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

The Project Gutenberg EBook of On the Origin of Species by Means ofNatural Selection, by Charles Darwin This eBook is for the use of anyone anywhere at no cost and with almost no restric

The Project Gutenberg EBook of On the Origin of Species by Means of

Natural Selection, by Charles Darwin

This eBook is for the use of anyone anywhere at no cost and with

almost no restrictions whatsoever You may copy it, give it away or

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Title: On the Origin of Species by Means

of Natural Selection

or the Preservation of Favoured Races in the Struggle for

Life (2nd edition)

Author: Charles Darwin

Release Date: September 25, 2007 [EBook

#22764]

by insulated interpositions of Divinepower, exerted in each particular case, but

by the establishment of general laws."

Whewell: Bridgewater Treatise.

"The only distinct meaning of the word

'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 of

a weak conceit of sobriety, or an applied moderation, think or maintain, that

ill-a mill-an cill-an seill-arch too fill-ar or be too wellstudied in the book of God's word, or inthe book of God's works; divinity orphilosophy; but rather let men endeavour

an endless progress or proficience inboth."

Bacon: Advancement of Learning.

Down, Bromley, Kent,

October 1st, 1859 (1st Thousand).

ON THE ORIGIN OF

SPECIES

STRUGGLE FOR LIFE.

By CHARLES DARWIN, M.A.,

FELLOW OF THE ROYAL,GEOLOGICAL, LINNEAN, ETC.,

SOCIETIES;

AUTHOR OF 'JOURNAL OFRESEARCHES DURING H M S

BEAGLE'S VOYAGE

ROUND THE WORLD.'

FIFTH THOUSAND.

LONDON:

JOHN MURRAY,

ALBEMARLE STREET.

1860.

The right of Translation is reserved.

LONDON: PRINTED BY W CLOWESAND SONS, STAMFORD STREET,

AND CHARING CROSS

Differences and Origin—Principle ofSelection anciently followed, its Effects—Methodical and Unconscious Selection—Unknown Origin of our DomesticProductions—Circumstances favourable

to Man's power of Selection

7-43

CHAPTER II.

Variation under Nature

Variability—Individual differences—Doubtful species—Wide ranging, muchdiffused, and common species vary most

—Species of the larger genera in anycountry vary more than the species of thesmaller genera—Many of the species ofthe larger genera resemble varieties in

being very closely, but unequally, related

to each other, and in having restrictedranges

44-59

CHAPTER III.

Struggle for Existence

Its bearing on natural selection—The termused in a wide sense—Geometricalpowers of increase—Rapid increase ofnaturalised animals and plants—Nature ofthe checks to increase—Competitionuniversal—Effects of climate—Protectionfrom the number of individuals—Complexrelations of all animals and plantsthroughout nature—Struggle for life mostsevere between individuals and varieties

of the same species; often severe betweenspecies of the same genus—The relation

of organism to organism the mostimportant of all relations

individuals—Slow action—Extinctioncaused by Natural Selection—Divergence

of 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

Acclimatisation—Correlation of growth

—Compensation and economy of growth

—False correlations—Multiple,rudimentary, and lowly organisedstructures variable—Parts developed in

an unusual manner are highly variable:specific characters more variable thangeneric: secondary sexual charactersvariable—Species of the same genus vary

in an analogous manner—Reversions tolong-lost characters—Summary

rarity of transitional varieties—Transitions in habits of life—Diversifiedhabits in the same species—Species withhabits widely different from those of theirallies—Organs of extreme perfection—Means of transition—Cases of difficulty

—Natura non facit saltum—Organs ofsmall importance—Organs not in all casesabsolutely perfect—The law of Unity ofType and of the Conditions of Existenceembraced by the theory of NaturalSelection

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

—Laws governing the sterility of hybrids

—Sterility not a special endowment, butincidental on other differences—Causes

of the sterility of first crosses and ofhybrids—Parallelism between the effects

of changed conditions of life and crossing

—Fertility of varieties when crossed and

of their mongrel offspring not universal—Hybrids and mongrels comparedindependently of their fertility—Summary

intermediate varieties; on their number—

On the vast lapse of time, as inferred fromthe rate of deposition and of denudation—

On the poorness of our palæontologicalcollections—On the intermittence ofgeological formations—On the absence ofintermediate varieties in any oneformation—On the sudden appearance ofgroups of species—On their suddenappearance in the lowest knownfossiliferous strata

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 state

of development of ancient forms—On thesuccession of the same types within thesame areas—Summary of preceding andpresent chapters

312-345

CHAPTER XI.

