, in 1858, he speaks(p. li.) of ‘the axiom of the continuous operation of creative power, orof the ordained becoming of living things.’ Farther on (p. xc.), afterreferring to geographical distribution, he adds, ‘These phenomenashake our confidence in the conclusion that the Apteryx of New Zealandand the Red Grouse of England were distinct creations in and for thoseislands respectively. Always, also, it may be well to bear in mind thatby the word “creation” the zoologist means “a process he knows notwhat.”’ He amplifies this idea by adding that when such cases as thatof the Red Grouse are ‘enumerated by the zoologists as evidence ofdistinct creation of the bird in and for such islands, he chiefly expresses
  11. 11. Origin of Species AN HISTORICAL SKETCH 11that he knows not how the Red Grouse came to be there, and thereexclusively; signifying also, by this mode of expressing such ignorance,his belief that both the bird and the islands owed their origin to a greatfirst Creative Cause.’ If we interpret these sentences given in the sameAddress, one by the other, it appears that this eminent philosopher feltin 1858 his confidence shaken that the Apteryx and the Red Grousefirst appeared in their respective homes, ‘he knew not how,’ or by someprocess ‘he knew not what.’ This Address was delivered after the papers by Mr Wallace andmyself on the Origin of Species, presently to be referred to, had beenread before the Linnean Society. When the first edition of this work waspublished, I was so completely deceived, as were many others, by suchexpressions as ‘the continuous operation of creative power,’ that Iincluded Professor Owen with other palaeontologists as being firmlyconvinced of the immutability of species; but it appears (‘Anat. ofVertebrates,’ vol. iii. p. 796) that this was on my part a preposterouserror. In the last edition of this work I inferred, and the inference stillseems to me perfectly just, from a passage beginning with the words‘no doubt the type-form,’ &c. (Ibid. vol. i. p. xxxv.), that Professor Owenadmitted that natural selection may have done something in theformation of a new species; but this it appears (Ibid. vol. iii. p. 798) isinaccurate and without evidence. I also gave some extracts from acorrespondence between Professor Owen and the Editor of the‘London Review,’ from which it appeared manifest to the Editor as wellas to myself, that Professor Owen claimed to have promulgated thetheory of natural selection before I had done so; and I expressed mysurprise and satisfaction at this announcement; but as far as it ispossible to understand certain recently published passages (Ibid. vol.iii. p. 798) I have either partially or wholly again fallen into error. It isconsolatory to me that others find Professor Owen’s controversialwritings as difficult to understand and to reconcile with each other, asI do. As far as the mere enunciation of the principle of natural selectionis concerned, it is quite immaterial whether or not Professor Owenpreceded me, for both of us, as shown in this historical sketch, werelong ago preceded by Dr Wells and Mr Matthews.
  12. 12. Origin of Species AN HISTORICAL SKETCH 12 M. Isidore Geoffroy Saint-Hilaire, in his lectures delivered in 1850 (ofwhich a Résumé appeared in the ‘Revue et Mag. de Zoolog.,’ Jan.1851), briefly gives his reason for believing that specific characters‘sont fixés, pour chaque espèce, tant qu’elle se perpétue au milieu desmêmes circonstances: ils se modifient, si les circonstances ambiantesviennent à changer.’ ‘En résumé, l’observation des animaux sauvagesdémontre déjà Ia variabilité limitée des espèces. Les expériences surles animaux sauvages devenus domestiques, et sur les animauxdomestiques redevenus sauvages, la démontrent plus clairementencore. Ces mêmes expériences prouvent, de plus, que les différencesproduites peuvent etre de valeur générique.’ In his ‘Hist. Nat. Générale’(tom. ii. p. 430, 1859) he amplifies analogous conclusions. From a circular lately issued it appears that Dr Freke, in 1851 (‘DublinMedical Press,’ p. 322), propounded the doctrine that all organic beingshave descended from one primordial form. His grounds of belief andtreatment of the subject are wholly different from mine; but as Dr Frekehas now (1861) published his Essay on the ‘Origin of Species by meansof Organic Affinity,’ the difficult attempt to give any idea of his viewswould be superfluous on my part. Mr Herbert Spencer, in an Essay (originally published in the ‘Leader,’March, 1852, and republished in his ‘Essays,’ in 1858), has contrastedthe theories of the Creation and the Development of organic beingswith remarkable skill and force. He argues from the analogy of domesticproductions, from the changes which the embryos of many speciesundergo, from the difficulty of distinguishing species and varieties, andfrom the principle of general gradation, that species have beenmodified; and he attributes the modification to the change ofcircumstances. The author (1855) has also treated Psychology on theprinciple of the necessary acquirement of each mental power andcapacity by gradation. In 1852 M. Naudin, a distinguished botanist, expressly stated, in anadmirable paper on the Origin of Species (‘Revue Horticole, p. 102;since partly republished in the ‘Nouvelles Archives du Muséum,’ tom.i. p.171), his belief that species are formed in an analogous manner asvarieties are under cultivation; and the latter process he attributes to
  13. 13. Origin of Species AN HISTORICAL SKETCH 13man’s power of selection. But he does not show how selection actsunder nature. He believes, like Dean Herbert, that species, whennascent, were more plastic than at present. He lays weight on what hecalls the principle of finality, ‘puissance mystérieuse, indéterminée;fatalité pour les uns; pour les autres, volonté providentielle, dont l’actionincessante sur les êtres vivants détermine, à toutes les époques del’existence du monde, Ia forme, le volume, et la durée de chacun d’eux,en raison de sa destinée dans l’ordre de choses dont il fait partie. C’estcette puissance qui harmonise chaque membre à l’ensemble, enl’appropriant à Ia fonction qu’il doit remplir dans l’organisme général dela nature, fonction qui est pour lui sa raison d’être.’**From references in Bronn’s ‘Untersuchungen über dieEntwickelungs-Gesetze,’ it appears that the celebrated botanist andpalaeontologist Unger published, in 1852, his belief that species undergodevelopment and modification. Dalton, likewise, in Pander and Dalton’s workon Fossil Sloths, expressed, in 1821, a similar belief. Similar views have, as iswell known, been maintained by Oken in his mystical ‘Natur-Philosophie.’ Fromother references in Godron’s work ‘Sur l’Espèce,’ it seems that Bory St Vincent,Burdach, Poiret, and Fries, have all admitted that new species are continuallybeing produced. I may add, that of the thirty-four authors named in this Historical Sketch, whobelieve in the modification of species, or at least disbelieve in separate acts ofcreation, twenty-seven have written on special branches of natural history orgeology. In 1853 a celebrated geologist, Count Keyserling (‘Bulletin de la Soc.Gêolog.,’ 2nd Ser., tom. x. p. 357), suggested that as new diseases,supposed to have been caused by some miasma, have arisen andspread over the world, so at certain periods the germs of existingspecies may have been chemically affected by circumambientmolecules of a particular nature, and thus have given rise to new forms. In this same year,1853, Dr Schaaffhausen published an excellentpamphlet (‘Verhand. des Naturhist. Vereins der Preuss. Rheinlands,’&c.), in which he maintains the development of organic forms on theearth. He infers that many species have kept true for long periods,
  14. 14. Origin of Species AN HISTORICAL SKETCH 14whereas a few have become modified. The distinction of species heexplains by the destruction of intermediate graduated forms. ‘Thusliving plants and animals are not separated from the extinct by newcreations, but are to be regarded as their descendants throughcontinued reproduction.’ A well-known French botanist, M. Lecoq, writes in 1854 (‘Etudes surGéograph. Bot.,’ tom. i. p. 250), ‘On voit que nos recherches sur la fixitéou la variation de l’espèce, nous conduisent directement aux idéesémises, par deux hommes justement célèbres, Geoffroy Saint-Hilaireet Goethe.’ Some other passages scattered through M. Lecoq’s largework, make it a little doubtful how far he extends his views on themodification of species. The ‘Philosophy of Creation’ has been treated in a masterly mannerby the Rev. Baden Powell, in his ‘Essays on the Unity of Worlds,’ 1855.Nothing can be more striking than the manner in which he shows thatthe introduction of new species is ‘a regular, not a casual phenomenon,’or, as Sir John Herschel expresses it, ‘a natural in contradistinction toa miraculous process.’ The third volume of the ‘Journal of the Linnean Society’ containspapers, read July 1st, 1858, by Mr Wallace and myself, in which, asstated in the introductory remarks to this volume, the theory of NaturalSelection is promulgated by Mr Wallace with admirable force andclearness. Von Baer, towards whom all zoologists feel so profound a respect,expressed about the year 1859 (see Prof. Rudolph Wagner, a‘Zoologisch-Anthropologische Untersuchungen,’ 1861, s. 51) hisconviction, chiefly grounded on the laws of geographical distribution,that forms now perfectly distinct have descended from a singleparent-form. In June, 1859, Professor Huxley gave a lecture before the RoyalInstitution on the ‘Persistent Types of Animal Life.’ Referring to suchcases, he remarks, ‘It is difficult to comprehend the meaning of suchfacts as these, if we suppose that each species of animal and plant, oreach great type of organisation, was formed and placed upon thesurface of the globe at long intervals by a distinct act of creative power;
  15. 15. Origin of Species AN HISTORICAL SKETCH 15and it is well to recollect that such an assumption is as unsupported bytradition or revelation as it is opposed to the general analogy of nature.If, on the other hand, we view ‘Persistent Types’ in relation to thathypothesis which supposes the species living at any time to be theresult of the gradual modification of pre-existing species a hypothesiswhich, though unproven, and sadly damaged by some of its supporters,is yet the only one to which physiology lends any countenance; theirexistence would seem to show that the amount of modification whichliving beings have undergone during geological time is but very smallin relation to the whole series of changes which they have suffered.’ In December, 1859, Dr Hooker published his ‘Introduction to theAustralian Flora.’ In the first part of this great work he admits the truthof the descent and modification of species, and supports this doctrineby many original observations. The first edition of this work was published on November 24th, 1859,and the second edition on January 7th, 1860.
