The Project Gutenberg EBook of On the Origin of Species by Means of Natural Selection, by Charles docx

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The Project Gutenberg EBook of On theOrigin of Species by Means of

Natural Selection, by Charles Darwin

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Title: On the Origin of Species by Meansof Natural Selection

or the Preservation of Favoured Races inthe Struggle for

Life (2nd edition)Author: Charles Darwin

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Language: English*** START OF THIS PROJECT GUTENBERG EBOOKORIGIN OF SPECIES ***Produced by Steven Gibbs, Keith Edkins andthe OnlineDistributed Proofreading Team athttp://www.pgdp.netTranscriber'snote:

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marked passage.

ON THE

ORIGIN OFSPECIES.

"But with regard to the material world, wecan at least go so far as this—we canperceive that events are brought about notby insulated interpositions of Divinepower, exerted in each particular case, butby the establishment of general laws."

Whewell: Bridgewater Treatise.

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'natural' is stated, fixed, or settled; since

what is natural as much requires andpresupposes an intelligent agent to render

it so, i.e to effect it continually or at

stated times, as what is supernatural ormiraculous does to effect it for once."

Butler: Analogy of Revealed Religion.

"To conclude, therefore, let no man out ofa weak conceit of sobriety, or an ill-applied moderation, think or maintain, thata man can search too far or be too wellstudied in the book of God's word, or inthe book of God's works; divinity orphilosophy; but rather let men endeavouran endless progress or proficience inboth."

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Down, Bromley, Kent,

October 1st, 1859 (1st Thousand).

ON

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By CHARLESDARWIN, M.A.,

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JOHN MURRAY,ALBEMARLE STREET.

1860.

The right of Translation is reserved.

LONDON: PRINTED BY W CLOWESAND SONS, STAMFORD STREET,

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CONTENTS.

Introduction

Page 1

CHAPTER I.

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being very closely, but unequally, relatedto each other, and in having restrictedranges

44-59

CHAPTER III.

Struggle for Existence.

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of the same species; often severe betweenspecies of the same genus—The relationof organism to organism the mostimportant of all relations

60-79

CHAPTER IV.

Natural Selection.

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individuals—Slow action—Extinctioncaused by Natural Selection—Divergenceof Character, related to the diversity ofinhabitants of any small area, and tonaturalisation—Action of NaturalSelection, through Divergence ofCharacter and Extinction, on thedescendants from a common parent—Explains the Grouping of all organicbeings

80-130

CHAPTER V.

Laws of Variation.

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different in their origin—Instinctsgraduated—Aphides and ants—Instinctsvariable—Domestic instincts, their origin—Natural instincts of the cuckoo, ostrich,and parasitic bees—Slave-making ants—Hive-bee, its cell-making instinct—Difficulties on the theory of the NaturalSelection of instincts—Neuter or sterileinsects—Summary

207-244

CHAPTER VIII.

Hybridism.

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—Laws governing the sterility of hybrids—Sterility not a special endowment, butincidental on other differences—Causesof the sterility of first crosses and ofhybrids—Parallelism between the effectsof changed conditions of life and crossing—Fertility of varieties when crossed andof their mongrel offspring not universal—Hybrids and mongrels comparedindependently of their fertility—Summary

245-278

CHAPTER IX.

On the Imperfection of the GeologicalRecord.

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new species—On their different rates ofchange—Species once lost do notreappear—Groups of species follow thesame general rules in their appearance anddisappearance as do single species—OnExtinction—On simultaneous changes inthe forms of life throughout the world—On the affinities of extinct species to eachother and to living species—On the stateof development of ancient forms—On thesuccession of the same types within thesame areas—Summary of preceding andpresent chapters

312-345

CHAPTER XI.

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Present distribution cannot be accountedfor by differences in physical conditions—Importance of barriers—Affinity of theproductions of the same continent—Centres of creation—Means of dispersal,by changes of climate and of the level ofthe land, and by occasional means—Dispersal during the Glacial period co-extensive with the world

346-382

CHAPTER XII.