Geographical Distribution

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.

Distribution of fresh-water productions—

On the inhabitants of oceanic islands—Absence of Batrachians and of terrestrialMammals—On the relation of the

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

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 at

an early age, and being inherited at acorresponding age—Rudimentary organs;their origin explained—Summary

411-458

CHAPTER XIV.

Recapitulation and Conclusion.Recapitulation of the difficulties on thetheory of Natural Selection—Recapitulation of the general and special

circumstances in its favour—Causes of thegeneral belief in the immutability ofspecies—How far the theory of naturalselection may be extended—Effects of itsadoption on the study of Natural history—Concluding remarks

459-490

ON THE ORIGIN

OF SPECIES INTRODUCTION.

When on board H.M.S 'Beagle,' as

naturalist, I was much struck with certainfacts in the distribution of the inhabitants

of South America, and in the geologicalrelations of the present to the pastinhabitants of that continent These factsseemed to me to throw some light on theorigin of species—that mystery ofmysteries, as it has been called by one ofour greatest philosophers On my returnhome, it occurred to me, in 1837, thatsomething might perhaps be made out onthis question by patiently accumulatingand reflecting on all sorts of facts whichcould possibly have any bearing on it.After five years' work I allowed myself tospeculate on the subject, and drew upsome short notes; these I enlarged in 1844into a sketch of the conclusions, whichthen seemed to me probable: from that

period to the present day I have steadilypursued the same object I hope that I may

be excused for entering on these personaldetails, as I give them to show that I havenot been hasty in coming to a decision

My work is now nearly finished; but as itwill take me two or three more years tocomplete it, and as my health is far fromstrong, I have been urged to publish thisAbstract I have more especially beeninduced to do this, as Mr Wallace, who isnow studying the natural history of theMalay archipelago, has arrived at almostexactly the same general conclusions that Ihave on the origin of species Last year hesent me a memoir on this subject, with arequest that I would forward it to SirCharles Lyell, who sent it to the Linnean

Society, and it is published in the thirdvolume of the Journal of that Society Sir

C Lyell and Dr Hooker, who both knew

of my work—the latter having read mysketch of 1844—honoured me by thinking

it advisable to publish, with Mr.Wallace's excellent memoir, some briefextracts from my manuscripts

This Abstract, which I now publish, mustnecessarily be imperfect I cannot heregive references and authorities for myseveral statements; and I must trust to thereader reposing some confidence in myaccuracy No doubt errors will have crept

in, though I hope I have always beencautious in trusting to good authoritiesalone I can here give only the generalconclusions at which I have arrived, with

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.

I much regret that want of space prevents

my having the satisfaction of

acknowledging the generous assistancewhich I have received from very manynaturalists, some of them personallyunknown to me I cannot, however, let thisopportunity pass without expressing mydeep obligations to Dr Hooker, who forthe last fifteen years has aided me in everypossible way by his large stores ofknowledge and his excellent judgment.