  16. 16. Origin of Species INTRODUCTION 16 INTRODUCTION WHEN on board H.M.S. Beagle, as naturalist, I was much struck withcertain facts in the distribution of the inhabitants of South America, andin the geological relations of the present to the past inhabitants of thatcontinent. These facts seemed to me to throw some light on the originof species – that mystery of mysteries, as it has been called by one ofour greatest philosophers. On my return home, it occurred to me, in1837, that something might perhaps be made out on this question bypatiently accumulating and reflecting on all sorts of facts which couldpossibly have any bearing on it. After five years’ work I allowed myselfto speculate on the subject, and drew up some short notes; these Ienlarged in 1844 into a sketch of the conclusions, which then seemedto me probable: from that period to the present day I have steadilypursued the same object. I hope that I may be excused for entering onthese personal details, as I give them to show that I have not beenhasty in coming to a decision. My work is now nearly finished; but as it will take me two or threemore years to complete it, and as my health is far from strong, I havebeen urged to publish this Abstract. I have more especially beeninduced to do this, as Mr Wallace, who is now studying the naturalhistory of the Malay archipelago, has arrived at almost exactly the samegeneral conclusions that I have on the origin of species. Last year hesent to me a memoir on this subject, with a request that I would forwardit to Sir Charles Lyell, who sent it to the Linnean Society, and it ispublished in the third volume of the Journal of that Society. Sir C. Lyelland Dr Hooker, who both knew of my work – the latter having read mysketch of 1844 – honoured me by thinking it advisable to publish, withMr Wallace’s excellent memoir, some brief extracts from mymanuscripts. This Abstract, which I now publish, must necessarily be imperfect. Icannot here give references and authorities for my several statements;and I must trust to the reader reposing some confidence in my accuracy.No doubt errors will have crept in, though I hope I have always beencautious in trusting to good authorities alone. I can here give only the
  17. 17. Origin of Species INTRODUCTION 17general conclusions at which I have arrived, with a few facts inillustration, but which, I hope, in most cases will suffice. No one canfeel more sensible than I do of the necessity of hereafter publishing indetail all the facts, with references, on which my conclusions have beengrounded; and I hope in a future work to do this. For I am well awarethat scarcely a single point is discussed in this volume on which factscannot be adduced, often apparently leading to conclusions directlyopposite to those at which I have arrived. A fair result can be obtainedonly by fully stating and balancing the facts and arguments on bothsides of each question; and this cannot possibly be here done. I much regret that want of space prevents my having the satisfactionof acknowledging the generous assistance which I have received fromvery many naturalists, some of them personally unknown to me. Icannot, however, let this opportunity pass without expressing my deepobligations to Dr Hooker, who for the last fifteen years has aided me inevery possible way by his large stores of knowledge and his excellentjudgement. In considering the Origin of Species, it is quite conceivable that anaturalist, reflecting on the mutual affinities of organic beings, on theirembryological relations, their geographical distribution, geologicalsuccession, and other such facts, might come to the conclusion thateach species had not been independently created, but had descended,like varieties, from other species. Nevertheless, such a conclusion,even if well founded, would be unsatisfactory, until it could be shownhow the innumerable species inhabiting this world have been modified,so as to acquire that perfection of structure and coadaptation whichmost justly excites our admiration. Naturalists continually refer toexternal conditions, such as climate, food, &c., as the only possiblecause of variation. In one very limited sense, as we shall hereafter see,this may be true; but it is preposterous to attribute to mere externalconditions, the structure, for instance, of the woodpecker, with its feet,tail, beak, and tongue, so admirably adapted to catch insects under thebark of trees. In the case of the misseltoe, which draws its nourishmentfrom certain trees, which has seeds that must be transported by certainbirds, and which has flowers with separate sexes absolutely requiring
  18. 18. Origin of Species INTRODUCTION 18the agency of certain insects to bring pollen from one flower to the other,it is equally preposterous to account for the structure of this parasite,with its relations to several distinct organic beings, by the effects ofexternal conditions, or of habit, or of the volition of the plant itself. The author of the ‘Vestiges of Creation’ would, I presume, say that,after a certain unknown number of generations, some bird had givenbirth to a woodpecker, and some plant to the misseltoe, and that thesehad been produced perfect as we now see them; but this assumptionseems to me to be no explanation, for it leaves the case of thecoadaptations of organic beings to each other and to their physicalconditions of life, untouched and unexplained. It is, therefore, of the highest importance to gain a clear insight intothe means of modification and coadaptation. At the commencement ofmy observations it seemed to me probable that a careful study ofdomesticated animals and of cultivated plants would offer the bestchance of making out this obscure problem. Nor have I beendisappointed; in this and in all other perplexing cases I have invariablyfound that our knowledge, imperfect though it be, of variation underdomestication, afforded the best and safest clue. I may venture toexpress my conviction of the high value of such studies, although theyhave been very commonly neglected by naturalists. From these considerations, I shall devote the first chapter of thisAbstract to Variation under Domestication. We shall thus see that alarge amount of hereditary modification is at least possible; and, whatis equally or more important, we shall see how great is the power ofman in accumulating by his Selection successive slight variations. I willthen pass on to the variability of species in a state of nature; but I shall,unfortunately, be compelled to treat this subject far too briefly, as it canbe treated properly only by giving long catalogues of facts. We shall,however, be enabled to discuss what circumstances are mostfavourable to variation. In the next chapter the Struggle for Existenceamongst all organic beings throughout the world, which inevitablyfollows from their high geometrical powers of increase, will be treatedof. This is the doctrine of Malthus, applied to the whole animal andvegetable kingdoms. As many more individuals of each species are
  19. 19. Origin of Species INTRODUCTION 19born than can possibly survive; and as, consequently, there is afrequently recurring struggle for existence, it follows that any being, ifit vary however slightly in any manner profitable to itself, under thecomplex and sometimes varying conditions of life, will have a betterchance of surviving, and thus be naturally selected. From the strongprinciple of inheritance, any selected variety will tend to propagate itsnew and modified form. This fundamental subject of Natural Selection will be treated at somelength in the fourth chapter; and we shall then see how NaturalSelection almost inevitably causes much Extinction of the lessimproved forms of life, and induces what I have called Divergence ofCharacter. In the next chapter I shall discuss the complex and littleknown laws of variation and of correlation of growth. In the foursucceeding chapters, the most apparent and gravest difficulties on thetheory will be given: namely, first, the difficulties of transitions, or inunderstanding how a simple being or a simple organ can be changedand perfected into a highly developed being or elaborately constructedorgan; secondly, the subject of Instinct, or the mental powers ofanimals; thirdly, Hybridism, or the infertility of species and the fertilityof varieties when intercrossed; and fourthly, the imperfection of theGeological Record. In the next chapter I shall consider the geologicalsuccession of organic beings throughout time; in the eleventh andtwelfth, their geographical distribution throughout space; in thethirteenth, their classification or mutual affinities, both when mature andin an embryonic condition. In the last chapter I shall give a briefrecapitulation of the whole work, and a few concluding remarks. No one ought to feel surprise at much remaining as yet unexplainedin regard to the origin of species and varieties, if he makes dueallowance for our profound ignorance in regard to the mutual relationsof all the beings which live around us. Who can explain why one speciesranges widely and is very numerous, and why another allied specieshas a narrow range and is rare? Yet these relations are of the highestimportance, for they determine the present welfare, and, as I believe,the future success and modification of every inhabitant of this world.Still less do we know of the mutual relations of the innumerable
  20. 20. Origin of Species INTRODUCTION 20inhabitants of the world during the many past geological epochs in itshistory. Although much remains obscure, and will long remain obscure,I can entertain no doubt, after the most deliberate study anddispassionate judgement of which I am capable, that the view whichmost naturalists entertain, and which I formerly entertained – namely,that each species has been independently created – is erroneous. I amfully convinced that species are not immutable; but that those belongingto what are called the same genera are lineal descendants of someother and generally extinct species, in the same manner as theacknowledged varieties of any one species are the descendants of thatspecies. Furthermore, I am convinced that Natural Selection has beenthe main but not exclusive means of modification.