Geographical Distribution—continued.

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inhabitants of islands to those of thenearest mainland—On colonisation fromthe nearest source with subsequentmodification—Summary of the last andpresent chapters

383-410

CHAPTER XIII.

Mutual Affinities of Organic Beings:Morphology: Embryology: Rudimentary

Organs.

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or adaptive characters—Affinities,general, complex and radiating—Extinction separates and defines groups—Morphology, between members of thesame class, between parts of the sameindividual—Embryology, laws of,explained by variations not supervening atan early age, and being inherited at acorresponding age—Rudimentary organs;their origin explained—Summary

411-458

CHAPTER XIV.

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Society, and it is published in the thirdvolume of the Journal of that Society SirC Lyell and Dr Hooker, who both knewof my work—the latter having read mysketch of 1844—honoured me by thinkingit advisable to publish, with Mr.Wallace's excellent memoir, some briefextracts from my manuscripts.

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a few facts in illustration, but which, Ihope, in most cases will suffice No onecan feel more sensible than I do of thenecessity of hereafter publishing in detailall the facts, with references, on which myconclusions have been grounded; and Ihope in a future work to do this For I amwell aware that scarcely a single point isdiscussed in this volume on which factscannot be adduced, often apparentlyleading to conclusions directly opposite tothose at which I have arrived A fair resultcan be obtained only by fully stating andbalancing the facts and arguments on bothsides of each question; and this cannotpossibly be here done.

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which has seeds that must be transportedby certain birds, and which has flowerswith separate sexes absolutely requiringthe agency of certain insects to bringpollen from one flower to the other, it isequally preposterous to account for thestructure of this parasite, with its relationsto several distinct organic beings, by theeffects of external conditions, or of habit,or of the volition of the plant itself.

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the coadaptations of organic beings toeach other and to their physical conditionsof life, untouched and unexplained.

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studies, although they have been verycommonly neglected by naturalists.

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chapter the Struggle for Existence amongstall organic beings throughout the world,which inevitably follows from the highgeometrical ratio of their increase, will betreated of This is the doctrine of Malthus,applied to the whole animal and vegetablekingdoms As many more individuals ofeach species are born than can possiblysurvive; and as, consequently, there is afrequently recurring struggle for existence,it follows that any being, if it varyhowever slightly in any manner profitableto itself, under the complex and sometimesvarying conditions of life, will have abetter chance of surviving, and thus be

naturally selected From the strong

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powers of animals; thirdly, Hybridism, orthe infertility of species and the fertility ofvarieties when intercrossed; and fourthly,the imperfection of the GeologicalRecord In the next chapter I shallconsider the geological succession oforganic beings throughout time; in theeleventh and twelfth, their geographicaldistribution throughout space; in thethirteenth, their classification or mutualaffinities, both when mature and in anembryonic condition In the last chapter Ishall give a brief recapitulation of thewhole work, and a few concludingremarks.

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view which most naturalists entertain, andwhich I formerly entertained—namely,that each species has been independentlycreated—is erroneous I am fullyconvinced that species are not immutable;but that those belonging to what are calledthe same genera are lineal descendants ofsome other and generally extinct species,in the same manner as the acknowledgedvarieties of any one species are thedescendants of that species Furthermore, Iam convinced that Natural Selection hasbeen the main but not exclusive means ofmodification.

CHAPTER I.

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Causes of Variability—Effectsof Habit—Correlation ofGrowth—Inheritance—Character of Domestic Varieties—Difficulty of distinguishingbetween Varieties and Species—Origin of Domestic Varietiesfrom one or more Species—Domestic Pigeons, theirDifferences and Origin—Principle of Selection ancientlyfollowed, its Effects—Methodical and UnconsciousSelection—Unknown Origin ofour Domestic Productions—Circumstances favourable toMan's power of Selection.

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that this variability may be partlyconnected with excess of food It seemspretty clear that organic beings must beexposed during several generations to thenew conditions of life to cause anyappreciable amount of variation; and thatwhen the organisation has once begun tovary, it generally continues to vary formany generations No case is on record ofa variable being ceasing to be variableunder cultivation Our oldest cultivatedplants, such as wheat, still often yield newvarieties: our oldest domesticated animalsare still capable of rapid improvement ormodification.

