CHAPTER I.

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1228 1859, First Edition

22764 1860, Second Edition

2009 1872, Sixth Edition, considered the definitive edition.

On the Origin of Species

BY MEANS OF NATURAL SELECTION,

OR THE PRESERVATION OF FAVOURED RACES IN THE STRUGGLE FOR LIFE.

By Charles Darwin, M.A., F.R.S.,

Author of “The Descent of Man,” etc., etc.

Sixth London Edition, with all Additions and Corrections.

“But with regard to the material world, we can at least go so far as

this—we can perceive that events are brought about not by insulated

interpositions of Divine power, 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 and presupposes an

intelligent agent to render it so, _i.e._, to effect it continually or

at stated times, as what is supernatural or miraculous 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 ill-applied moderation, think or maintain, that a man can search

too far or be too well studied in the book of God’s word, or in the

book of God’s works; divinity or philosophy; but rather let men

endeavour an endless progress or proficience in both.”

BACON: _Advancement of Learning_.

AN HISTORICAL SKETCH OF THE PROGRESS OF OPINION ON THE ORIGIN OF

SPECIES, PREVIOUSLY TO THE PUBLICATION OF THE FIRST EDITION OF THIS

WORK.

I will here give a brief sketch of the progress of opinion on the

Origin of Species. Until recently the great majority of naturalists

believed that species were immutable productions, and had been

separately created. This view has been ably maintained by many authors.

Some few naturalists, on the other hand, have believed that species

undergo modification, and that the existing forms of life are the

descendants by true generation of pre existing forms. Passing over

allusions to the subject in the classical writers,[1] the first author

who in modern times has treated it in a scientific spirit was Buffon.

But as his opinions fluctuated greatly at different periods, and as he

does not enter on the causes or means of the transformation of species,

I need not here enter on details.

[1] Aristotle, in his “Physicæ Auscultationes” (lib.2, cap.8, s.2),

after remarking that rain does not fall in order to make the corn

grow, any more than it falls to spoil the farmer’s corn when threshed

out of doors, applies the same argument to organisation; and adds (as

translated by Mr. Clair Grece, who first pointed out the passage to

me), “So what hinders the different parts (of the body) from having

this merely accidental relation in nature? as the teeth, for example,

grow by 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 sake of this, but it was the result of accident.

And in like manner as to other parts in which there appears to exist

an adaptation to an end. Wheresoever, therefore, all things together

(that is all the parts of one whole) happened like as if they were

made for the sake of something, these were preserved, having been

appropriately constituted by an internal spontaneity; and whatsoever

things were not thus constituted, perished and still perish.” We here

see the principle of natural selection shadowed forth, but how little

Aristotle fully comprehended the principle, is shown by his remarks on

the formation of the teeth.

Lamarck was the first man whose conclusions on the subject excited much

attention. This justly celebrated naturalist first published his views

in 1801; he much enlarged them in 1809 in his “Philosophie Zoologique”,

and subsequently, 1815, in the Introduction to his “Hist. Nat. des

Animaux sans Vertébres”. In these works he up holds the doctrine that

all species, including man, are descended from other species. He first

did the eminent service of arousing attention to the probability of all

change in the organic, as well as in the inorganic world, being the

result of law, and not of miraculous interposition. Lamarck seems to

have been chiefly led to his conclusion on the gradual change of

species, by the difficulty of distinguishing species and varieties, by

the almost perfect gradation of forms in certain groups, and by the

analogy of domestic productions. With respect to the means of

modification, he attributed something to the direct action of the

physical conditions of life, something to the crossing of already

existing forms, and much to use and disuse, that is, to the effects of

habit. To this latter agency he seems to attribute all the beautiful

adaptations in nature; such as the long neck of the giraffe for

browsing on the branches of trees. But he likewise believed in a law of

progressive development, and as all the forms of life thus tend to

progress, in order to account for the existence at the present day of

simple productions, he maintains that such forms are now spontaneously

generated.[2]

[2] I have taken the date of the first publication of Lamarck from

Isidore Geoffroy Saint-Hilaire’s (“Hist. Nat. Générale”, tom. ii. page

405, 1859) excellent history of opinion on this subject. In this work

a full account is given of Buffon’s conclusions on the same subject.

It is curious how largely my grandfather, Dr. Erasmus Darwin,

anticipated the views and erroneous grounds of opinion of Lamarck in

his “Zoonomia” (vol. i. pages 500-510), published in 1794. According

to Isid. Geoffroy there is no doubt that Goethe was an extreme

partisan of similar views, as shown in the introduction to a work

written in 1794 and 1795, but not published till long afterward; he

has pointedly remarked (“Goethe als Naturforscher”, von Dr. Karl

Meding, s. 34) that the future question for naturalists will 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 at about the same time, that Goethe in Germany, Dr. Darwin in

England, and Geoffroy Saint-Hilaire (as we shall immediately see) in

France, came to the same 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 various

degenerations of the same type. It was not until 1828 that he published

his conviction that the same forms have not been perpetuated since the

origin of all things. Geoffroy seems to have relied chiefly on the

conditions of life, or the “_monde ambiant_” as the cause of change. He

was cautious in drawing conclusions, and did not believe that existing

species are now undergoing modification; and, as his son adds, “C’est

donc un problème à réserver entièrement à l’avenir, supposé même que

l’avenir doive avoir prise sur lui.”

In 1813 Dr. W.C. Wells read before the Royal Society “An Account of a

White Female, part of whose skin resembles that of a Negro”; but his

paper was not published until his famous “Two Essays upon Dew and

Single Vision” appeared in 1818. In this paper he distinctly recognises

the principle of natural selection, and this is the first recognition

which has been indicated; but he applies it only to the races of man,

and to certain characters alone. After remarking that negroes and

mulattoes enjoy an immunity from certain tropical diseases, he

observes, firstly, that all animals tend to vary in some degree, and,

secondly, that agriculturists improve their domesticated animals by

selection; and then, he adds, but what is done in this latter case “by

art, seems to be done with equal efficacy, though more slowly, by

nature, in the formation of varieties of mankind, fitted for the

country which they inhabit. Of the accidental varieties of man, which

would occur among the first few and scattered inhabitants of the middle

regions of Africa, some one would be better fitted than others to bear

the diseases of the country. This race would consequently multiply,

while the others would decrease; not only from their in ability to

sustain the attacks of disease, but from their incapacity of contending

with their more vigorous neighbours. The colour of this vigorous race I

take for granted, from what has been already said, would be dark. But

the same disposition to form varieties still existing, a darker and a

darker race would in the course of time occur: and as the darkest would

be the best fitted for the climate, this would at length become the

most prevalent, if not the only race, in the particular country in

which it had originated.” He then extends these same views to the white

inhabitants of colder climates. I am indebted to Mr. Rowley, of the

United States, for having called my attention, through Mr. Brace, to

the above passage of Dr. Wells’ work.

The Hon. and Rev. W. Herbert, afterward Dean of Manchester, in the

fourth volume of the “Horticultural Transactions”, 1822, and in his

work on the “Amaryllidaceæ” (1837, pages 19, 339), declares that

“horticultural experiments have established, beyond the possibility of

refutation, that botanical species are only a higher and more permanent

class of varieties.” He extends the same view to animals. The dean

believes that single species of each genus were created in an

originally highly plastic condition, and that these have produced,

chiefly by inter-crossing, but likewise by variation, all our existing

species.

In 1826 Professor Grant, in the concluding paragraph in his well-known

paper (“Edinburgh Philosophical Journal”, vol. XIV, page 283) on the

Spongilla, clearly declares his belief that species are descended from

other species, and that they become improved in the course of

modification. This same view was given in his Fifty-fifth Lecture,

published in the “Lancet” in 1834.

In 1831 Mr. Patrick Matthew published his work on “Naval Timber and

Arboriculture”, in which he gives precisely the same view on the origin

of species as that (presently to be alluded to) propounded by Mr.

Wallace and myself in the “Linnean Journal”, and as that enlarged in

the present volume. Unfortunately the view was given by Mr. Matthew

very briefly in scattered passages in an appendix to a work on a

different subject, so that it remained unnoticed until Mr. Matthew

himself drew attention to it in the “Gardeners’ Chronicle”, on April 7,

1860. The differences of Mr. Matthew’s views from mine are not of much

importance: he seems to consider that the world was nearly depopulated

at successive periods, and then restocked; and he gives as an

alternative, that new forms may be generated “without the presence of

any mold or germ of former aggregates.” I am not sure that I understand

some passages; but it seems that he attributes much influence to the

direct action of the conditions of life. He clearly saw, however, the

full force of the principle of natural selection.

The celebrated geologist and naturalist, Von Buch, in his excellent

“Description Physique des Isles Canaries” (1836, page 147), clearly

expresses his belief that varieties slowly become changed into

permanent species, which are no longer capable of intercrossing.

Rafinesque, in his “New Flora of North America”, published in 1836,

wrote (page 6) as follows: “All species might have been varieties once,

and many varieties are gradually becoming species by assuming constant

and peculiar characters;” but further on (page 18) he adds, “except the

original types or ancestors of the genus.”

In 1843-44 Professor Haldeman (“Boston Journal of Nat. Hist. U.

States”, vol. iv, page 468) has ably given the arguments for and

against the hypothesis of the development and modification of species:

he seems to lean toward the side of change.

The “Vestiges of Creation” appeared in 1844. In the tenth and much

improved edition (1853) the anonymous author says (page 155): “The

proposition determined on after much consideration is, that the several

series of animated beings, from the simplest and oldest up to the

highest and most recent, are, under the providence of God, the results,

_first_, of an impulse which has been imparted to the forms of life,

advancing them, in definite times, by generation, through grades of

organisation terminating in the highest dicotyledons and vertebrata,

these grades being few in number, and generally marked by intervals of

organic character, which we find to be a practical difficulty in

ascertaining affinities; _second_, of another impulse connected with

the vital forces, tending, in the course of generations, to modify

organic structures in accordance with external circumstances, as food,

the nature of the habitat, and the meteoric agencies, these being the

‘adaptations’ of the natural theologian.” The author apparently

believes that organisation progresses by sudden leaps, but that the

effects produced by the conditions of life are gradual. He argues with

much force on general grounds that species are not immutable

productions. But I cannot see how the two supposed “impulses” account

in a scientific sense for the numerous and beautiful coadaptations

which we see throughout nature; I cannot see that we thus gain any

insight how, for instance, a woodpecker has become adapted to its

peculiar habits of life. The work, from its powerful and brilliant

style, though displaying in the early editions little accurate

knowledge and a great want of scientific caution, immediately had a

very wide circulation. In my opinion it has done excellent service in

this country in calling attention to the subject, in removing

prejudice, and in thus preparing the ground for the reception of

analogous views.

In 1846 the veteran geologist M.J. d’Omalius d’Halloy published in an

excellent though short paper (“Bulletins de l’Acad. Roy. Bruxelles”,

tom. xiii, page 581) his opinion that it is more probable that new

species have been produced by descent with modification than that they

have been separately created: the author first promulgated this opinion

in 1831.