  21. 21. Origin of Species VARIATION UNDER DOMESTICATION 21 CHAPTER I VARIATION UNDER DOMESTICATION Causes of Variability – Effects of Habit – Correlation of Growth – Inheritance – Character of Domestic Varieties – Difficulty of distinguishing between Varieties and Species – Origin of Domestic Varieties from one or more Species – Domestic Pigeons, theirDifferences and Origin – Principle of Selection anciently followed, itsEffects – Methodical and Unconscious Selection – Unknown Origin of our Domestic Productions – Circumstances favourable to Man’s power of SelectionWHEN we look to the individuals of the same variety or sub-variety ofour older cultivated plants and animals, one of the first points whichstrikes us, is, that they generally differ much more from each other, thando the individuals of any one species or variety in a state of nature.When we reflect on the vast diversity of the plants and animals whichhave been cultivated, and which have varied during all ages under themost different climates and treatment, I think we are driven to concludethat this greater variability is simply due to our domestic productionshaving been raised under conditions of life not so uniform as, andsomewhat different from, those to which the parent-species have beenexposed under nature. There is, also, I think, some probability in theview propounded by Andrew Knight, that this variability may be partlyconnected with excess of food. It seems pretty clear that organic beingsmust be exposed during several generations to the new conditions oflife to cause any appreciable amount of variation; and that when theorganisation has once begun to vary, it generally continues to vary formany generations. No case is on record of a variable being ceasing tobe variable under cultivation. Our oldest cultivated plants, such aswheat, still often yield new varieties: our oldest domesticated animalsare still capable of rapid improvement or modification. It has been disputed at what period of life the causes of variability,whatever they may be, generally act; whether during the early or late
  22. 22. Origin of Species VARIATION UNDER DOMESTICATION 22period of development of the embryo, or at the instant of conception.Geoffroy St Hilaire’s experiments show that unnatural treatment of theembryo causes monstrosities; and monstrosities cannot be separatedby any clear line of distinction from mere variations. But I am stronglyinclined to suspect that the most frequent cause of variability may beattributed to the male and female reproductive elements having beenaffected prior to the act of conception. Several reasons make mebelieve in this; but the chief one is the remarkable effect whichconfinement or cultivation has on the functions of the reproductivesystem; this system appearing to be far more susceptible than any otherpart of the organization, to the action of any change in the conditionsof life. Nothing is more easy than to tame an animal, and few thingsmore difficult than to get it to breed freely under confinement, even inthe many cases when the male and female unite. How many animalsthere are which will not breed, though living long under not very closeconfinement in their native country! This is generally attributed tovitiated instincts; but how many cultivated plants display the utmostvigour, and yet rarely or never seed! In some few such cases it hasbeen found out that very trifling changes, such as a little more or lesswater at some particular period of growth, will determine whether or notthe plant sets a seed. I cannot here enter on the copious details whichI have collected on this curious subject; but to show how singular thelaws are which determine the reproduction of animals underconfinement, I may just mention that carnivorous animals, even fromthe tropics, breed in this country pretty freely under confinement, withthe exception of the plantigrades or bear family; whereas, carnivorousbirds, with the rarest exceptions, hardly ever lay fertile eggs. Manyexotic plants have pollen utterly worthless, in the same exact conditionas in the most sterile hybrids. When, on the one hand, we seedomesticated animals and plants, though often weak and sickly, yetbreeding quite freely under confinement; and when, on the other hand,we see individuals, though taken young from a state of nature, perfectlytamed, long-lived, and healthy (of which I could give numerousinstances), yet having their reproductive system so seriously affectedby unperceived causes as to fail in acting, we need not be surprised at
  23. 23. Origin of Species VARIATION UNDER DOMESTICATION 23this system, when it does act under confinement, acting not quiteregularly, and producing offspring not perfectly like their parents orvariable. Sterility has been said to be the bane of horticulture; but on this viewwe owe variability to the same cause which produces sterility; andvariability is the source of all the choicest productions of the garden. Imay add, that as some organisms will breed most freely under the mostunnatural conditions (for instance, the rabbit and ferret kept in hutches),showing that their reproductive system has not been thus affected; sowill some animals and plants withstand domestication or cultivation,and vary very slightly – perhaps hardly more than in a state of nature. A long list could easily be given of ‘sporting plants;’ by this termgardeners mean a single bud or offset, which suddenly assumes a newand sometimes very different character from that of the rest of the plant.Such buds can be propagated by grafting, &c., and sometimes by seed.These ‘sports’ are extremely rare under nature, but far from rare undercultivation; and in this case we see that the treatment of the parent hasaffected a bud or offset, and not the ovules or pollen. But it is the opinionof most physiologists that there is no essential difference between abud and an ovule in their earliest stages of formation; so that, in fact,‘sports’ support my view, that variability may be largely attributed to theovules or pollen, or to both, having been affected by the treatment ofthe parent prior to the act of conception. These cases anyhow showthat variation is not necessarily connected, as some authors havesupposed, with the act of generation. Seedlings from the same fruit, and the young of the same litter,sometimes differ considerably from each other, though both the youngand the parents, as Müller has remarked, have apparently beenexposed to exactly the same conditions of life; and this shows howunimportant the direct effects of the conditions of life are in comparisonwith the laws of reproduction, and of growth, and of inheritance; for hadthe action of the conditions been direct, if any of the young had varied,all would probably have varied in the same manner. To judge howmuch, in the case of any variation, we should attribute to the directaction of heat, moisture, light, food, &c., is most difficult: my impression
  24. 24. Origin of Species VARIATION UNDER DOMESTICATION 24is, that with animals such agencies have produced very little directeffect, though apparently more in the case of plants. Under this pointof view, Mr Buckman’s recent experiments on plants seem extremelyvaluable. When all or nearly all the individuals exposed to certainconditions are affected in the same way, the change at first appears tobe directly due to such conditions; but in some cases it can be shownthat quite opposite conditions produce similar changes of structure.Nevertheless some slight amount of change may, I think, be attributedto the direct action of the conditions of life – as, in some cases,increased size from amount of food, colour from particular kinds of foodand from light, and perhaps the thickness of fur from climate. Habit also has a deciding influence, as in the period of flowering withplants when transported from one climate to another. In animals it hasa more marked effect; for instance, I find in the domestic duck that thebones of the wing weigh less and the bones of the leg more, inproportion to the whole skeleton, than do the same bones in thewild-duck; and I presume that this change may be safely attributed tothe domestic duck flying much less, and walking more, than its wildparent. The great and inherited development of the udders in cows andgoats in countries where they are habitually milked, in comparison withthe state of these organs in other countries, is another instance of theeffect of use. Not a single domestic animal can be named which hasnot in some country drooping ears; and the view suggested by someauthors, that the drooping is due to the disuse of the muscles of theear, from the animals not being much alarmed by danger, seemsprobable. There are many laws regulating variation, some few of which can bedimly seen, and will be hereafter briefly mentioned. I will here onlyallude to what may be called correlation of growth. Any change in theembryo or larva will almost certainly entail changes in the matureanimal. In monstrosities, the correlations between quite distinct partsare very curious; and many instances are given in Isidore Geoffroy StHilaire’s great work on this subject. Breeders believe that long limbsare almost always accompanied by an elongated head. Someinstances of correlation are quite whimsical; thus cats with blue eyes