In considering the Origin of Species, it isquite conceivable that a naturalist,reflecting on the mutual affinities oforganic beings, on their embryologicalrelations, their geographical distribution,geological succession, and other suchfacts, might come to the conclusion thateach species had not been independentlycreated, but had descended, like varieties,

from other species Nevertheless, such aconclusion, even if well founded, would

be unsatisfactory, until it could be shownhow the innumerable species inhabitingthis world have been modified, so as toacquire that perfection of structure andcoadaptation which most justly excites ouradmiration Naturalists continually refer toexternal conditions, such as climate, food,

&c., as the only possible cause ofvariation In one very limited sense, as weshall hereafter see, this may be true; but it

is preposterous to attribute to mereexternal conditions, the structure, forinstance, of the woodpecker, with its feet,tail, beak, and tongue, so admirablyadapted to catch insects under the bark oftrees In the case of the misseltoe, whichdraws its nourishment from certain trees,

which has seeds that must be transported

by 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 relations

to several distinct organic beings, by theeffects of external 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 certainunknown number of generations, somebird had given birth to a woodpecker, andsome plant to the missletoe, and that thesehad been produced perfect as we now seethem; but this assumption seems to me to

be no explanation, for it leaves the case of

the coadaptations of organic beings toeach other and to their physical conditions

of life, untouched and unexplained

It is, therefore, of the highest importance

to gain a clear insight into the means ofmodification and coadaptation At thecommencement of my observations itseemed to me probable that a careful study

of domesticated animals and of cultivatedplants would offer the best chance ofmaking out this obscure problem Norhave I been disappointed; in this and in allother perplexing cases I have invariablyfound that our knowledge, imperfectthough it be, of variation underdomestication, afforded the best and safestclue I may venture to express myconviction of the high value of such

studies, although they have been verycommonly neglected by naturalists.

From these considerations, I shall devotethe first chapter of this Abstract toVariation under Domestication We shallthus see that a large amount of hereditarymodification is at least possible; and,what is equally or more important, weshall see how great is the power of man inaccumulating by his Selection successiveslight variations I will then pass on to thevariability of species in a state of nature;but I shall, unfortunately, be compelled totreat this subject far too briefly, as it can

be treated properly only by giving longcatalogues of facts We shall, however, beenabled to discuss what circumstances aremost favourable to variation In the next

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 profitable

to itself, under the complex and sometimesvarying conditions of life, will have abetter chance of surviving, and thus be

naturally selected From the strong

principle of inheritance, any selectedvariety will tend to propagate its new andmodified form

This fundamental subject of NaturalSelection will be treated at some length inthe fourth chapter; and we shall then seehow Natural Selection almost inevitablycauses much Extinction of the lessimproved forms of life, and leads to what

I have called Divergence of Character Inthe next chapter I shall discuss thecomplex and little known laws ofvariation and of correlation of growth Inthe four succeeding chapters, the mostapparent and gravest difficulties on thetheory will be given: namely, first, thedifficulties of transitions, or inunderstanding how a simple being or asimple organ can be changed andperfected into a highly developed being orelaborately constructed organ; secondly,the subject of Instinct, or the mental

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.

No one ought to feel surprise at muchremaining as yet unexplained in regard tothe origin of species and varieties, if he

makes due allowance for our profoundignorance in regard to the mutual relations

of all the beings which live around us.Who can explain why one species rangeswidely and is very numerous, and whyanother allied species has a narrow rangeand is rare? Yet these relations are of thehighest importance, for they determine thepresent welfare, and, as I believe, thefuture success and modification of everyinhabitant of this world Still less do weknow of the mutual relations of theinnumerable inhabitants of the worldduring the many past geological epochs inits history Although much remainsobscure, and will long remain obscure, Ican entertain no doubt, after the mostdeliberate study and dispassionatejudgment of which I am capable, that the

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, I

am convinced that Natural Selection hasbeen the main but not exclusive means ofmodification

CHAPTER I.

Variation under Domestication

Causes of Variability—Effects

of 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

When we look to the individuals of the

same variety or sub-variety of our oldercultivated plants and animals, one of thefirst points which strikes us, is, that theygenerally differ more from each other than

do the individuals of any one species orvariety in a state of nature When wereflect on the vast diversity of the plantsand animals which have been cultivated,and which have varied during all agesunder the most different climates andtreatment, I think we are driven toconclude that this great variability issimply due to our domestic productionshaving been raised under conditions oflife not so uniform as, and somewhatdifferent from, those to which the parent-species have been exposed under nature.There is also, I think, some probability inthe view propounded by Andrew Knight,