Professor Owen, in 1849 (“Nature of Limbs”, page 86), wrote as follows:

“The archetypal idea was manifested in the flesh under diverse such

modifications, upon this planet, long prior to the existence of those

animal species that actually exemplify it. To what natural laws or

secondary causes the orderly succession and progression of such organic

phenomena may have been committed, we, as yet, are ignorant.” In his

address to the British Association, in 1858, he speaks (page li) of

“the axiom of the continuous operation of creative power, or of the

ordained becoming of living things.” Further on (page xc), after

referring to geographical distribution, he adds, “These phenomena shake

our confidence in the conclusion that the Apteryx of New Zealand and

the Red Grouse of England were distinct creations in and for those

islands respectively. Always, also, it may be well to bear in mind that

by the word ‘creation’ the zoologist means ‘a process he knows not

what.’” He amplifies this idea by adding that when such cases as that

of the Red Grouse are “enumerated by the zoologist as evidence of

distinct creation of the bird in and for such islands, he chiefly

expresses that he knows not how the Red Grouse came to be there, and

there exclusively; signifying also, by this mode of expressing such

ignorance, his belief that both the bird and the islands owed their

origin to a great first Creative Cause.” If we interpret these

sentences given in the same address, one by the other, it appears that

this eminent philosopher felt in 1858 his confidence shaken that the

Apteryx and the Red Grouse first appeared in their respective homes “he

knew not how,” or by some process “he knew not what.”

This Address was delivered after the papers by Mr. Wallace and myself

on the Origin of Species, presently to be referred to, had been read

before the Linnean Society. When the first edition of this work was

published, I was so completely deceived, as were many others, by such

expressions as “the continuous operation of creative power,” that I

included Professor Owen with other palæontologists as being firmly

convinced of the immutability of species; but it appears (“Anat. of

Vertebrates”, vol. iii, page 796) that this was on my part a

preposterous error. In the last edition of this work I inferred, and

the inference still seems to me perfectly just, from a passage

beginning with the words “no doubt the type-form,” &c.(Ibid., vol. i,

page xxxv), that Professor Owen admitted that natural selection may

have done something in the formation of a new species; but this it

appears (Ibid., vol. iii. page 798) is inaccurate and without evidence.

I also gave some extracts from a correspondence between Professor Owen

and the editor of the “London Review”, from which it appeared manifest

to the editor as well as to myself, that Professor Owen claimed to have

promulgated the theory of natural selection before I had done so; and I

expressed my surprise and satisfaction at this announcement; but as far

as it is possible to understand certain recently published passages

(Ibid., vol. iii. page 798) I have either partially or wholly again

fallen into error. It is consolatory to me that others find Professor

Owen’s controversial writings as difficult to understand and to

reconcile with each other, as I do. As far as the mere enunciation of

the principle of natural selection is concerned, it is quite immaterial

whether or not Professor Owen preceded me, for both of us, as shown in

this historical sketch, were long ago preceded by Dr. Wells and Mr.

Matthews.

M. Isidore Geoffroy Saint-Hilaire, in his lectures delivered in 1850

(of which 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 des

mêmes circonstances: ils se modifient, si les circonstances ambiantes

viennent à changer. En résumé, _l’observation_ des animaux sauvages

démontre deja la variabilité _limitée_ des espèces. Les _expériences_

sur les animaux sauvages devenus domestiques, et sur les animaux

domestiques redevenus sauvages, la démontrent plus clairment encore.

Ces mêmes expériences prouvent, de plus, que les différences produites

peuvent être de _valeur générique_.” In his “Hist. Nat. Générale” (tom.

ii, page 430, 1859) he amplifies analogous conclusions.

From a circular lately issued it appears that Dr. Freke, in 1851

(“Dublin Medical Press”, page 322), propounded the doctrine that all

organic beings have descended from one primordial form. His grounds of

belief and treatment of the subject are wholly different from mine; but

as Dr. Freke has now (1861) published his Essay on the “Origin of

Species by means of Organic Affinity”, the difficult attempt to give

any idea of his views would 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 contrasted

the theories of the Creation and the Development of organic beings with

remarkable skill and force. He argues from the analogy of domestic

productions, from the changes which the embryos of many species

undergo, from the difficulty of distinguishing species and varieties,

and from the principle of general gradation, that species have been

modified; and he attributes the modification to the change of

circumstances. The author (1855) has also treated Psychology on the

principle of the necessary acquirement of each mental power and

capacity by gradation.

In 1852 M. Naudin, a distinguished botanist, expressly stated, in an

admirable paper on the Origin of Species (“Revue Horticole”, page 102;

since partly republished in the “Nouvelles Archives du Muséum”, tom. i,

p. 171), his belief that species are formed in an analogous manner as

varieties are under cultivation; and the latter process he attributes

to man’s power of selection. But he does not show how selection acts

under nature. He believes, like Dean Herbert, that species, when

nascent, were more plastic than at present. He lays weight on what he

calls the principle of finality, “puissance mystérieuse, indéterminée;

fatalité pour les uns; pour les autres volonté providentielle, dont

l’action incessante sur les êtres vivantes détermine, à toutes les

époques de l’existence du monde, la 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’est cette puissance qui harmonise chaque membre à

l’ensemble, en l’appropriant à la fonction qu’il doit remplir dans

l’organisme général de la nature, fonction qui est pour lui sa raison

d’être.”[3]

[3] From references in Bronn’s “Untersuchungen über die

Entwickelungs-Gesetze”, it appears that the celebrated botanist and

palæontologist Unger published, in 1852, his belief that species

undergo development and modification. Dalton, likewise, in Pander and

Dalton’s work on Fossil Sloths, expressed, in 1821, a similar belief.

Similar views have, as is well known, been maintained by Oken in his

mystical “Natur-Philosophie”. From other 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 continually being

produced.

I may add, that of the thirty-four authors named in this Historical

Sketch, who believe in the modification of species, or at least

disbelieve in separate acts of creation, twenty-seven have written

on special branches of natural history or geology.

In 1853 a celebrated geologist, Count Keyserling (“Bulletin de la Soc.

Geolog.”, 2nd Ser., tom. x, page 357), suggested that as new diseases,

supposed to have been caused by some miasma have arisen and spread over

the world, so at certain periods the germs of existing species may have

been chemically affected by circumambient molecules of a particular

nature, and thus have given rise to new forms.

In this same year, 1853, Dr. Schaaffhausen published an excellent

pamphlet (“Verhand. des Naturhist. Vereins der Preuss. Rheinlands”,

&c.), in which he maintains the development of organic forms on the

earth. He infers that many species have kept true for long periods,

whereas a few have become modified. The distinction of species he

explains by the destruction of intermediate graduated forms. “Thus

living plants and animals are not separated from the extinct by new

creations, but are to be regarded as their descendants through

continued reproduction.”

A well-known French botanist, M. Lecoq, writes in 1854 (“Etudes sur

Géograph.” Bot. tom. i, page 250), “On voit que nos recherches sur la

fixité ou la variation de l’espéce, nous conduisent directement aux

idées émises par deux hommes justement célèbres, Geoffroy Saint-Hilaire

et Goethe.” Some other passages scattered through M. Lecoq’s large work

make it a little doubtful how far he extends his views on the

modification of species.

The “Philosophy of Creation” has been treated in a masterly manner by

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 that the

introduction of new species is “a regular, not a casual phenomenon,”

or, as Sir John Herschel expresses it, “a natural in contradistinction

to a miraculous process.”

The third volume of the “Journal of the Linnean Society” contains

papers, read July 1, 1858, by Mr. Wallace and myself, in which, as

stated in the introductory remarks to this volume, the theory of

Natural Selection is promulgated by Mr. Wallace with admirable force

and clearness.

Von Baer, toward whom all zoologists feel so profound a respect,

expressed about the year 1859 (see Prof. Rudolph Wagner,

“Zoologisch-Anthropologische Untersuchungen”, 1861, s. 51) his

conviction, chiefly grounded on the laws of geographical distribution,

that forms now perfectly distinct have descended from a single

parent-form.

In June, 1859, Professor Huxley gave a lecture before the Royal

Institution on the ‘Persistent Types of Animal Life’. Referring to such

cases, he remarks, “It is difficult to comprehend the meaning of such

facts as these, if we suppose that each species of animal and plant, or

each great type of organisation, was formed and placed upon the surface

of the globe at long intervals by a distinct act of creative power; and

it is well to recollect that such an assumption is as unsupported by

tradition or revelation as it is opposed to the general analogy of

nature. If, on the other hand, we view ‘Persistent Types’ in relation

to that hypothesis which supposes the species living at any time to be

the result of the gradual modification of pre-existing species, a

hypothesis which, though unproven, and sadly damaged by some of its

supporters, is yet the only one to which physiology lends any

countenance; their existence would seem to show that the amount of

modification which living beings have undergone during geological time

is but very small in relation to the whole series of changes which they

have suffered.”

In December, 1859, Dr. Hooker published his “Introduction to the

Australian Flora”. In the first part of this great work he admits the

truth of the descent and modification of species, and supports this

doctrine by many original observations.

The first edition of this work was published on November 24, 1859, and

the second edition on January 7, 1860.

Contents

AN HISTORICAL SKETCH OF THE PROGRESS OF OPINION ON THE ORIGIN OF SPECIES

INTRODUCTION.

CHAPTER I. VARIATION UNDER DOMESTICATION

CHAPTER II. VARIATION UNDER NATURE

CHAPTER III. STRUGGLE FOR EXISTENCE

CHAPTER IV. NATURAL SELECTION; OR THE SURVIVAL OF THE FITTEST

CHAPTER V. LAWS OF VARIATION

CHAPTER VI. DIFFICULTIES OF THE THEORY

CHAPTER VII. MISCELLANEOUS OBJECTIONS TO THE THEORY OF NATURAL SELECTION

CHAPTER VIII. INSTINCT

CHAPTER IX. HYBRIDISM

CHAPTER X. ON THE IMPERFECTION OF THE GEOLOGICAL RECORD

CHAPTER XI. ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS

CHAPTER XII. GEOGRAPHICAL DISTRIBUTION

CHAPTER XIII. GEOGRAPHICAL DISTRIBUTION—continued

CHAPTER XIV. MUTUAL AFFINITIES OF ORGANIC BEINGS

CHAPTER XV. RECAPITULATION AND CONCLUSION

GLOSSARY OF THE PRINCIPAL SCIENTIFIC TERMS USED IN THE PRESENT VOLUME.

INDEX.

DETAILED CONTENTS.

INTRODUCTION

CHAPTER I.

VARIATION UNDER DOMESTICATION.

Causes of Variability—Effects of Habit and the use or disuse of

Parts—Correlated Variation—Inheritance—Character of Domestic

Varieties—Difficulty of distinguishing between Varieties and

Species—Origin of Domestic Varieties from one or more Species—Domestic

Pigeons, their Differences and Origin—Principles of Selection,

anciently followed, their Effects—Methodical and Unconscious

Selection—Unknown Origin of our Domestic Productions—Circumstances

favourable to Man’s power of Selection.

CHAPTER II.

VARIATION UNDER NATURE.

Variability—Individual Differences—Doubtful species—Wide ranging, much

diffused, and common species, vary most—Species of the larger genera in

each country vary more frequently than the species of the smaller

genera—Many of the species of the larger genera resemble varieties in

being very closely, but unequally, related to each other, and in having

restricted ranges.

CHAPTER III.

STRUGGLE FOR EXISTENCE.

Its bearing on natural selection—The term used in a wide

sense—Geometrical ratio of increase—Rapid increase of naturalised

animals and plants—Nature of the checks to increase—Competition

universal—Effects of climate—Protection from the number of

individuals—Complex relations of all animals and plants throughout

nature—Struggle for life most severe between individuals and varieties

of the same species; often severe between species of the same genus—The

relation of organism to organism the most important of all relations.