  25. 25. Origin of Species VARIATION UNDER DOMESTICATION 25are invariably deaf; colour and constitutional peculiarities go together,of which many remarkable cases could be given amongst animals andplants. From the facts collected by Heusinger, it appears that whitesheep and pigs are differently affected from coloured individuals bycertain vegetable poisons. Hairless dogs have imperfect teeth;long-haired and coarse-haired animals are apt to have, as is asserted,long or many horns; pigeons with feathered feet have skin betweentheir outer toes; pigeons with short beaks have small feet, and thosewith long beaks large feet. Hence, if man goes on selecting, and thusaugmenting, any peculiarity, he will almost certainly unconsciouslymodify other parts of the structure, owing to the mysterious laws of thecorrelation of growth. The result of the various, quite unknown, or dimly seen laws ofvariation is infinitely complex and diversified. It is well worth whilecarefully to study the several treatises published on some of our oldcultivated plants, as on the hyacinth, potato, even the dahlia, &c.; andit is really surprising to note the endless points in structure andconstitution in which the varieties and sub-varieties differ slightly fromeach other. The whole organization seems to have become plastic, andtends to depart in some small degree from that of the parental type. Any variation which is not inherited is unimportant for us. But thenumber and diversity of inheritable deviations of structure, both thoseof slight and those of considerable physiological importance, is endless.Dr Prosper Lucas’s treatise, in two large volumes, is the fullest and thebest on this subject. No breeder doubts how strong is the tendency toinheritance: like produces like is his fundamental belief: doubts havebeen thrown on this principle by theoretical writers alone. When adeviation appears not unfrequently, and we see it in the father and child,we cannot tell whether it may not be due to the same original causeacting on both; but when amongst individuals, apparently exposed tothe same conditions, any very rare deviation, due to some extraordinarycombination of circumstances, appears in the parent – say, onceamongst several million individuals – and it reappears in the child, themere doctrine of chances almost compels us to attribute itsreappearance to inheritance. Every one must have heard of cases of
  26. 26. Origin of Species VARIATION UNDER DOMESTICATION 26albinism, prickly skin, hairy bodies, &c., appearing in several membersof the same family. If strange and rare deviations of structure are trulyinherited, less strange and commoner deviations may be freelyadmitted to be inheritable. Perhaps the correct way of viewing the wholesubject, would be, to look at the inheritance of every character whateveras the rule, and non-inheritance as the anomaly. The laws governing inheritance are quite unknown; no one can saywhy the same peculiarity in different individuals of the same species,and in individuals of different species, is sometimes inherited andsometimes not so; why the child often reverts in certain characters toits grandfather or grandmother or other much more remote ancestor;why a peculiarity is often transmitted from one sex to both sexes, or toone sex alone, more commonly but not exclusively to the like sex. It isa fact of some little importance to us, that peculiarities appearing in themales of our domestic breeds are often transmitted either exclusively,or in a much greater degree, to males alone. A much more importantrule, which I think may be trusted, is that, at whatever period of life apeculiarity first appears, it tends to appear in the offspring at acorresponding age, though sometimes earlier. In many cases this couldnot be otherwise: thus the inherited peculiarities in the horns of cattlecould appear only in the offspring when nearly mature; peculiarities inthe silkworm are known to appear at the corresponding caterpillar orcocoon stage. But hereditary diseases and some other facts make mebelieve that the rule has a wider extension, and that when there is noapparent reason why a peculiarity should appear at any particular age,yet that it does tend to appear in the offspring at the same period atwhich it first appeared in the parent. I believe this rule to be of thehighest importance in explaining the laws of embryology. Theseremarks are of course confined to the first appearance of the peculiarity,and not to its primary cause, which may have acted on the ovules ormale element; in nearly the same manner as in the crossed offspringfrom a short-horned cow by a long-horned bull, the greater length ofhorn, though appearing late in life, is clearly due to the male element. Having alluded to the subject of reversion, I may here refer to astatement often made by naturalists – namely, that our domestic
  27. 27. Origin of Species VARIATION UNDER DOMESTICATION 27varieties, when run wild, gradually but certainly revert in character totheir aboriginal stocks. Hence it has been argued that no deductionscan be drawn from domestic races to species in a state of nature. Ihave in vain endeavoured to discover on what decisive facts the abovestatement has so often and so boldly been made. There would be greatdifficulty in proving its truth: we may safely conclude that very many ofthe most strongly-marked domestic varieties could not possibly live ina wild state. In many cases we do not know what the aboriginal stockwas, and so could not tell whether or not nearly perfect reversion hadensued. It would be quite necessary, in order to prevent the effects ofintercrossing, that only a single variety should be turned loose in itsnew home. Nevertheless, as our varieties certainly do occasionallyrevert in some of their characters to ancestral forms, it seems to menot improbable, that if we could succeed in naturalising, or were tocultivate, during many generations, the several races, for instance, ofthe cabbage, in very poor soil (in which case, however, some effectwould have to be attributed to the direct action of the poor soil), thatthey would to a large extent, or even wholly, revert to the wild aboriginalstock. Whether or not the experiment would succeed, is not of greatimportance for our line of argument; for by the experiment itself theconditions of life are changed. If it could be shown that our domesticvarieties manifested a strong tendency to reversion, – that is, to losetheir acquired characters, whilst kept under unchanged conditions, andwhilst kept in a considerable body, so that free intercrossing mightcheck, by blending together, any slight deviations of structure, in suchcase, I grant that we could deduce nothing from domestic varieties inregard to species. But there is not a shadow of evidence in favour ofthis view: to assert that we could not breed our cart and race-horses,long and short-horned cattle, and poultry of various breeds, andesculent vegetables, for an almost infinite number of generations,would be opposed to all experience. I may add, that when under naturethe conditions of life do change, variations and reversions of characterprobably do occur; but natural selection, as will hereafter be explained,will determine how far the new characters thus arising shall bepreserved.