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animals and plants withstanddomestication or cultivation, and varyvery slightly—perhaps hardly more thanin a state of nature.

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shown that quite opposite conditionsp r o d uc e similar changes of structure.Nevertheless some slight amount ofchange may, I think, be attributed to thedirect action of the conditions of life—as,in some cases, increased size from amountof food, colour from particular kinds offood or from light, and perhaps thethickness of fur from climate.

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change may be safely attributed to thedomestic duck flying much less, andwalking more, than its wild parent Thegreat and inherited development of theudders in cows and goats in countrieswhere they are habitually milked, incomparison with the state of these organsin other countries, is another instance ofthe effect of use Not a single domesticanimal can be named which has not insome country drooping ears; and the viewsuggested by some authors, that thedrooping is due to the disuse of themuscles of the ear, from the animals notbeing much alarmed by danger, seemsprobable.

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pigs are differently affected from colouredindividuals by certain vegetable poisons.Hairless dogs have imperfect teeth: long-haired and coarse-long-haired animals are aptto have, as is asserted, long or manyhorns; pigeons with feathered feet haveskin between their outer toes; pigeonswith short beaks have small feet, andthose with long beaks large feet Hence, ifman goes on selecting, and thusaugmenting, any peculiarity, he willalmost certainly unconsciously modifyother parts of the structure, owing to themysterious laws of the correlation ofgrowth.

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well worth while carefully to study theseveral treatises published on some of ourold cultivated plants, as on the hyacinth,potato, even the dahlia, &c.; and it isreally surprising to note the endless pointsin structure and constitution in which thevarieties and sub-varieties differ slightlyfrom each other The whole organisationseems to have become plastic, and tendsto depart in some small degree from thatof the parental type.

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albinism, prickly skin, hairy bodies, &c.,appearing in several members of the samefamily If strange and rare deviations ofstructure are truly inherited, less strangeand commoner deviations may be freelyadmitted to be inheritable Perhaps thecorrect way of viewing the whole subject,would be, to look at the inheritance ofevery character whatever as the rule, andnon-inheritance as the anomaly.

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corresponding caterpillar or cocoon stage.But hereditary diseases and some otherfacts make me believe that the rule has awider extension, and that when there is noapparent reason why a peculiarity shouldappear at any particular age, yet that itdoes tend to appear in the offspring at thesame period at which it first appeared inthe parent I believe this rule to be of thehighest importance in explaining the lawsof embryology These remarks are of

course confined to the first appearance of

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male element.

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almost infinite number of generations,would be opposed to all experience I mayadd, that when under nature the conditionsof life do change, variations andreversions of character probably dooccur; but natural selection, as willhereafter be explained, will determinehow far the new characters thus arisingshall be preserved.

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between the several breeds of the dog hasbeen produced under domestication; Ibelieve that some small part of thedifference is due to their being descendedfrom distinct species In the case of someother domesticated species, there ispresumptive, or even strong evidence, thatall the breeds have descended from asingle wild stock.

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degree probable that man sufficientlycivilized to have manufactured potteryexisted in the valley of the Nile thirteen orfourteen thousand years ago; and who willpretend to say how long before theseancient periods, savages, like those ofTierra del Fuego or Australia, whopossess a semi-domestic dog, may nothave existed in Egypt?

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should value more than that of almost anyone, thinks that all the breeds of poultryhave proceeded from the common wildIndian fowl (Gallus bankiva) In regard toducks and rabbits, the breeds of whichdiffer considerably from each other instructure, I do not doubt that they have alldescended from the common wild duckand rabbit.

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rather utter hopelessness, of the taskbecomes apparent Certainly, a breed

intermediate between two very distinct

breeds could not be got without extremecare and long-continued selection; nor canI find a single case on record of apermanent race having been thus formed.

On the Breeds of the Domestic Pigeon.—