CHAPTER IV.

NATURAL SELECTION; OR THE SURVIVAL OF THE FITTEST.

Natural Selection—its power compared with man’s selection—its power on

characters of trifling importance—its power at all ages and on both

sexes—Sexual Selection—On the generality of intercrosses between

individuals of the same species—Circumstances favourable and

unfavourable to the results of Natural Selection, namely,

intercrossing, isolation, number of individuals—Slow action—Extinction

caused by Natural Selection—Divergence of Character, related to the

diversity of inhabitants of any small area and to naturalisation—Action

of Natural Selection, through Divergence of Character and Extinction,

on the descendants from a common parent—Explains the Grouping of all

organic beings—Advance in organisation—Low forms preserved—Convergence

of character—Indefinite multiplication of species—Summary.

CHAPTER V.

LAWS OF VARIATION.

Effects of changed conditions—Use and disuse, combined with natural

selection; organs of flight and of vision—Acclimatisation—Correlated

variation—Compensation and economy of growth—False

correlations—Multiple, rudimentary, and lowly organised structures

variable—Parts developed in an unusual manner are highly variable;

specific characters more variable than generic; secondary sexual

characters variable—Species of the same genus vary in an analogous

manner—Reversions to long-lost characters—Summary.

CHAPTER VI.

DIFFICULTIES OF THE THEORY.

Difficulties of the theory of descent with modification—Absence or

rarity of transitional varieties—Transitions in habits of

life—Diversified habits in the same species—Species with habits widely

different from those of their allies—Organs of extreme perfection—Modes

of transition—Cases of difficulty—Natura non facit saltum—Organs of

small importance—Organs not in all cases absolutely perfect—The law of

Unity of Type and of the Conditions of Existence embraced by the theory

of Natural Selection.

CHAPTER VII.

MISCELLANEOUS OBJECTIONS TO THE THEORY OF NATURAL SELECTION.

Longevity—Modifications not necessarily simultaneous—Modifications

apparently of no direct service—Progressive development—Characters of

small functional importance, the most constant—Supposed incompetence of

natural selection to account for the incipient stages of useful

structures—Causes which interfere with the acquisition through natural

selection of useful structures—Gradations of structure with changed

functions—Widely different organs in members of the same class,

developed from one and the same source—Reasons for disbelieving in

great and abrupt modifications.

CHAPTER VIII.

INSTINCT.

Instincts comparable with habits, but different in their

origin—Instincts graduated—Aphides and ants—Instincts variable—Domestic

instincts, their origin—Natural instincts of the cuckoo, molothrus,

ostrich, and parasitic bees—Slave-making ants—Hive-bee, its cell-making

instinct—Changes of instinct and structure not necessarily

simultaneous—Difficulties on the theory of the Natural Selection of

instincts—Neuter or sterile insects—Summary.

CHAPTER IX.

HYBRIDISM.

Distinction between the sterility of first crosses and of

hybrids—Sterility various in degree, not universal, affected by close

interbreeding, removed by domestication—Laws governing the sterility of

hybrids—Sterility not a special endowment, but incidental on other

differences, not accumulated by natural selection—Causes of the

sterility of first crosses and of hybrids—Parallelism between the

effects of changed conditions of life and of crossing—Dimorphism and

Trimorphism—Fertility of varieties when crossed and of their mongrel

offspring not universal—Hybrids and mongrels compared independently of

their fertility—Summary.

CHAPTER X.

ON THE IMPERFECTION OF THE GEOLOGICAL RECORD.

On the absence of intermediate varieties at the present day—On the

nature of extinct intermediate varieties; on their number—On the lapse

of time, as inferred from the rate of denudation and of deposition—On

the lapse of time as estimated in years—On the poorness of our

palæontological collections—On the intermittence of geological

formations—On the denudation of granitic areas—On the absence of

intermediate varieties in any one formation—On the sudden appearance of

groups of species—On their sudden appearance in the lowest known

fossiliferous strata—Antiquity of the habitable earth.

CHAPTER XI.

ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS.

On the slow and successive appearance of new species—On their different

rates of change—Species once lost do not reappear—Groups of species

follow the same general rules in their appearance and disappearance as

do single species—On extinction—On simultaneous changes in the forms of

life throughout the world—On the affinities of extinct species to each

other and to living species—On the state of development of ancient

forms—On the succession of the same types within the same areas—Summary

of preceding and present chapter.

CHAPTER XII.

GEOGRAPHICAL DISTRIBUTION.

Present distribution cannot be accounted for by differences in physical

conditions—Importance of barriers—Affinity of the productions of the

same continent—Centres of creation—Means of dispersal by changes of

climate and of the level of the land, and by occasional means—Dispersal

during the Glacial period—Alternate Glacial periods in the north and

south.

CHAPTER XIII.

GEOGRAPHICAL DISTRIBUTION—_continued_.

Distribution of fresh-water productions—On the inhabitants of oceanic

islands—Absence of Batrachians and of terrestrial Mammals—On the

relation of the inhabitants of islands to those of the nearest

mainland—On colonisation from the nearest source with subsequent

modification—Summary of the last and present chapter.

CHAPTER XIV.

MUTUAL AFFINITIES OF ORGANIC BEINGS:

MORPHOLOGY: EMBRYOLOGY: RUDIMENTARY ORGANS.

Classification, groups subordinate to groups—Natural system—Rules and

difficulties in classification, explained on the theory of descent with

modification—Classification of varieties—Descent always used in

classification—Analogical or adaptive characters—Affinities, general,

complex and radiating—Extinction separates and defines

groups—Morphology, between members of the same class, between parts of

the same individual—Embryology, laws of, explained by variations not

supervening at an early age, and being inherited at a corresponding

age—Rudimentary Organs; their origin explained—Summary.

CHAPTER XV.

RECAPITULATION AND CONCLUSION.

Recapitulation of the objections to the theory of Natural

Selection—Recapitulation of the general and special circumstances in

its favour—Causes of the general belief in the immutability of

species—How far the theory of Natural Selection may be extended—Effects

of its adoption on the study of Natural history—Concluding remarks.

GLOSSARY OF SCIENTIFIC TERMS.

INDEX.

ORIGIN OF SPECIES.

INTRODUCTION.

When on board H.M.S. Beagle, as naturalist, I was much struck with

certain facts in the distribution of the organic beings inhabiting

South America, and in the geological relations of the present to the

past inhabitants of that continent. These facts, as will be seen in the

latter chapters of this volume, seemed to throw some light on the

origin of species—that mystery of mysteries, as it has been called by

one of our greatest philosophers. On my return home, it occurred to me,

in 1837, that something might perhaps be made out on this question by

patiently accumulating and reflecting on all sorts of facts which could

possibly have any bearing on it. After five years’ work I allowed

myself to speculate on the subject, and drew up some short notes; these

I enlarged in 1844 into a sketch of the conclusions, which then seemed

to me probable: from that period to the present day I have steadily

pursued the same object. I hope that I may be excused for entering on

these personal details, as I give them to show that I have not been

hasty in coming to a decision.

My work is now (1859) nearly finished; but as it will take me many more

years to complete it, and as my health is far from strong, I have been

urged to publish this abstract. I have more especially been induced to

do this, as Mr. Wallace, who is now studying the natural history of the

Malay Archipelago, has arrived at almost exactly the same general

conclusions that I have on the origin of species. In 1858 he sent me a

memoir on this subject, with a request that I would forward it to Sir

Charles Lyell, who sent it to the Linnean Society, and it is published

in the third volume of the Journal of that Society. Sir C. Lyell and

Dr. Hooker, who both knew of my work—the latter having read my sketch

of 1844—honoured me by thinking it advisable to publish, with Mr.

Wallace’s excellent memoir, some brief extracts from my manuscripts.

This abstract, which I now publish, must necessarily be imperfect. I

cannot 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 may have crept in, though I hope I have always been

cautious in trusting to good authorities alone. I can here give only

the general conclusions at which I have arrived, with a few facts in

illustration, but which, I hope, in most cases will suffice. No one can

feel more sensible than I do of the necessity of hereafter publishing

in detail all the facts, with references, on which my conclusions have

been grounded; and I hope in a future work to do this. For I am well

aware that scarcely a single point is discussed in this volume on which

facts cannot be adduced, often apparently leading to conclusions

directly opposite to those at which I have arrived. A fair result can

be obtained only by fully stating and balancing the facts and arguments

on both sides of each question; and this is here impossible.

I much regret that want of space prevents my having the satisfaction of

acknowledging the generous assistance which I have received from very

many naturalists, some of them personally unknown to me. I cannot,

however, let this opportunity pass without expressing my deep

obligations to Dr. Hooker, who, for the last fifteen years, has aided

me in every possible way by his large stores of knowledge and his

excellent judgment.

In considering the origin of species, it is quite conceivable that a

naturalist, reflecting on the mutual affinities of organic beings, on

their embryological relations, their geographical distribution,

geological succession, and other such facts, might come to the

conclusion that 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 shown how the innumerable species, inhabiting this world have

been modified, so as to acquire that perfection of structure and

coadaptation which justly excites our admiration. Naturalists

continually refer to external conditions, such as climate, food, &c.,

as the only possible cause of variation. In one limited sense, as we

shall hereafter see, this may be true; but it is preposterous to

attribute to mere external conditions, the structure, for instance, of

the woodpecker, with its feet, tail, beak, and tongue, so admirably

adapted to catch insects under the bark of trees. In the case of the

mistletoe, which draws its nourishment from certain trees, which has

seeds that must be transported by certain birds, and which has flowers

with separate sexes absolutely requiring the 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 of

external conditions, or of habit, or of the volition of the plant

itself.

It is, therefore, of the highest importance to gain a clear insight

into the means of modification and coadaptation. At the commencement of

my observations it seemed to me probable that a careful study of

domesticated animals and of cultivated plants would offer the best

chance of making out this obscure problem. Nor have I been

disappointed; in this and in all other perplexing cases I have

invariably found that our knowledge, imperfect though it be, of

variation under domestication, afforded the best and safest clue. I may

venture to express my conviction of the high value of such studies,

although they have been very commonly neglected by naturalists.

From these considerations, I shall devote the first chapter of this

abstract to variation under domestication. We shall thus see that a

large amount of hereditary modification is at least possible; and, what

is equally or more important, we shall see how great is the power of

man in accumulating by his selection successive slight variations. I

will then 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 can be treated properly only by giving long catalogues

of facts. We shall, however, be enabled to discuss what circumstances

are most favourable to variation. In the next chapter the struggle for

existence among all organic beings throughout the world, which

inevitably follows from the high geometrical ratio of their increase,

will be considered. This is the doctrine of Malthus, applied to the

whole animal and vegetable kingdoms. As many more individuals of each

species are born than can possibly survive; and as, consequently, there

is a frequently recurring struggle for existence, it follows that any

being, if it vary however slightly in any manner profitable to itself,

under the complex and sometimes varying conditions of life, will have a

better chance of surviving, and thus be _naturally selected_. From the

strong principle of inheritance, any selected variety will tend to

propagate its new and modified form.

This fundamental subject of natural selection will be treated at some

length in the fourth chapter; and we shall then see how natural

selection almost inevitably causes much extinction of the less improved

forms of life, and leads to what I have called divergence of character.