  28. 28. Origin of Species VARIATION UNDER DOMESTICATION 28 When we look to the hereditary varieties or races of our domesticanimals and plants, and compare them with species closely alliedtogether, we generally perceive in each domestic race, as alreadyremarked, less uniformity of character than in true species. Domesticraces of the same species, also, often have a somewhat monstrouscharacter; by which I mean, that, although differing from each other,and from the other species of the same genus, in several triflingrespects, they often differ in an extreme degree in some one part, bothwhen compared one with another, and more especially when comparedwith all the species in nature to which they are nearest allied. With theseexceptions (and with that of the perfect fertility of varieties whencrossed, – a subject hereafter to be discussed), domestic races of thesame species differ from each other in the same manner as, only inmost cases in a lesser degree than, do closely-allied species of thesame genus in a state of nature. I think this must be admitted, whenwe find that there are hardly any domestic races, either amongstanimals or plants, which have not been ranked by some competentjudges as mere varieties, and by other competent judges as thedescendants of aboriginally distinct species. If any marked distinctionexisted between domestic races and species, this source of doubt couldnot so perpetually recur. It has often been stated that domestic racesdo not differ from each other in characters of generic value. I think itcould be shown that this statement is hardly correct; but naturalistsdiffer most widely in determining what characters are of generic value;all such valuations being at present empirical. Moreover, on the viewof the origin of genera which I shall presently give, we have no right toexpect often to meet with generic differences in our domesticatedproductions. When we attempt to estimate the amount of structural differencebetween the domestic races of the same species, we are soon involvedin doubt, from not knowing whether they have descended from one orseveral parent-species. This point, if it could be cleared up, would beinteresting; if, for instance, it could be shown that the greyhound,bloodhound, terrier, spaniel, and bull-dog, which we all know propagatetheir kind so truly, were the offspring of any single species, then such
  29. 29. Origin of Species VARIATION UNDER DOMESTICATION 29facts would have great weight in making us doubt about the immutabilityof the many very closely allied and natural species – for instance, ofthe many foxes – inhabiting different quarters of the world. I do notbelieve, as we shall presently see, that all our dogs have descendedfrom any one wild species; but, in the case of some other domesticraces, there is presumptive, or even strong, evidence in favour of thisview. It has often been assumed that man has chosen for domesticationanimals and plants having an extraordinary inherent tendency to vary,and likewise to withstand diverse climates. I do not dispute that thesecapacities have added largely to the value of most of our domesticatedproductions; but how could a savage possibly know, when he firsttamed an animal, whether it would vary in succeeding generations, andwhether it would endure other climates? Has the little variability of theass or guinea-fowl, or the small power of endurance of warmth by thereindeer, or of cold by the common camel, prevented theirdomestication? I cannot doubt that if other animals and plants, equalin number to our domesticated productions, and belonging to equallydiverse classes and countries, were taken from a state of nature, andcould be made to breed for an equal number of generations underdomestication, they would vary on an average as largely as the parentspecies of our existing domesticated productions have varied. In the case of most of our anciently domesticated animals and plants,I do not think it is possible to come to any definite conclusion, whetherthey have descended from one or several species. The argumentmainly relied on by those who believe in the multiple origin of ourdomestic animals is, that we find in the most ancient records, moreespecially on the monuments of Egypt, much diversity in the breeds;and that some of the breeds closely resemble, perhaps are identicalwith, those still existing. Even if this latter fact were found more strictlyand generally true than seems to me to be the case, what does it show,but that some of our breeds originated there, four or five thousand yearsago? But Mr Horner’s researches have rendered it in some degreeprobable that man sufficiently civilized to have manufactured potteryexisted in the valley of the Nile thirteen or fourteen thousand years ago;
  30. 30. Origin of Species VARIATION UNDER DOMESTICATION 30and who will pretend to say how long before these ancient periods,savages, like those of Tierra del Fuego or Australia, who possess asemi-domestic dog, may not have existed in Egypt? The whole subject must, I think, remain vague; nevertheless, I may,without here entering on any details, state that, from geographical andother considerations, I think it highly probable that our domestic dogshave descended from several wild species. In regard to sheep andgoats I can form no opinion. I should think, from facts communicatedto me by Mr Blyth, on the habits, voice, and constitution, &c., of thehumped Indian cattle, that these had descended from a differentaboriginal stock from our European cattle; and several competentjudges believe that these latter have had more than one wild parent.With respect to horses, from reasons which I cannot give here, I amdoubtfully inclined to believe, in opposition to several authors, that allthe races have descended from one wild stock. Mr Blyth, whoseopinion, from his large and varied stores of knowledge, I should valuemore than that of almost any one, thinks that all the breeds of poultryhave proceeded from the common wild Indian fowl (Gallus bankiva). Inregard to ducks and rabbits, the breeds of which differ considerablyfrom each other in structure, I do not doubt that they all have descendedfrom the common wild duck and rabbit. The doctrine of the origin of our several domestic races from severalaboriginal stocks, has been carried to an absurd extreme by someauthors. They believe that every race which breeds true, let thedistinctive characters be ever so slight, has had its wild prototype. Atthis rate there must have existed at least a score of species of wildcattle, as many sheep, and several goats in Europe alone, and severaleven within Great Britain. One author believes that there formerlyexisted in Great Britain eleven wild species of sheep peculiar to it! Whenwe bear in mind that Britain has now hardly one peculiar mammal, andFrance but few distinct from those of Germany and conversely, and sowith Hungary, Spain, &c., but that each of these kingdoms possessesseveral peculiar breeds of cattle, sheep, &c., we must admit that manydomestic breeds have originated in Europe; for whence could they havebeen derived, as these several countries do not possess a number of
  31. 31. Origin of Species VARIATION UNDER DOMESTICATION 31peculiar species as distinct parent-stocks? So it is in India. Even in thecase of the domestic dogs of the whole world, which I fully admit haveprobably descended from several wild species, I cannot doubt thatthere has been an immense amount of inherited variation. Who canbelieve that animals closely resembling the Italian greyhound, thebloodhound, the bull-dog, or Blenheim spaniel, &c. – so unlike all wildCanidae – ever existed freely in a state of nature? It has often beenloosely said that all our races of dogs have been produced by thecrossing of a few aboriginal species; but by crossing we can get onlyforms in some degree intermediate between their parents; and if weaccount for our several domestic races by this process, we must admitthe former existence of the most extreme forms, as the Italiangreyhound, bloodhound, bull-dog, &c., in the wild state. Moreover, thepossibility of making distinct races by crossing has been greatlyexaggerated. There can be no doubt that a race may be modified byoccasional crosses, if aided by the careful selection of those individualmongrels, which present any desired character; but that a race couldbe obtained nearly intermediate between two extremely different racesor species, I can hardly believe. Sir J. Sebright expresslyexperimentised for this object, and failed. The offspring from the firstcross between two pure breeds is tolerably and sometimes (as I havefound with pigeons) extremely uniform, and everything seems simpleenough; but when these mongrels are crossed one with another forseveral generations, hardly two of them will be alike, and then theextreme difficulty, or rather utter hopelessness, of the task becomesapparent. Certainly, a breed intermediate between two very distinctbreeds could not be got without extreme care and long-continuedselection; nor can I find a single case on record of a permanent racehaving been thus formed. On the Breeds of the Domestic Pigeon. Believing that it is alwaysbest to study some special group, I have, after deliberation, taken updomestic pigeons. I have kept every breed which I could purchase orobtain, and have been most kindly favoured with skins from severalquarters of the world, more especially by the Hon. W. Elliot from India,
  32. 32. Origin of Species VARIATION UNDER DOMESTICATION 32and by the Hon. C. Murray from Persia. Many treatises in differentlanguages have been published on pigeons, and some of them arevery important, as being of considerable antiquity. I have associatedwith several eminent fanciers, and have been permitted to join two ofthe London Pigeon Clubs. The diversity of the breeds is somethingastonishing. Compare the English carrier and the short-faced tumbler,and see the wonderful difference in their beaks, entailing correspondingdifferences in their skulls. The carrier, more especially the male bird, isalso remarkable from the wonderful development of the carunculatedskin about the head, and this is accompanied by greatly elongatedeyelids, very large external orifices to the nostrils, and a wide gape ofmouth. The short-faced tumbler has a beak in outline almost like thatof a finch; and the common tumbler has the singular and strictlyinherited habit of flying at a great height in a compact flock, and tumblingin the air head over heels. The runt is a bird of great size, with long,massive beak and large feet; some of the sub-breeds of runts havevery long necks, others very long wings and tails, others singularly shorttails. The barb is allied to the carrier, but, instead of a very long beak,has a very short and very broad one. The pouter has a much elongatedbody, wings, and legs; and its enormously developed crop, which itglories in inflating, may well excite astonishment and even laughter.The turbit has a very short and conical beak, with a line of reversedfeathers down the breast; and it has the habit of continually expandingslightly the upper part of the oesophagus. The Jacobin has the feathersso much reversed along the back of the neck that they form a hood,and it has, proportionally to its size, much elongated wing and tailfeathers. The trumpeter and laugher, as their names express, utter avery different coo from the other breeds. The fantail has thirty or evenforty tail-feathers, instead of twelve or fourteen, the normal number inall members of the great pigeon family; and these feathers are keptexpanded, and are carried so erect that in good birds the head and tailtouch; the oil-gland is quite aborted. Several other less distinct breedsmight have been specified. In the skeletons of the several breeds, the development of the bonesof the face in length and breadth and curvature differs enormously. The
  33. 33. Origin of Species VARIATION UNDER DOMESTICATION 33shape, as well as the breadth and length of the ramus of the lower jaw,varies in a highly remarkable manner. The number of the caudal andsacral vertebrae vary; as does the number of the ribs, together withtheir relative breadth and the presence of processes. The size andshape of the apertures in the sternum are highly variable; so is thedegree of divergence and relative size of the two arms of the furcula.The proportional width of the gape of mouth, the proportional length ofthe eye-lids, of the orifice of the nostrils, of the tongue (not always instrict correlation with the length of beak), the size of the crop and of theupper part of the oesophagus; the development and abortion of theoil-gland; the number of the primary wing and caudal feathers; therelative length of wing and tail to each other and to the body; the relativelength of leg and of the feet; the number of scutellae on the toes, thedevelopment of skin between the toes, are all points of structure whichare variable. The period at which the perfect plumage is acquiredvaries, as does the state of the down with which the nestling birds areclothed when hatched. The shape and size of the eggs vary. Themanner of flight differs remarkably; as does in some breeds the voiceand disposition. Lastly, in certain breeds, the males and females havecome to differ to a slight degree from each other. Altogether at least a score of pigeons might be chosen, which ifshown to an ornithologist, and he were told that they were wild birds,would certainly, I think, be ranked by him as well-defined species.Moreover, I do not believe that any ornithologist would place the Englishcarrier, the short-faced tumbler, the runt, the barb, pouter, and fantailin the same genus; more especially as in each of these breeds severaltruly-inherited sub-breeds, or species as he might have called them,could be shown him. Great as the differences are between the breeds of pigeons, I amfully convinced that the common opinion of naturalists is correct,namely, that all have descended from the rock-pigeon (Columba livia),including under this term several geographical races or sub-species,which differ from each other in the most trifling respects. As several ofthe reasons which have led me to this belief are in some degreeapplicable in other cases, I will here briefly give them. If the several
  34. 34. Origin of Species VARIATION UNDER DOMESTICATION 34breeds are not varieties, and have not proceeded from the rock-pigeon,they must have descended from at least seven or eight aboriginalstocks; for it is impossible to make the present domestic breeds by thecrossing of any lesser number: how, for instance, could a pouter beproduced by crossing two breeds unless one of the parent-stockspossessed the characteristic enormous crop? The supposed aboriginalstocks must all have been rock-pigeons, that is, not breeding or willinglyperching on trees. But besides C. livia, with its geographicalsub-species, only two or three other species of rock-pigeons are known;and these have not any of the characters of the domestic breeds. Hencethe supposed aboriginal stocks must either still exist in the countrieswhere they were originally domesticated, and yet be unknown toornithologists; and this, considering their size, habits, and remarkablecharacters, seems very improbable; or they must have become extinctin the wild state. But birds breeding on precipices, and good fliers, areunlikely to be exterminated; and the common rock-pigeon, which hasthe same habits with the domestic breeds, has not been exterminatedeven on several of the smaller British islets, or on the shores of theMediterranean. Hence the supposed extermination of so many specieshaving similar habits with the rock-pigeon seems to me a very rashassumption. Moreover, the several above-named domesticated breedshave been transported to all parts of the world, and, therefore, someof them must have been carried back again into their native country;but not one has ever become wild or feral, though the dovecot-pigeon,which is the rock-pigeon in a very slightly altered state, has becomeferal in several places. Again, all recent experience shows that it is mostdifficult to get any wild animal to breed freely under domestication; yeton the hypothesis of the multiple origin of our pigeons, it must beassumed that at least seven or eight species were so thoroughlydomesticated in ancient times by half-civilized man, as to be quiteprolific under confinement. An argument, as it seems to me, of great weight, and applicable inseveral other cases, is, that the above-specified breeds, thoughagreeing generally in constitution, habits, voice, colouring, and in mostparts of their structure, with the wild rock-pigeon, yet are certainly highly
  35. 35. Origin of Species VARIATION UNDER DOMESTICATION 35abnormal in other parts of their structure: we may look in vainthroughout the whole great family of Columbidae for a beak like that ofthe English carrier, or that of the short-faced tumbler, or barb; forreversed feathers like those of the Jacobin; for a crop like that of thepouter; for tail-feathers like those of the fantail. Hence it must beassumed not only that half-civilized man succeeded in thoroughlydomesticating several species, but that he intentionally or by chancepicked out extraordinarily abnormal species; and further, that thesevery species have since all become extinct or unknown. So manystrange contingencies seem to me improbable in the highest degree. Some facts in regard to the colouring of pigeons well deserveconsideration. The rock-pigeon is of a slaty-blue, and has a white rump(the Indian sub-species, C. intermedia of Strickland, having it bluish);the tail has a terminal dark bar, with the bases of the outer feathersexternally edged with white; the wings have two black bars; somesemi-domestic breeds and some apparently truly wild breeds have,besides the two black bars, the wings chequered with black. Theseseveral marks do not occur together in any other species of the wholefamily. Now, in every one of the domestic breeds, taking thoroughlywell-bred birds, all the above marks, even to the white edging of theouter tail-feathers, sometimes concur perfectly developed. Moreover,when two birds belonging to two distinct breeds are crossed, neither ofwhich is blue or has any of the above-specified marks, the mongreloffspring are very apt suddenly to acquire these characters; forinstance, I crossed some uniformly white fantails with some uniformlyblack barbs, and they produced mottled brown and black birds; theseI again crossed together, and one grandchild of the pure white fantailand pure black barb was of as beautiful a blue colour, with the whiterump, double black wing-bar, and barred and white-edged tail-feathers,as any wild rock-pigeon! We can understand these facts, on thewell-known principle of reversion to ancestral characters, if all thedomestic breeds have descended from the rock-pigeon. But if we denythis, we must make one of the two following highly improbablesuppositions. Either, firstly, that all the several imagined aboriginalstocks were coloured and marked like the rock-pigeon, although no