In the next chapter I shall discuss the complex and little known laws

of variation. In the five succeeding chapters, the most apparent and

gravest difficulties in accepting the theory will be given: namely,

first, the difficulties of transitions, or how a simple being or a

simple organ can be changed and perfected into a highly developed being

or into an elaborately constructed organ; secondly the subject of

instinct, or the mental powers of animals; thirdly, hybridism, or the

infertility of species and the fertility of varieties when

intercrossed; and fourthly, the imperfection of the geological record.

In the next chapter I shall consider the geological succession of

organic beings throughout time; in the twelfth and thirteenth, their

geographical distribution throughout space; in the fourteenth, their

classification or mutual affinities, both when mature and in an

embryonic condition. In the last chapter I shall give a brief

recapitulation of the whole work, and a few concluding remarks.

No one ought to feel surprise at much remaining as yet unexplained in

regard to the origin of species and varieties, if he make due allowance

for our profound ignorance in regard to the mutual relations of the

many beings which live around us. Who can explain why one species

ranges widely and is very numerous, and why another allied species has

a narrow range and is rare? Yet these relations are of the highest

importance, 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

inhabitants of the world during the many past geological epochs in its

history. Although much remains obscure, and will long remain obscure, I

can entertain no doubt, after the most deliberate study and

dispassionate judgment of which I am capable, that the view which most

naturalists until recently entertained, and which I formerly

entertained—namely, that each species has been independently created—is

erroneous. I am fully convinced that species are not immutable; but

that those belonging to what are called the same genera are lineal

descendants of some other and generally extinct species, in the same

manner as the acknowledged varieties of any one species are the

descendants of that species. Furthermore, I am convinced that natural

selection has been the most important, but not the exclusive, means of

modification.

CHAPTER I.

VARIATION UNDER DOMESTICATION.

Causes of Variability—Effects of Habit and the use and disuse of

Parts—Correlated Variation—Inheritance—Character of Domestic

Varieties—Difficulty of distinguishing between Varieties and

Species—Origin of Domestic Varieties from one or more Species—Domestic

Pigeons, their Differences and Origin—Principles of Selection,

anciently followed, their Effects—Methodical and Unconscious

Selection—Unknown Origin of our Domestic Productions—Circumstances

favourable to Man’s power of Selection.

_Causes of Variability._

When we compare the individuals of the same variety or sub-variety of

our older cultivated plants and animals, one of the first points which

strikes us is, that they generally differ more from each other than do

the individuals of any one species or variety in a state of nature. And

if we reflect on the vast diversity of the plants and animals which

have been cultivated, and which have varied during all ages under the

most different climates and treatment, we are driven to conclude that

this great variability is due to our domestic productions having been

raised under conditions of life not so uniform as, and somewhat

different from, those to which the parent species had been exposed

under nature. There is, also, some probability in the view propounded

by Andrew Knight, that this variability may be partly connected with

excess of food. It seems clear that organic beings must be exposed

during several generations to new conditions to cause any great amount

of variation; and that, when the organisation has once begun to vary,

it generally continues varying for many generations. No case is on

record of a variable organism ceasing to vary under cultivation. Our

oldest cultivated plants, such as wheat, still yield new varieties: our

oldest domesticated animals are still capable of rapid improvement or

modification.

As far as I am able to judge, after long attending to the subject, the

conditions of life appear to act in two ways—directly on the whole

organisation or on certain parts alone and in directly by affecting the

reproductive system. With respect to the direct action, we must bear in

mind that in every case, as Professor Weismann has lately insisted, and

as I have incidently shown in my work on “Variation under

Domestication,” there are two factors: namely, the nature of the

organism and the nature of the conditions. The former seems to be much

the more important; for nearly similar variations sometimes arise

under, as far as we can judge, dissimilar conditions; and, on the other

hand, dissimilar variations arise under conditions which appear to be

nearly uniform. The effects on the offspring are either definite or in

definite. They may be considered as definite when all or nearly all the

offspring of individuals exposed to certain conditions during several

generations are modified in the same manner. It is extremely difficult

to come to any conclusion in regard to the extent of the changes which

have been thus definitely induced. There can, however, be little doubt

about many slight changes, such as size from the amount of food, colour

from the nature of the food, thickness of the skin and hair from

climate, &c. Each of the endless variations which we see in the plumage

of our fowls must have had some efficient cause; and if the same cause

were to act uniformly during a long series of generations on many

individuals, all probably would be modified in the same manner. Such

facts as the complex and extraordinary out growths which variably

follow from the insertion of a minute drop of poison by a

gall-producing insect, shows us what singular modifications might

result in the case of plants from a chemical change in the nature of

the sap.

In definite variability is a much more common result of changed

conditions than definite variability, and has probably played a more

important part in the formation of our domestic races. We see in

definite variability in the endless slight peculiarities which

distinguish the individuals of the same species, and which cannot be

accounted for by inheritance from either parent or from some more

remote ancestor. Even strongly-marked differences occasionally appear

in the young of the same litter, and in seedlings from the same

seed-capsule. At long intervals of time, out of millions of individuals

reared in the same country and fed on nearly the same food, deviations

of structure so strongly pronounced as to deserve to be called

monstrosities arise; but monstrosities cannot be separated by any

distinct line from slighter variations. All such changes of structure,

whether extremely slight or strongly marked, which appear among many

individuals living together, may be considered as the in definite

effects of the conditions of life on each individual organism, in

nearly the same manner as the chill effects different men in an in

definite manner, according to their state of body or constitution,

causing coughs or colds, rheumatism, or inflammation of various organs.

With respect to what I have called the in direct action of changed

conditions, namely, through the reproductive system of being affected,

we may infer that variability is thus induced, partly from the fact of

this system being extremely sensitive to any change in the conditions,

and partly from the similarity, as Kölreuter and others have remarked,

between the variability which follows from the crossing of distinct

species, and that which may be observed with plants and animals when

reared under new or unnatural conditions. Many facts clearly show how

eminently susceptible the reproductive system is to very slight changes

in the surrounding conditions. Nothing is more easy than to tame an

animal, and few things more difficult than to get it to breed freely

under confinement, even when the male and female unite. How many

animals there are which will not breed, though kept in an almost free

state in their native country! This is generally, but erroneously

attributed to vitiated instincts. Many cultivated plants display the

utmost vigour, and yet rarely or never seed! In some few cases it has

been discovered that a very trifling change, such as a little more or

less water at some particular period of growth, will determine whether

or not a plant will produce seeds. I cannot here give the details which

I have collected and elsewhere published on this curious subject; but

to show how singular the laws are which determine the reproduction of

animals under confinement, I may mention that carnivorous animals, even

from the tropics, breed in this country pretty freely under

confinement, with the exception of the plantigrades or bear family,

which seldom produce young; whereas, carnivorous birds, with the rarest

exception, hardly ever lay fertile eggs. Many exotic plants have pollen

utterly worthless, in the same condition as in the most sterile

hybrids. When, on the one hand, we see domesticated animals and plants,

though often weak and sickly, breeding freely under confinement; and

when, on the other hand, we see individuals, though taken young from a

state of nature perfectly tamed, long-lived, and healthy (of which I

could give numerous instances), yet having their reproductive system so

seriously affected by unperceived causes as to fail to act, we need not

be surprised at this system, when it does act under confinement, acting

irregularly, and producing offspring somewhat unlike their parents. I

may add that as some organisms breed freely under the most unnatural

conditions—for instance, rabbits and ferrets kept in hutches—showing

that their reproductive organs are not easily affected; so will some

animals and plants withstand domestication or cultivation, and vary

very slightly—perhaps hardly more than in a state of nature.

Some naturalists have maintained that all variations are connected with

the act of sexual reproduction; but this is certainly an error; for I

have given in another work a long list of “sporting plants;” as they

are called by gardeners; that is, of plants which have suddenly

produced a single bud with a new and sometimes widely different

character from that of the other buds on the same plant. These bud

variations, as they may be named, can be propagated by grafts, offsets,

&c., and sometimes by seed. They occur rarely under nature, but are far

from rare under culture. As a single bud out of many thousands produced

year after year on the same tree under uniform conditions, has been

known suddenly to assume a new character; and as buds on distinct

trees, growing under different conditions, have sometimes yielded

nearly the same variety—for instance, buds on peach-trees producing

nectarines, and buds on common roses producing moss-roses—we clearly

see that the nature of the conditions is of subordinate importance in

comparison with the nature of the organism in determining each

particular form of variation; perhaps of not more importance than the

nature of the spark, by which a mass of combustible matter is ignited,

has in determining the nature of the flames.

_Effects of Habit and of the Use or Disuse of Parts; Correlated

Variation; Inheritance._

Changed habits produce an inherited effect as in the period of the

flowering of plants when transported from one climate to another. With

animals the increased use or disuse of parts has had a more marked

influence; thus I find in the domestic duck that the bones of the wing

weigh less and the bones of the leg more, in proportion to the whole

skeleton, than do the same bones in the wild duck; and this change may

be safely attributed to the domestic duck flying much less, and walking

more, than its wild parents. The great and inherited development of the

udders in cows and goats in countries where they are habitually milked,

in comparison with these organs in other countries, is probably another

instance of the effects of use. Not one of our domestic animals can be

named which has not in some country drooping ears; and the view which

has been suggested that the drooping is due to disuse of the muscles of

the ear, from the animals being seldom much alarmed, seems probable.

Many laws regulate variation, some few of which can be dimly seen, and

will hereafter be briefly discussed. I will here only allude to what

may be called correlated variation. Important changes in the embryo or

larva will probably entail changes in the mature animal. In

monstrosities, the correlations between quite distinct parts are very

curious; and many instances are given in Isidore Geoffroy St. Hilaire’s

great work on this subject. Breeders believe that long limbs are almost

always accompanied by an elongated head. Some instances of correlation

are quite whimsical; thus cats which are entirely white and have blue

eyes are generally deaf; but it has been lately stated by Mr. Tait that

this is confined to the males. Colour and constitutional peculiarities

go together, of which many remarkable cases could be given among

animals and plants. From facts collected by Heusinger, it appears that

white sheep and pigs are injured by certain plants, while dark-coloured

individuals escape: Professor Wyman has recently communicated to me a

good illustration of this fact; on asking some farmers in Virginia how

it was that all their pigs were black, they informed him that the pigs

ate the paint-root (Lachnanthes), which coloured their bones pink, and

which caused the hoofs of all but the black varieties to drop off; and

one of the “crackers” (_i.e._ Virginia squatters) added, “we select the

black members of a litter for raising, as they alone have a good chance

of living.” 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 between their outer toes;

pigeons with short beaks have small feet, and those with long beaks

large feet. Hence if man goes on selecting, and thus augmenting, any

peculiarity, he will almost certainly modify unintentionally other

parts of the structure, owing to the mysterious laws of correlation.

The results of the various, unknown, or but dimly understood laws of

variation are infinitely complex and diversified. It is well worth

while carefully to study the several treatises on some of our old

cultivated plants, as on the hyacinth, potato, even the dahlia, &c.;

and it is really surprising to note the endless points of structure and

constitution in which the varieties and sub-varieties differ slightly

from each other. The whole organisation seems to have become plastic,

and departs in a slight degree from that of the parental type.