  36. 36. Origin of Species VARIATION UNDER DOMESTICATION 36other existing species is thus coloured and marked, so that in eachseparate breed there might be a tendency to revert to the very samecolours and markings. Or, secondly, that each breed, even the purest,has within a dozen or, at most, within a score of generations, beencrossed by the rock-pigeon: I say within a dozen or twenty generations,for we know of no fact countenancing the belief that the child everreverts to some one ancestor, removed by a greater number ofgenerations. In a breed which has been crossed only once with somedistinct breed, the tendency to reversion to any character derived fromsuch cross will naturally become less and less, as in each succeedinggeneration there will be less of the foreign blood; but when there hasbeen no cross with a distinct breed, and there is a tendency in bothparents to revert to a character, which has been lost during some formergeneration, this tendency, for all that we can see to the contrary, maybe transmitted undiminished for an indefinite number of generations.These two distinct cases are often confounded in treatises oninheritance. Lastly, the hybrids or mongrels from between all the domestic breedsof pigeons are perfectly fertile. I can state this from my ownobservations, purposely made on the most distinct breeds. Now, it isdifficult, perhaps impossible, to bring forward one case of the hybridoffspring of two animals clearly distinct being themselves perfectlyfertile. Some authors believe that long-continued domesticationeliminates this strong tendency to sterility: from the history of the dog Ithink there is some probability in this hypothesis, if applied to speciesclosely related together, though it is unsupported by a singleexperiment. But to extend the hypothesis so far as to suppose thatspecies, aboriginally as distinct as carriers, tumblers, pouters, andfantails now are, should yield offspring perfectly fertile, inter se, seemsto me rash in the extreme. From these several reasons, namely, the improbability of man havingformerly got seven or eight supposed species of pigeons to breed freelyunder domestication; these supposed species being quite unknown ina wild state, and their becoming nowhere feral; these species havingvery abnormal characters in certain respects, as compared with all
  37. 37. Origin of Species VARIATION UNDER DOMESTICATION 37other Columbidae, though so like in most other respects to therock-pigeon; the blue colour and various marks occasionally appearingin all the breeds, both when kept pure and when crossed; the mongreloffspring being perfectly fertile; – from these several reasons, takentogether, I can feel no doubt that all our domestic breeds havedescended from the Columba livia with its geographical sub-species. In favour of this view, I may add, firstly, that C. livia, or therock-pigeon, has been found capable of domestication in Europe andin India; and that it agrees in habits and in a great number of points ofstructure with all the domestic breeds. Secondly, although an Englishcarrier or short-faced tumbler differs immensely in certain charactersfrom the rock-pigeon, yet by comparing the several sub-breeds of thesebreeds, more especially those brought from distant countries, we canmake an almost perfect series between the extremes of structure.Thirdly, those characters which are mainly distinctive of each breed,for instance the wattle and length of beak of the carrier, the shortnessof that of the tumbler, and the number of tail-feathers in the fantail, arein each breed eminently variable; and the explanation of this fact willbe obvious when we come to treat of selection. Fourthly, pigeons havebeen watched, and tended with the utmost care, and loved by manypeople. They have been domesticated for thousands of years in severalquarters of the world; the earliest known record of pigeons is in the fifthEgyptian dynasty, about 3000 B.C., as was pointed out to me byProfessor Lepsius; but Mr Birch informs me that pigeons are given ina bill of fare in the previous dynasty. In the time of the Romans, as wehear from Pliny, immense prices were given for pigeons; ‘nay, they arecome to this pass, that they can reckon up their pedigree and race.’Pigeons were much valued by Akber Khan in India, about the year1600; never less than 20,000 pigeons were taken with the court. ‘Themonarchs of Iran and Turan sent him some very rare birds;’ and,continues the courtly historian, ‘His Majesty by crossing the breeds,which method was never practised before, has improved themastonishingly.’ About this same period the Dutch were as eager aboutpigeons as were the old Romans. The paramount importance of theseconsiderations in explaining the immense amount of variation which
  38. 38. Origin of Species VARIATION UNDER DOMESTICATION 38pigeons have undergone, will be obvious when we treat of Selection.We shall then, also, see how it is that the breeds so often have asomewhat monstrous character. It is also a most favourablecircumstance for the production of distinct breeds, that male and femalepigeons can be easily mated for life; and thus different breeds can bekept together in the same aviary. I have discussed the probable origin of domestic pigeons at some,yet quite insufficient, length; because when I first kept pigeons andwatched the several kinds, knowing well how true they bred, I felt fullyas much difficulty in believing that they could ever have descendedfrom a common parent, as any naturalist could in coming to a similarconclusion in regard to the many species of finches, or other largegroups of birds, in nature. One circumstance has struck me much;namely, that all the breeders of the various domestic animals and thecultivators of plants, with whom I have ever conversed, or whosetreatises I have read, are firmly convinced that the several breeds towhich each has attended, are descended from so many aboriginallydistinct species. Ask, as I have asked, a celebrated raiser of Herefordcattle, whether his cattle might not have descended from longhorns,and he will laugh you to scorn. I have never met a pigeon, or poultry,or duck, or rabbit fancier, who was not fully convinced that each mainbreed was descended from a distinct species. Van Mons, in his treatiseon pears and apples, shows how utterly he disbelieves that the severalsorts, for instance a Ribston-pippin or Codlin-apple, could ever haveproceeded from the seeds of the same tree. Innumerable otherexamples could be given. The explanation, I think, is simple: fromlong-continued study they are strongly impressed with the differencesbetween the several races; and though they well know that each racevaries slightly, for they win their prizes by selecting such slightdifferences, yet they ignore all general arguments, and refuse to sumup in their minds slight differences accumulated during manysuccessive generations. May not those naturalists who, knowing farless of the laws of inheritance than does the breeder, and knowing nomore than he does of the intermediate links in the long lines of descent,yet admit that many of our domestic races have descended from the
  39. 39. Origin of Species VARIATION UNDER DOMESTICATION 39same parents – may they not learn a lesson of caution, when theyderide the idea of species in a state of nature being lineal descendantsof other species? Selection. Let us now briefly consider the steps by which domesticraces have been produced, either from one or from several alliedspecies. Some little effect may, perhaps, be attributed to the directaction of the external conditions of life, and some little to habit; but hewould be a bold man who would account by such agencies for thedifferences of a dray and race horse, a greyhound and bloodhound, acarrier and tumbler pigeon. One of the most remarkable features in ourdomesticated races is that we see in them adaptation, not indeed tothe animal’s or plant’s own good, but to man’s use or fancy. Somevariations useful to him have probably arisen suddenly, or by one step;many botanists, for instance, believe that the fuller’s teazle, with itshooks, which cannot be rivalled by any mechanical contrivance, is onlya variety of the wild Dipsacus; and this amount of change may havesuddenly arisen in a seedling. So it has probably been with the turnspitdog; and this is known to have been the case with the ancon sheep.But when we compare the dray-horse and race-horse, the dromedaryand camel, the various breeds of sheep fitted either for cultivated landor mountain pasture, with the wool of one breed good for one purpose,and that of another breed for another purpose; when we compare themany breeds of dogs, each good for man in very different ways; whenwe compare the game-cock, so pertinacious in battle, with other breedsso little quarrelsome, with ‘everlasting layers’ which never desire to sit,and with the bantam so small and elegant; when we compare the hostof agricultural, culinary, orchard, and flower-garden races of plants,most useful to man at different seasons and for different purposes, orso beautiful in his eyes, we must, I think, look further than to merevariability. We cannot suppose that all the breeds were suddenlyproduced as perfect and as useful as we now see them; indeed, inseveral cases, we know that this has not been their history. The key isman’s power of accumulative selection: nature gives successivevariations; man adds them up in certain directions useful to him. In this
  40. 40. Origin of Species VARIATION UNDER DOMESTICATION 40sense he may be said to make for himself useful breeds. The great power of this principle of selection is not hypothetical. It iscertain that several of our eminent breeders have, even within a singlelifetime, modified to a large extent some breeds of cattle and sheep. Inorder fully to realize what they have done, it is almost necessary to readseveral of the many treatises devoted to this subject, and to inspect theanimals. Breeders habitually speak of an animal’s organisation assomething quite plastic, which they can model almost as they please.If I had space I could quote numerous passages to this effect fromhighly competent authorities. Youatt, who was probably betteracquainted with the works of agriculturalists than almost any otherindividual, and who was himself a very good judge of an animal, speaksof the principle of selection as ‘that which enables the agriculturist, notonly to modify the character of his flock, but to change it altogether. Itis the magician’s wand, by means of which he may summon into lifewhatever form and mould he pleases.’ Lord Somerville, speaking ofwhat breeders have done for sheep, says: – ‘It would seem as if theyhad chalked out upon a wall a form perfect in itself, and then had givenit existence. ‘That most skilful breeder, Sir John Sebright, used to say,with respect to pigeons, that ‘he would produce any given feather inthree years, but it would take him six years to obtain head and beak.’In Saxony the importance of the principle of selection in regard tomerino sheep is so fully recognised, that men follow it as a trade: thesheep are placed on a table and are studied, like a picture by aconnoisseur; this is done three times at intervals of months, and thesheep are each time marked and classed, so that the very best mayultimately be selected for breeding. What English breeders have actually effected is proved by theenormous prices given for animals with a good pedigree; and thesehave now been exported to almost every quarter of the world. Theimprovement is by no means generally due to crossing different breeds;all the best breeders are strongly opposed to this practice, exceptsometimes amongst closely allied sub-breeds. And when a cross hasbeen made, the closest selection is far more indispensable even thanin ordinary cases. If selection consisted merely in separating some very