Any variation which is not inherited is unimportant for us. But the

number and diversity of inheritable deviations of structure, both those

of slight and those of considerable physiological importance, are

endless. Dr. Prosper Lucas’ treatise, in two large volumes, is the

fullest and the best on this subject. No breeder doubts how strong is

the tendency to inheritance; that like produces like is his fundamental

belief: doubts have been thrown on this principle only by theoretical

writers. When any deviation of structure often appears, and we see it

in the father and child, we cannot tell whether it may not be due to

the same cause having acted on both; but when among individuals,

apparently exposed to the same conditions, any very rare deviation, due

to some extraordinary combination of circumstances, appears in the

parent—say, once among several million individuals—and it reappears in

the child, the mere doctrine of chances almost compels us to attribute

its reappearance to inheritance. Every one must have heard of cases of

albinism, prickly skin, hairy bodies, &c., appearing in several members

of the same family. If strange and rare deviations of structure are

truly inherited, less strange and commoner deviations may be freely

admitted to be inheritable. Perhaps the correct way of viewing the

whole subject would be, to look at the inheritance of every character

whatever as the rule, and non-inheritance as the anomaly.

The laws governing inheritance are for the most part unknown; no one

can say why the same peculiarity in different individuals of the same

species, or in different species, is sometimes inherited and sometimes

not so; why the child often reverts in certain characteristics to its

grandfather or grandmother or more remote ancestor; why a peculiarity

is often transmitted from one sex to both sexes, or to one sex alone,

more commonly but not exclusively to the like sex. It is a fact of some

importance to us, that peculiarities appearing in the males of our

domestic breeds are often transmitted, either exclusively or in a much

greater degree, to the males alone. A much more important rule, which I

think may be trusted, is that, at whatever period of life a peculiarity

first appears, it tends to reappear in the offspring at a corresponding

age, though sometimes earlier. In many cases this could not be

otherwise; thus the inherited peculiarities in the horns of cattle

could appear only in the offspring when nearly mature; peculiarities in

the silk-worm are known to appear at the corresponding caterpillar or

cocoon stage. But hereditary diseases and some other facts make me

believe that the rule has a wider extension, and that, when there is no

apparent reason why a peculiarity should appear at any particular age,

yet that it does tend to appear in the offspring at the same period at

which it first appeared in the parent. I believe this rule to be of the

highest importance in explaining the laws of embryology. These remarks

are of course confined to the first _appearance_ of the peculiarity,

and not to the primary cause which may have acted on the ovules or on

the male element; in nearly the same manner as the increased length of

the horns in the offspring from a short-horned cow by a long-horned

bull, though appearing late in life, is clearly due to the male

element.

Having alluded to the subject of reversion, I may here refer to a

statement often made by naturalists—namely, that our domestic

varieties, when run wild, gradually but invariably revert in character

to their aboriginal stocks. Hence it has been argued that no deductions

can be drawn from domestic races to species in a state of nature. I

have in vain endeavoured to discover on what decisive facts the above

statement has so often and so boldly been made. There would be great

difficulty in proving its truth: we may safely conclude that very many

of the most strongly marked domestic varieties could not possibly live

in a wild state. In many cases we do not know what the aboriginal stock

was, and so could not tell whether or not nearly perfect reversion had

ensued. It would be necessary, in order to prevent the effects of

intercrossing, that only a single variety should be turned loose in its

new home. Nevertheless, as our varieties certainly do occasionally

revert in some of their characters to ancestral forms, it seems to me

not improbable that if we could succeed in naturalising, or were to

cultivate, during many generations, the several races, for instance, of

the cabbage, in very poor soil—in which case, however, some effect

would have to be attributed to the _definite_ action of the poor

soil—that they would, to a large extent, or even wholly, revert to the

wild aboriginal stock. Whether or not the experiment would succeed is

not of great importance for our line of argument; for by the experiment

itself the conditions of life are changed. If it could be shown that

our domestic varieties manifested a strong tendency to reversion—that

is, to lose their acquired characters, while kept under the same

conditions and while kept in a considerable body, so that free

intercrossing might check, by blending together, any slight deviations

in their structure, in such case, I grant that we could deduce nothing

from domestic varieties in regard to species. But there is not a shadow

of evidence in favour of this view: to assert that we could not breed

our cart and race-horses, long and short-horned cattle, and poultry of

various breeds, and esculent vegetables, for an unlimited number of

generations, would be opposed to all experience.

_Character of Domestic Varieties; difficulty of distinguishing between

Varieties and Species; origin of Domestic Varieties from one or more

Species._

When we look to the hereditary varieties or races of our domestic

animals and plants, and compare them with closely allied species, we

generally perceive in each domestic race, as already remarked, less

uniformity of character than in true species. Domestic races often have

a somewhat monstrous character; by which I mean, that, although

differing from each other and from other species of the same genus, in

several trifling respects, they often differ in an extreme degree in

some one part, both when compared one with another, and more especially

when compared with the species under nature to which they are nearest

allied. With these exceptions (and with that of the perfect fertility

of varieties when crossed—a subject hereafter to be discussed),

domestic races of the same species differ from each other in the same

manner as do the closely allied species of the same genus in a state of

nature, but the differences in most cases are less in degree. This must

be admitted as true, for the domestic races of many animals and plants

have been ranked by some competent judges as the descendants of

aboriginally distinct species, and by other competent judges as mere

varieties. If any well marked distinction existed between a domestic

race and a species, this source of doubt would not so perpetually

recur. It has often been stated that domestic races do not differ from

each other in characters of generic value. It can be shown that this

statement is not correct; but naturalists differ much in determining

what characters are of generic value; all such valuations being at

present empirical. When it is explained how genera originate under

nature, it will be seen that we have no right to expect often to find a

generic amount of difference in our domesticated races.

In attempting to estimate the amount of structural difference between

allied domestic races, we are soon involved in doubt, from not knowing

whether they are descended from one or several parent species. This

point, if it could be cleared up, would be interesting; if, for

instance, it could be shown that the greyhound, bloodhound, terrier,

spaniel and bull-dog, which we all know propagate their kind truly,

were the offspring of any single species, then such facts would have

great weight in making us doubt about the immutability of the many

closely allied natural species—for instance, of the many

foxes—inhabiting the different quarters of the world. I do not believe,

as we shall presently see, that the whole amount of difference between

the several breeds of the dog has been produced under domestication; I

believe that a small part of the difference is due to their being

descended from distinct species. In the case of strongly marked races

of some other domesticated species, there is presumptive or even strong

evidence that all are descended from a single wild stock.

It has often been assumed that man has chosen for domestication animals

and plants having an extraordinary inherent tendency to vary, and

likewise to withstand diverse climates. I do not dispute that these

capacities have added largely to the value of most of our domesticated

productions; but how could a savage possibly know, when he first tamed

an animal, whether it would vary in succeeding generations, and whether

it would endure other climates? Has the little variability of the ass

and goose, or the small power of endurance of warmth by the reindeer,

or of cold by the common camel, prevented their domestication? I cannot

doubt that if other animals and plants, equal in number to our

domesticated productions, and belonging to equally diverse classes and

countries, were taken from a state of nature, and could be made to

breed for an equal number of generations under domestication, they

would on an average vary as largely as the parent species of our

existing domesticated productions have varied.

In the case of most of our anciently domesticated animals and plants,

it is not possible to come to any definite conclusion, whether they are

descended from one or several wild species. The argument mainly relied

on by those who believe in the multiple origin of our domestic animals

is, that we find in the most ancient times, on the monuments of Egypt,

and in the lake-habitations of Switzerland, much diversity in the

breeds; and that some of these ancient breeds closely resemble, or are

even identical with, those still existing. But this only throws far

backward the history of civilisation, and shows that animals were

domesticated at a much earlier period than has hitherto been supposed.

The lake-inhabitants of Switzerland cultivated several kinds of wheat

and barley, the pea, the poppy for oil and flax; and they possessed

several domesticated animals. They also carried on commerce with other

nations. All this clearly shows, as Heer has remarked, that they had at

this early age progressed considerably in civilisation; and this again

implies a long continued previous period of less advanced civilisation,

during which the domesticated animals, kept by different tribes in

different districts, might have varied and given rise to distinct

races. Since the discovery of flint tools in the superficial formations

of many parts of the world, all geologists believe that barbarian men

existed at an enormously remote period; and we know that at the present

day there is hardly a tribe so barbarous as not to have domesticated at

least the dog.

The origin of most of our domestic animals will probably forever remain

vague. But I may here state that, looking to the domestic dogs of the

whole world, I have, after a laborious collection of all known facts,

come to the conclusion that several wild species of Canidæ have been

tamed, and that their blood, in some cases mingled together, flows in

the veins of our domestic breeds. In regard to sheep and goats I can

form no decided opinion. From facts communicated to me by Mr. Blyth, on

the habits, voice, constitution and structure of the humped Indian

cattle, it is almost certain that they are descended from a different

aboriginal stock from our European cattle; and some competent judges

believe that these latter have had two or three wild progenitors,

whether or not these deserve to be called species. This conclusion, as

well as that of the specific distinction between the humped and common

cattle, may, indeed, be looked upon as established by the admirable

researches of Professor Rütimeyer. With respect to horses, from reasons

which I cannot here give, I am doubtfully inclined to believe, in

opposition to several authors, that all the races belong to the same

species. Having kept nearly all the English breeds of the fowl alive,

having bred and crossed them, and examined their skeletons, it appears

to me almost certain that all are the descendants of the wild Indian

fowl, Gallus bankiva; and this is the conclusion of Mr. Blyth, and of

others who have studied this bird in India. In regard to ducks and

rabbits, some breeds of which differ much from each other, the evidence

is clear that they are all descended from the common duck and wild

rabbit.

The doctrine of the origin of our several domestic races from several

aboriginal stocks, has been carried to an absurd extreme by some

authors. They believe that every race which breeds true, let the

distinctive characters be ever so slight, has had its wild prototype.

At this rate there must have existed at least a score of species of

wild cattle, as many sheep, and several goats, in Europe alone, and

several even within Great Britain. One author believes that there

formerly existed eleven wild species of sheep peculiar to Great

Britain! When we bear in mind that Britain has now not one peculiar

mammal, and France but few distinct from those of Germany, and so with

Hungary, Spain, &c., but that each of these kingdoms possesses several

peculiar breeds of cattle, sheep, &c., we must admit that many domestic

breeds must have originated in Europe; for whence otherwise could they

have been derived? So it is in India. Even in the case of the breeds of

the domestic dog throughout the world, which I admit are descended from

several wild species, it cannot be doubted that there has been an

immense amount of inherited variation; for who will believe that

animals closely resembling the Italian greyhound, the bloodhound, the

bull-dog, pug-dog, or Blenheim spaniel, &c.—so unlike all wild

Canidæ—ever existed in a state of nature? It has often been loosely

said that all our races of dogs have been produced by the crossing of a

few aboriginal species; but by crossing we can only get forms in some

degree intermediate between their parents; and if we account for our

several domestic races by this process, we must admit the former

existence of the most extreme forms, as the Italian greyhound,

bloodhound, bull-dog, &c., in the wild state. Moreover, the possibility

of making distinct races by crossing has been greatly exaggerated. Many

cases are on record showing that a race may be modified by occasional

crosses if aided by the careful selection of the individuals which

present the desired character; but to obtain a race intermediate

between two quite distinct races would be very difficult. Sir J.

Sebright expressly experimented with this object and failed. The

offspring from the first cross between two pure breeds is tolerably and

sometimes (as I have found with pigeons) quite uniform in character,

and every thing seems simple enough; but when these mongrels are

crossed one with another for several generations, hardly two of them

are alike, and then the difficulty of the task becomes manifest.

_Breeds of the Domestic Pigeon, their Differences and Origin._

Believing that it is always best to study some special group, I have,

after deliberation, taken up domestic pigeons. I have kept every breed

which I could purchase or obtain, and have been most kindly favoured

with skins from several quarters of the world, more especially by the

Hon. W. Elliot from India, and by the Hon. C. Murray from Persia. Many

treatises in different languages have been published on pigeons, and

some of them are very important, as being of considerable antiquity. I

have associated with several eminent fanciers, and have been permitted

to join two of the London Pigeon Clubs. The diversity of the breeds is

something astonishing. Compare the English carrier and the short-faced

tumbler, and see the wonderful difference in their beaks, entailing

corresponding differences in their skulls. The carrier, more especially

the male bird, is also remarkable from the wonderful development of the

carunculated skin about the head, and this is accompanied by greatly

elongated eyelids, very large external orifices to the nostrils, and a

wide gape of mouth. The short-faced tumbler has a beak in outline

almost like that of a finch; and the common tumbler has the singular

inherited habit of flying at a great height in a compact flock, and

tumbling in 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

have very long necks, others very long wings and tails, others

singularly short tails. The barb is allied to the carrier, but, instead

of a long beak, has a very short and broad one. The pouter has a much

elongated body, wings, and legs; and its enormously developed crop,

which it glories in inflating, may well excite astonishment and even

laughter. The turbit has a short and conical beak, with a line of

reversed feathers down the breast; and it has the habit of continually

expanding, slightly, the upper part of the œsophagus. The Jacobin has

the feathers so much reversed along the back of the neck that they form

a hood, and it has, proportionally to its size, elongated wing and tail

feathers. The trumpeter and laugher, as their names express, utter a

very different coo from the other breeds. The fantail has thirty or

even forty tail-feathers, instead of twelve or fourteen, the normal

number in all the members of the great pigeon family: these feathers

are kept expanded and are carried so erect that in good birds the head

and tail touch: the oil-gland is quite aborted. Several other less

distinct breeds might be specified.

In the skeletons of the several breeds, the development of the bones of

the face, in length and breadth and curvature, differs enormously. The

shape, as well as the breadth and length of the ramus of the lower jaw,

varies in a highly remarkable manner. The caudal and sacral vertebræ

vary in number; as does the number of the ribs, together with their

relative breadth and the presence of processes. The size and shape of

the apertures in the sternum are highly variable; so is the degree of

divergence and relative size of the two arms of the furcula. The

proportional width of the gape of mouth, the proportional length of the

eyelids, of the orifice of the nostrils, of the tongue (not always in

strict correlation with the length of beak), the size of the crop and

of the upper part of the œsophagus; the development and abortion of the

oil-gland; the number of the primary wing and caudal feathers; the

relative length of the wing and tail to each other and to the body; the

relative length of the leg and foot; the number of scutellæ on the

toes, the development of skin between the toes, are all points of

structure which are variable. The period at which the perfect plumage

is acquired varies, as does the state of the down with which the

nestling birds are clothed when hatched. The shape and size of the eggs

vary. The manner of flight, and in some breeds the voice and

disposition, differ remarkably. Lastly, in certain breeds, the males

and females have come to differ in a slight degree from each other.

Altogether at least a score of pigeons might be chosen, which, if shown

to an ornithologist, and he were told that they were wild birds, would

certainly be ranked by him as well-defined species. Moreover, I do not

believe that any ornithologist would in this case place the English

carrier, the short-faced tumbler, the runt, the barb, pouter, and

fantail in the same genus; more especially as in each of these breeds

several truly-inherited sub-breeds, or species, as he would call them,

could be shown him.

Great as are the differences between the breeds of the pigeon, I am

fully convinced that the common opinion of naturalists is correct,

namely, that all are 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

of the reasons which have led me to this belief are in some degree

applicable in other cases, I will here briefly give them. If the

several breeds are not varieties, and have not proceeded from the

rock-pigeon, they must have descended from at least seven or eight

aboriginal stocks; for it is impossible to make the present domestic

breeds by the crossing of any lesser number: how, for instance, could a

pouter be produced by crossing two breeds unless one of the

parent-stocks possessed the characteristic enormous crop? The supposed

aboriginal stocks must all have been rock-pigeons, that is, they did

not breed or willingly perch on trees. But besides C. livia, with its

geographical sub-species, only two or three other species of

rock-pigeons are known; and these have not any of the characters of the

domestic breeds. Hence the supposed aboriginal stocks must either still

exist in the countries where they were originally domesticated, and yet

be unknown to ornithologists; and this, considering their size, habits

and remarkable characters, seems improbable; or they must have become

extinct in the wild state. But birds breeding on precipices, and good

flyers, are unlikely to be exterminated; and the common rock-pigeon,

which has the same habits with the domestic breeds, has not been

exterminated even on several of the smaller British islets, or on the

shores of the Mediterranean. Hence the supposed extermination of so

many species having similar habits with the rock-pigeon seems a very

rash assumption. Moreover, the several above-named domesticated breeds

have been transported to all parts of the world, and, therefore, some

of them must have been carried back again into their native country;

but not one has become wild or feral, though the dovecot-pigeon, which

is the rock-pigeon in a very slightly altered state, has become feral

in several places. Again, all recent experience shows that it is

difficult to get wild animals to breed freely under domestication; yet

on the hypothesis of the multiple origin of our pigeons, it must be

assumed that at least seven or eight species were so thoroughly

domesticated in ancient times by half-civilized man, as to be quite

prolific under confinement.

An argument of great weight, and applicable in several other cases, is,

that the above-specified breeds, though agreeing generally with the

wild rock-pigeon in constitution, habits, voice, colouring, and in most

parts of their structure, yet are certainly highly abnormal in other

parts; we may look in vain through the whole great family of Columbidæ

for a beak like that of the English carrier, or that of the short-faced

tumbler, or barb; for reversed feathers like those of the Jacobin; for

a crop like that of the pouter; for tail-feathers like those of the

fantail. Hence it must be assumed, not only that half-civilized man

succeeded in thoroughly domesticating several species, but that he

intentionally or by chance picked out extraordinarily abnormal species;

and further, that these very species have since all become extinct or

unknown. So many strange contingencies are improbable in the highest

degree.

Some facts in regard to the colouring of pigeons well deserve

consideration. The rock-pigeon is of a slaty-blue, with white loins;

but the Indian sub-species, C. intermedia of Strickland, has this part

bluish. The tail has a terminal dark bar, with the outer feathers

externally edged at the base with white. The wings have two black bars.

Some semi-domestic breeds, and some truly wild breeds, have, besides

the two black bars, the wings chequered with black. These several marks

do not occur together in any other species of the whole family. Now, in

every one of the domestic breeds, taking thoroughly well-bred birds,

all the above marks, even to the white edging of the outer

tail-feathers, sometimes concur perfectly developed. Moreover, when

birds belonging to two or more distinct breeds are crossed, none of

which are blue or have any of the above-specified marks, the mongrel

offspring are very apt suddenly to acquire these characters. To give

one instance out of several which I have observed: I crossed some white

fantails, which breed very true, with some black barbs—and it so

happens that blue varieties of barbs are so rare that I never heard of

an instance in England; and the mongrels were black, brown and mottled.

I also crossed a barb with a spot, which is a white bird with a red

tail and red spot on the forehead, and which notoriously breeds very

true; the mongrels were dusky and mottled. I then crossed one of the

mongrel barb-fantails with a mongrel barb-spot, and they produced a

bird of as beautiful a blue colour, with the white loins, double black

wing-bar, and barred and white-edged tail-feathers, as any wild

rock-pigeon! We can understand these facts, on the well-known principle

of reversion to ancestral characters, if all the domestic breeds are

descended from the rock-pigeon. But if we deny this, we must make one

of the two following highly improbable suppositions. Either, first,

that all the several imagined aboriginal stocks were coloured and

marked like the rock-pigeon, although no other existing species is thus

coloured and marked, so that in each separate breed there might be a

tendency to revert to the very same colours and markings. Or, secondly,

that each breed, even the purest, has within a dozen, or at most within

a score, of generations, been crossed by the rock-pigeon: I say within

a dozen or twenty generations, for no instance is known of crossed

descendants reverting to an ancestor of foreign blood, removed by a

greater number of generations. In a breed which has been crossed only

once the tendency to revert to any character derived from such a cross

will naturally become less and less, as in each succeeding generation

there will be less of the foreign blood; but when there has been no

cross, and there is a tendency in the breed to revert to a character

which was lost during some former generation, this tendency, for all

that we can see to the contrary, may be transmitted undiminished for an

indefinite number of generations. These two distinct cases of reversion

are often confounded together by those who have written on inheritance.

Lastly, the hybrids or mongrels from between all the breeds of the

pigeon are perfectly fertile, as I can state from my own observations,

purposely made, on the most distinct breeds. Now, hardly any cases have

been ascertained with certainty of hybrids from two quite distinct

species of animals being perfectly fertile. Some authors believe that

long-continued domestication eliminates this strong tendency to

sterility in species. From the history of the dog, and of some other

domestic animals, this conclusion is probably quite correct, if applied

to species closely related to each other. But to extend it so far as to

suppose that species, aboriginally as distinct as carriers, tumblers,

pouters, and fantails now are, should yield offspring perfectly

fertile, _inter se_, seems to me rash in the extreme.

From these several reasons, namely, the improbability of man having

formerly made seven or eight supposed species of pigeons to breed

freely under domestication—these supposed species being quite unknown

in a wild state, and their not having become anywhere feral—these

species presenting certain very abnormal characters, as compared with

all other Columbidæ, though so like the rock-pigeon in most other

respects—the occasional reappearance of the blue colour and various

black marks in all the breeds, both when kept pure and when crossed—and

lastly, the mongrel offspring being perfectly fertile—from these

several reasons, taken together, we may safely conclude that all our

domestic breeds are descended from the rock-pigeon or Columba livia

with its geographical sub-species.