  41. 41. Origin of Species VARIATION UNDER DOMESTICATION 41distinct variety, and breeding from it, the principle would be so obviousas hardly to be worth notice; but its importance consists in the greateffect produced by the accumulation in one direction, during successivegenerations, of differences absolutely inappreciable by an uneducatedeye – differences which I for one have vainly attempted to appreciate.Not one man in a thousand has accuracy of eye and judgementsufficient to become an eminent breeder. If gifted with these qualities,and he studies his subject for years, and devotes his lifetime to it withindomitable perseverance, he will succeed, and may make greatimprovements; if he wants any of these qualities, he will assuredly fail.Few would readily believe in the natural capacity and years of practicerequisite to become even a skilful pigeon-fancier. The same principles are followed by horticulturists; but the variationsare here often more abrupt. No one supposes that our choicestproductions have been produced by a single variation from theaboriginal stock. We have proofs that this is not so in some cases, inwhich exact records have been kept; thus, to give a very triflinginstance, the steadily-increasing size of the common gooseberry maybe quoted. We see an astonishing improvement in many florists’flowers, when the flowers of the present day are compared withdrawings made only twenty or thirty years ago. When a race of plantsis once pretty well established, the seed-raisers do not pick out the bestplants, but merely go over their seed-beds, and pull up the ‘rogues,’ asthey call the plants that deviate from the proper standard. With animalsthis kind of selection is, in fact, also followed; for hardly any one is socareless as to allow his worst animals to breed. In regard to plants, there is another means of observing theaccumulated effects of selection – namely, by comparing the diversityof flowers in the different varieties of the same species in theflower-garden; the diversity of leaves, pods, or tubers, or whatever partis valued, in the kitchen-garden, in comparison with the flowers of thesame varieties; and the diversity of fruit of the same species in theorchard, in comparison with the leaves and flowers of the same set ofvarieties. See how different the leaves of the cabbage are, and howextremely alike the flowers; how unlike the flowers of the heartsease
  42. 42. Origin of Species VARIATION UNDER DOMESTICATION 42are, and how alike the leaves; how much the fruit of the different kindsof gooseberries differ in size, colour, shape, and hairiness, and yet theflowers present very slight differences. It is not that the varieties whichdiffer largely in some one point do not differ at all in other points; thisis hardly ever, perhaps never, the case. The laws of correlation ofgrowth, the importance of which should never be overlooked, willensure some differences; but, as a general rule, I cannot doubt that thecontinued selection of slight variations, either in the leaves, the flowers,or the fruit, will produce races differing from each other chiefly in thesecharacters. It may be objected that the principle of selection has been reducedto methodical practice for scarcely more than three-quarters of acentury; it has certainly been more attended to of late years, and manytreatises have been published on the subject; and the result, I may add,has been, in a corresponding degree, rapid and important. But it is veryfar from true that the principle is a modern discovery. I could giveseveral references to the full acknowledgement of the importance ofthe principle in works of high antiquity. In rude and barbarous periodsof English history choice animals were often imported, and laws werepassed to prevent their exportation: the destruction of horses under acertain size was ordered, and this may be compared to the ‘roguing’ ofplants by nurserymen. The principle of selection I find distinctly givenin an ancient Chinese encyclopaedia. Explicit rules are laid down bysome of the Roman classical writers. From passages in Genesis, it isclear that the colour of domestic animals was at that early periodattended to. Savages now sometimes cross their dogs with wild canineanimals, to improve the breed, and they formerly did so, as is attestedby passages in Pliny. The savages in South Africa match their draughtcattle by colour, as do some of the Esquimaux their teams of dogs.Livingstone shows how much good domestic breeds are valued by thenegroes of the interior of Africa who have not associated withEuropeans. Some of these facts do not show actual selection, but theyshow that the breeding of domestic animals was carefully attended toin ancient times, and is now attended to by the lowest savages. It would,indeed, have been a strange fact, had attention not been paid to
  43. 43. Origin of Species VARIATION UNDER DOMESTICATION 43breeding, for the inheritance of good and bad qualities is so obvious. At the present time, eminent breeders try by methodical selection,with a distinct object in view, to make a new strain or sub-breed,superior to anything existing in the country. But, for our purpose, a kindof Selection, which may be called Unconscious, and which results fromevery one trying to possess and breed from the best individual animals,is more important. Thus, a man who intends keeping pointers naturallytries to get as good dogs as he can, and afterwards breeds from hisown best dogs, but he has no wish or expectation of permanentlyaltering the breed. Nevertheless I cannot doubt that this process,continued during centuries, would improve and modify any breed, inthe same way as Bakewell, Collins, &c., by this very same process,only carried on more methodically, did greatly modify, even during theirown lifetimes, the forms and qualities of their cattle. Slow and insensiblechanges of this kind could never be recognised unless actualmeasurements or careful drawings of the breeds in question had beenmade long ago, which might serve for comparison. In some cases,however, unchanged or but little changed individuals of the same breedmay be found in less civilised districts, where the breed has been lessimproved. There is reason to believe that King Charles’s spaniel hasbeen unconsciously modified to a large extent since the time of thatmonarch. Some highly competent authorities are convinced that thesetter is directly derived from the spaniel, and has probably been slowlyaltered from it. It is known that the English pointer has been greatlychanged within the last century, and in this case the change has, it isbelieved, been chiefly effected by crosses with the fox-hound; but whatconcerns us is, that the change has been effected unconsciously andgradually, and yet so effectually, that, though the old Spanish pointercertainly came from Spain, Mr Barrow has not seen, as I am informedby him, any native dog in Spain like our pointer. By a similar process of selection, and by careful training, the wholebody of English racehorses have come to surpass in fleetness and sizethe parent Arab stock, so that the latter, by the regulations for theGoodwood Races, are favoured in the weights they carry. Lord Spencerand others have shown how the cattle of England have increased in
  44. 44. Origin of Species VARIATION UNDER DOMESTICATION 44weight and in early maturity, compared with the stock formerly kept inthis country. By comparing the accounts given in old pigeon treatisesof carriers and tumblers with these breeds as now existing in Britain,India, and Persia, we can, I think, clearly trace the stages through whichthey have insensibly passed, and come to differ so greatly from therock-pigeon. Youatt gives an excellent illustration of the effects of a course ofselection, which may be considered as unconsciously followed, in sofar that the breeders could never have expected or even have wishedto have produced the result which ensued – namely, the production oftwo distinct strains. The two flocks of Leicester sheep kept by MrBuckley and Mr Burgess, as Mr Youatt remarks, ‘have been purely bredfrom the original stock of Mr Bakewell for upwards of fifty years. Thereis not a suspicion existing in the mind of any one at all acquainted withthe subject that the owner of either of them has deviated in any oneinstance from the pure blood of Mr Bakewell’s flock, and yet thedifference between the sheep possessed by these two gentlemen isso great that they have the appearance of being quite differentvarieties.’ If there exist savages so barbarous as never to think of the inheritedcharacter of the offspring of their domestic animals, yet any one animalparticularly useful to them, for any special purpose, would be carefullypreserved during famines and other accidents, to which savages areso liable, and such choice animals would thus generally leave moreoffspring than the inferior ones; so that in this case there would be akind of unconscious selection going on. We see the value set onanimals even by the barbarians of Tierra del Fuego, by their killing anddevouring their old women, in times of dearth, as of less value thantheir dogs. In plants the same gradual process of improvement, through theoccasional preservation of the best individuals, whether or notsufficiently distinct to be ranked at their first appearance as distinctvarieties, and whether or not two or more species or races have becomeblended together by crossing, may plainly be recognised in theincreased size and beauty which we now see in the varieties of the