In favour of this view, I may add, firstly, that the wild C. livia has

been found capable of domestication in Europe and in India; and that it

agrees in habits and in a great number of points of structure with all

the domestic breeds. Secondly, that although an English carrier or a

short-faced tumbler differs immensely in certain characters from the

rock-pigeon, yet that by comparing the several sub-breeds of these two

races, more especially those brought from distant countries, we can

make, between them and the rock-pigeon, an almost perfect series; so we

can in some other cases, but not with all the breeds. Thirdly, those

characters which are mainly distinctive of each breed are in each

eminently variable, for instance, the wattle and length of beak of the

carrier, the shortness of that of the tumbler, and the number of

tail-feathers in the fantail; and the explanation of this fact will be

obvious when we treat of selection. Fourthly, pigeons have been watched

and tended with the utmost care, and loved by many people. They have

been domesticated for thousands of years in several quarters of the

world; the earliest known record of pigeons is in the fifth Ægyptian

dynasty, about 3000 B.C., as was pointed out to me by Professor

Lepsius; but Mr. Birch informs me that pigeons are given in a bill of

fare in the previous dynasty. In the time of the Romans, as we hear

from Pliny, immense prices were given for pigeons; “nay, they are come

to this pass, that they can reckon up their pedigree and race.” Pigeons

were much valued by Akber Khan in India, about the year 1600; never

less than 20,000 pigeons were taken with the court. “The monarchs 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 them astonishingly.” About

this same period the Dutch were as eager about pigeons as were the old

Romans. The paramount importance of these considerations in explaining

the immense amount of variation which pigeons have undergone, will

likewise be obvious when we treat of Selection. We shall then, also,

see how it is that the several breeds so often have a somewhat

monstrous character. It is also a most favourable circumstance for the

production of distinct breeds, that male and female pigeons can be

easily mated for life; and thus different breeds can be kept 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 and

watched the several kinds, well knowing how truly they breed, I felt

fully as much difficulty in believing that since they had been

domesticated they had all proceeded from a common parent, as any

naturalist could in coming to a similar conclusion in regard to the

many species of finches, or other groups of birds, in nature. One

circumstance has struck me much; namely, that nearly all the breeders

of the various domestic animals and the cultivators of plants, with

whom I have conversed, or whose treatises I have read, are firmly

convinced that the several breeds to which each has attended, are

descended from so many aboriginally distinct species. Ask, as I have

asked, a celebrated raiser of Hereford cattle, whether his cattle might

not have descended from Long-horns, or both from a common parent-stock,

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 main

breed was descended from a distinct species. Van Mons, in his treatise

on pears and apples, shows how utterly he disbelieves that the several

sorts, for instance a Ribston-pippin or Codlin-apple, could ever have

proceeded from the seeds of the same tree. Innumerable other examples

could be given. The explanation, I think, is simple: from

long-continued study they are strongly impressed with the differences

between the several races; and though they well know that each race

varies slightly, for they win their prizes by selecting such slight

differences, yet they ignore all general arguments, and refuse to sum

up in their minds slight differences accumulated during many successive

generations. May not those naturalists who, knowing far less of the

laws of inheritance than does the breeder, and knowing no more than he

does of the intermediate links in the long lines of descent, yet admit

that many of our domestic races are descended from the same parents—may

they not learn a lesson of caution, when they deride the idea of

species in a state of nature being lineal descendants of other species?

_Principles of Selection anciently followed, and their Effects._

Let us now briefly consider the steps by which domestic races have been

produced, either from one or from several allied species. Some effect

may be attributed to the direct and definite action of the external

conditions of life, and some to habit; but he would be a bold man who

would account by such agencies for the differences between a dray and

race-horse, a greyhound and bloodhound, a carrier and tumbler pigeon.

One of the most remarkable features in our domesticated races is that

we see in them adaptation, not indeed to the animal’s or plant’s own

good, but to man’s use or fancy. Some variations useful to him have

probably arisen suddenly, or by one step; many botanists, for instance,

believe that the fuller’s teasel, with its hooks, which can not be

rivalled by any mechanical contrivance, is only a variety of the wild

Dipsacus; and this amount of change may have suddenly arisen in a

seedling. So it has probably been with the turnspit dog; and this is

known to have been the case with the ancon sheep. But when we compare

the dray-horse and race-horse, the dromedary and camel, the various

breeds of sheep fitted either for cultivated land or mountain pasture,

with the wool of one breed good for one purpose, and that of another

breed for another purpose; when we compare the many breeds of dogs,

each good for man in different ways; when we compare the game-cock, so

pertinacious in battle, with other breeds so little quarrelsome, with

“everlasting layers” which never desire to sit, and with the bantam so

small and elegant; when we compare the host of agricultural, culinary,

orchard, and flower-garden races of plants, most useful to man at

different seasons and for different purposes, or so beautiful in his

eyes, we must, I think, look further than to mere variability. We can

not suppose that all the breeds were suddenly produced as perfect and

as useful as we now see them; indeed, in many cases, we know that this

has not been their history. The key is man’s power of accumulative

selection: nature gives successive variations; man adds them up in

certain directions useful to him. In this sense he may be said to have

made for himself useful breeds.

The great power of this principle of selection is not hypothetical. It

is certain that several of our eminent breeders have, even within a

single lifetime, modified to a large extent their breeds of cattle and

sheep. In order fully to realise what they have done it is almost

necessary to read several of the many treatises devoted to this

subject, and to inspect the animals. Breeders habitually speak of an

animal’s organisation as something plastic, which they can model almost

as they please. If I had space I could quote numerous passages to this

effect from highly competent authorities. Youatt, who was probably

better acquainted with the works of agriculturalists than almost any

other individual, and who was himself a very good judge of animals,

speaks of the principle of selection as “that which enables the

agriculturist, not only to modify the character of his flock, but to

change it altogether. It is the magician’s wand, by means of which he

may summon into life whatever form and mould he pleases.” Lord

Somerville, speaking of what breeders have done for sheep, says: “It

would seem as if they had chalked out upon a wall a form perfect in

itself, and then had given it existence.” In Saxony the importance of

the principle of selection in regard to merino sheep is so fully

recognised, that men follow it as a trade: the sheep are placed on a

table and are studied, like a picture by a connoisseur; this is done

three times at intervals of months, and the sheep are each time marked

and classed, so that the very best may ultimately be selected for

breeding.

What English breeders have actually effected is proved by the enormous

prices given for animals with a good pedigree; and these have been

exported to almost every quarter of the world. The improvement is by no

means generally due to crossing different breeds; all the best breeders

are strongly opposed to this practice, except sometimes among closely

allied sub-breeds. And when a cross has been made, the closest

selection is far more indispensable even than in ordinary cases. If

selection consisted merely in separating some very distinct variety and

breeding from it, the principle would be so obvious as hardly to be

worth notice; but its importance consists in the great effect produced

by the accumulation in one direction, during successive generations, of

differences absolutely inappreciable by an uneducated eye—differences

which I for one have vainly attempted to appreciate. Not one man in a

thousand has accuracy of eye and judgment sufficient to become an

eminent breeder. If gifted with these qualities, and he studies his

subject for years, and devotes his lifetime to it with indomitable

perseverance, he will succeed, and may make great improvements; if he

wants any of these qualities, he will assuredly fail. Few would readily

believe in the natural capacity and years of practice requisite to

become even a skilful pigeon-fancier.

The same principles are followed by horticulturists; but the variations

are here often more abrupt. No one supposes that our choicest

productions have been produced by a single variation from the

aboriginal stock. We have proofs that this is not so in several cases

in which exact records have been kept; thus, to give a very trifling

instance, the steadily-increasing size of the common gooseberry may be

quoted. We see an astonishing improvement in many florists’ flowers,

when the flowers of the present day are compared with drawings made

only twenty or thirty years ago. When a race of plants is once pretty

well established, the seed-raisers do not pick out the best plants, but

merely go over their seed-beds, and pull up the “rogues,” as they call

the plants that deviate from the proper standard. With animals this

kind of selection is, in fact, likewise followed; for hardly any one is

so careless as to breed from his worst animals.

In regard to plants, there is another means of observing the

accumulated effects of selection—namely, by comparing the diversity of

flowers in the different varieties of the same species in the

flower-garden; the diversity of leaves, pods, or tubers, or whatever

part is valued, in the kitchen-garden, in comparison with the flowers

of the same varieties; and the diversity of fruit of the same species

in the orchard, in comparison with the leaves and flowers of the same

set of varieties. See how different the leaves of the cabbage are, and

how extremely alike the flowers; how unlike the flowers of the

heartsease are, and how alike the leaves; how much the fruit of the

different kinds of gooseberries differ in size, colour, shape, and

hairiness, and yet the flowers present very slight differences. It is

not that the varieties which differ largely in some one point do not

differ at all in other points; this is hardly ever—I speak after

careful observation—perhaps never, the case. The law of correlated

variation, the importance of which should never be overlooked, will

ensure some differences; but, as a general rule, it cannot be doubted

that the continued selection of slight variations, either in the

leaves, the flowers, or the fruit, will produce races differing from

each other chiefly in these characters.

It may be objected that the principle of selection has been reduced to

methodical practice for scarcely more than three-quarters of a century;

it has certainly been more attended to of late years, and many

treatises have been published on the subject; and the result has been,

in a corresponding degree, rapid and important. But it is very far from

true that the principle is a modern discovery. I could give several

references to works of high antiquity, in which the full importance of

the principle is acknowledged. In rude and barbarous periods of English

history choice animals were often imported, and laws were passed to

prevent their exportation: the destruction of horses under a certain

size was ordered, and this may be compared to the “roguing” of plants

by nurserymen. The principle of selection I find distinctly given in an

ancient Chinese encyclopædia. Explicit rules are laid down by some of

the Roman classical writers. From passages in Genesis, it is clear that

the colour of domestic animals was at that early period attended to.

Savages now sometimes cross their dogs with wild canine animals, to

improve the breed, and they formerly did so, as is attested by passages

in Pliny. The savages in South Africa match their draught cattle by

colour, as do some of the Esquimaux their teams of dogs. Livingstone

states that good domestic breeds are highly valued by the negroes in

the interior of Africa who have not associated with Europeans. Some of

these facts do not show actual selection, but they show that the

breeding of domestic animals was carefully attended to in 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 breeding, for

the inheritance of good and bad qualities is so obvious.

_Unconscious Selection._

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 of the kind in the country. But, for our purpose, a form of

selection, which may be called unconscious, and which results from

every one trying to possess and breed from the best individual animals,

is more important. Thus, a man who intends keeping pointers naturally

tries to get as good dogs as he can, and afterwards breeds from his own

best dogs, but he has no wish or expectation of permanently altering

the breed. Nevertheless we may infer that this process, continued

during centuries, would improve and modify any breed, in the same way

as Bakewell, Collins, &c., by this very same process, only carried on

more methodically, did greatly modify, even during their lifetimes, the

forms and qualities of their cattle. Slow and insensible changes of

this kind could never be recognised unless actual measurements or

careful drawings of the breeds in question have been made long ago,

which may serve for comparison. In some cases, however, unchanged, or

but little changed, individuals of the same breed exist in less

civilised districts, where the breed has been less improved. There is

reason to believe that King Charles’ spaniel has been unconsciously

modified to a large extent since the time of that monarch. Some highly

competent authorities are convinced that the setter is directly derived

from the spaniel, and has probably been slowly altered from it. It is

known that the English pointer has been greatly changed within the last

century, and in this case the change has, it is believed, been chiefly

effected by crosses with the foxhound; but what concerns us is, that

the change has been effected unconsciously and gradually, and yet so

effectually that, though the old Spanish pointer certainly came from

Spain, Mr. Borrow has not seen, as I am informed by him, any native dog

in Spain like our pointer.

By a similar process of selection, and by careful training, English

race-horses have come to surpass in fleetness and size the parent

Arabs, so that the latter, by the regulations for the Goodwood Races,

are favoured in the weights which they carry. Lord Spencer and others

have shown how the cattle of England have increased in weight and in

early maturity, compared with the stock formerly kept in this country.

By comparing the accounts given in various old treatises of the former

and present state of carrier and tumbler pigeons in Britain, India, and

Persia, we can trace the stages through which they have insensibly

passed, and come to differ so greatly from the rock-pigeon.

Youatt gives an excellent illustration of the effects of a course of

selection which may be considered as unconscious, in so far that the

breeders could never have expected, or even wished, to produce the

result which ensued—namely, the production of the distinct strains. The

two flocks of Leicester sheep kept by Mr. Buckley and Mr. Burgess, as

Mr. Youatt remarks, “Have been purely bred from the original stock of

Mr. Bakewell for upwards of fifty years. There is not a suspicion

existing in the mind of any one at all acquainted with the subject that

the owner of either of them has deviated in any one instance from the

pure blood of Mr. Bakewell’s flock, and yet the difference between the

sheep possessed by these two gentlemen is so great that they have the

appearance of being quite different varieties.”

If there exist savages so barbarous as never to think of the inherited

character of the offspring of their domestic animals, yet any one

animal particularly useful to them, for any special purpose, would be

carefully preserved during famines and other accidents, to which

savages are so liable, and such choice animals would thus generally

leave more offspring than the inferior ones; so that in this case there

would be a kind of unconscious selection going on. We see the value set

on animals even by the barbarians of Tierra del Fuego, by their killing

and devouring their old women, in times of dearth, as of less value

than their dogs.

In plants the same gradual process of improvement through the

occasional preservation of the best individuals, whether or not

sufficiently distinct to be ranked at their first appearance as

distinct varieties, and whether or not two or more species or races

have become blended together by crossing, may plainly be recognised in

the increased size and beauty which we now see in the varieties of the

heartsease, rose, pelargonium, dahlia, and other plants, when compared

with the older varieties or with their parent-stocks. No one would ever

expect to get a first-rate heartsease or dahlia from the seed of a wild

plant. No one would expect to raise a first-rate melting pear from the

seed of a wild pear, though he might succeed from a poor seedling

growing wild, if it had come from a garden-stock. The pear, though

cultivated in classical times, appears, from Pliny’s description, to

have been a fruit of very inferior quality. I have seen great surprise

expressed in horticultural works at the wonderful skill of gardeners in

having produced such splendid results from such poor materials; but the

art has been simple, and, as far as the final result is concerned, has

been followed almost unconsciously. It has consisted in always

cultivating the best known variety, sowing its seeds, and, when a

slightly better variety chanced to appear, selecting it, and so

onwards. But the gardeners of the classical period, who cultivated the

best pears which they could procure, never thought what splendid fruit

we should eat; though we owe our excellent fruit in some small degree

to their having naturally chosen and preserved the best varieties they

could anywhere find.

A large amount of change, thus slowly and unconsciously accumulated,

explains, as I believe, the well-known fact, that in a number of cases

we cannot recognise, and therefore do not know, the wild parent-stocks

of the plants which have been longest cultivated in our flower and

kitchen gardens. If it has taken centuries or thousands of years to

improve or modify most of our plants up to their present standard of

usefulness to man, we can understand how it is that neither Australia,

the Cape of Good Hope, nor any other region inhabited by quite

uncivilised man, has afforded us a single plant worth culture. It is

not that these countries, so rich in species, do not by a strange

chance possess the aboriginal stocks of any useful plants, but that the

native plants have not been improved by continued selection up to a

standard of perfection comparable with that acquired by the plants in

countries anciently civilised.

In regard to the domestic animals kept by uncivilised man, it should

not be overlooked that they almost always have to struggle for their

own food, at least during certain seasons. And in two countries very

differently circumstanced, individuals of the same species, having

slightly different constitutions or structure, would often succeed

better in the one country than in the other, and thus by a process of

“natural selection,” as will hereafter be more fully explained, two

sub-breeds might be formed. This, perhaps, partly explains why the

varieties kept by savages, as has been remarked by some authors, have

more of the character of true species than the varieties kept in

civilised countries.

On the view here given of the important part which selection by man has

played, it becomes at once obvious, how it is that our domestic races

show adaptation in their structure or in their habits to man’s wants or

fancies. We can, I think, further understand the frequently abnormal

character of our domestic races, and likewise their differences being

so great in external characters, and relatively so slight in internal

parts or organs. Man can hardly select, or only with much difficulty,

any deviation of structure excepting such as is externally visible; and

indeed he rarely cares for what is internal. He can never act by

selection, excepting on variations which are first given to him in some

slight degree by nature. No man would ever try to make a fantail till

he saw a pigeon with a tail developed in some slight degree in an

unusual manner, or a pouter till he saw a pigeon with a crop of

somewhat unusual size; and the more abnormal or unusual any character

was when it first appeared, the more likely it would be to catch his

attention. But to use such an expression as trying to make a fantail

is, I have no doubt, in most cases, utterly incorrect. The man who

first selected a pigeon with a slightly larger tail, never dreamed what

the descendants of that pigeon would become through long-continued,

partly unconscious and partly methodical, selection. Perhaps the parent

bird of all fantails had only fourteen tail-feathers somewhat expanded,

like the present Java fantail, or like individuals of other and

distinct breeds, in which as many as seventeen tail-feathers have been

counted. Perhaps the first pouter-pigeon did not inflate its crop much

more than the turbit now does the upper part of its œsophagus—a habit

which is disregarded by all fanciers, as it is not one of the points of

the breed.

Nor let it be thought that some great deviation of structure would be

necessary to catch the fancier’s eye: he perceives extremely small

differences, and it is in human nature to value any novelty, however

slight, in one’s own possession. Nor must the value which would

formerly have been set on any slight differences in the individuals of

the same species, be judged of by the value which is now set on them,

after several breeds have fairly been established. It is known that

with pigeons many slight variations now occasionally appear, but these

are rejected as faults or deviations from the standard of perfection in

each breed. The common goose has not given rise to any marked

varieties; hence the Toulouse and the common breed, which differ only

in colour, that most fleeting of characters, have lately been exhibited

as distinct at our poultry-shows.

These views appear to explain what has sometimes been noticed, namely,

that we know hardly anything about the origin or history of any of our

domestic breeds. But, in fact, a breed, like a dialect of a language,

can hardly be said to have a distinct origin. A man preserves and

breeds from an individual with some slight deviation of structure, or

takes more care than usual in matching his best animals, and thus

improves them, and the improved animals slowly spread in the immediate

neighbourhood. But they will as yet hardly have a distinct name, and

from being only slightly valued, their history will have been

disregarded. When further improved by the same slow and gradual

process, they will spread more widely, and will be recognised as

something distinct and valuable, and will then probably first receive a

provincial name. In semi-civilised countries, with little free

communication, the spreading of a new sub-breed will be a slow process.

As soon as the points of value are once acknowledged, the principle, as

I have called it, of unconscious selection will always tend—perhaps

more at one period than at another, as the breed rises or falls in

fashion—perhaps more in one district than in another, according to the

state of civilisation of the inhabitants—slowly to add to the

characteristic features of the breed, whatever they may be. But the

chance will be infinitely small of any record having been preserved of

such slow, varying, and insensible changes.

_Circumstances favourable to Man’s Power of Selection._

I will now say a few words on the circumstances, favourable or the

reverse, to man’s power of selection. A high degree of variability is

obviously favourable, as freely giving the materials for selection to

work on; not that mere individual differences are not amply sufficient,

with extreme care, to allow of the accumulation of a large amount of

modification in almost any desired direction. But as variations

manifestly useful or pleasing to man appear only occasionally, the

chance of their appearance will be much increased by a large number of

individuals being kept. Hence number is of the highest importance for

success. On this principle Marshall formerly remarked, with respect to

the sheep of part of Yorkshire, “As they generally belong to poor

people, and are mostly _in small lots_, they never can be improved.” On

the other hand, nurserymen, from keeping large stocks of the same

plant, are generally far more successful than amateurs in raising new

and valuable varieties. A large number of individuals of an animal or

plant can be reared only where the conditions for its propagation are

favourable. When the individuals are scanty all will be allowed to

breed, whatever their quality may be, and this will effectually prevent

selection. But probably the most important element is that the animal

or plant should be so highly valued by man, that the closest attention

is paid to even the slightest deviations in its qualities or structure.

Unless such attention be paid nothing can be effected. I have seen it

gravely remarked, that it was most fortunate that the strawberry began

to vary just when gardeners began to attend to this plant. No doubt the

strawberry had always varied since it was cultivated, but the slight

varieties had been neglected. As soon, however, as gardeners picked out

individual plants with slightly larger, earlier, or better fruit, and

raised seedlings from them, and again picked out the best seedlings and

bred from them, then (with some aid by crossing distinct species) those

many admirable varieties of the strawberry were raised which have

appeared during the last half-century.

With animals, facility in preventing crosses is an important element in

the formation of new races—at least, in a country which is already

stocked with other races. In this respect enclosure of the land plays a

part. Wandering savages or the inhabitants of open plains rarely

possess more than one breed of the same species. Pigeons can be mated

for life, and this is a great convenience to the fancier, for thus many

races may be improved and kept true, though mingled in the same aviary;

and this circumstance must have largely favoured the formation of new

breeds. Pigeons, I may add, can be propagated in great numbers and at a

very quick rate, and inferior birds may be freely rejected, as when

killed they serve for food. On the other hand, cats, from their

nocturnal rambling habits, can not be easily matched, and, although so

much valued by women and children, we rarely see a distinct breed long

kept up; such breeds as we do sometimes see are almost always imported

from some other country. Although I do not doubt that some domestic

animals vary less than others, yet the rarity or absence of distinct

breeds of the cat, the donkey, peacock, goose, &c., may be attributed

in main part to selection not having been brought into play: in cats,

from the difficulty in pairing them; in donkeys, from only a few being

kept by poor people, and little attention paid to their breeding; for

recently in certain parts of Spain and of the United States this animal

has been surprisingly modified and improved by careful selection; in

peacocks, from not being very easily reared and a large stock not kept;

in geese, from being valuable only for two purposes, food and feathers,

and more especially from no pleasure having been felt in the display of

distinct breeds; but the goose, under the conditions to which it is

exposed when domesticated, seems to have a singularly inflexible

organisation, though it has varied to a slight extent, as I have

elsewhere described.

Some authors have maintained that the amount of variation in our

domestic productions is soon reached, and can never afterward be

exceeded. It would be somewhat rash to assert that the limit has been

attained in any one case; for almost all our animals and plants have

been greatly improved in many ways within a recent period; and this

implies variation. It would be equally rash to assert that characters

now increased to their utmost limit, could not, after remaining fixed

for many centuries, again vary under new conditions of life. No doubt,

as Mr. Wallace has remarked with much truth, a limit will be at last

reached. For instance, there must be a limit to the fleetness of any

terrestrial animal, as this will be determined by the friction to be

overcome, the weight of the body to be carried, and the power of

contraction in the muscular fibres. But what concerns us is that the

domestic varieties of the same species differ from each other in almost

every character, which man has attended to and selected, more than do

the distinct species of the same genera. Isidore Geoffroy St. Hilaire

has proved this in regard to size, and so it is with colour, and

probably with the length of hair. With respect to fleetness, which

depends on many bodily characters, Eclipse was far fleeter, and a

dray-horse is comparably stronger, than any two natural species

belonging to the same genus. So with plants, the seeds of the different

varieties of the bean or maize probably differ more in size than do the

seeds of the distinct species in any one genus in the same two

families. The same remark holds good in regard to the fruit of the

several varieties of the plum, and still more strongly with the melon,

as well as in many other analogous cases.

To sum up on the origin of our domestic races of animals and plants.

Changed conditions of life are of the highest importance in causing

variability, both by acting directly on the organisation, and

indirectly by affecting the reproductive system. It is not probable

that variability is an inherent and necessary contingent, under all

circumstances. The greater or less force of inheritance and reversion

determine whether variations shall endure. Variability is governed by

many unknown laws, of which correlated growth is probably the most

important. Something, but how much we do not know, may be attributed to

the definite action of the conditions of life. Some, perhaps a great,

effect may be attributed to the increased use or disuse of parts. The

final result is thus rendered infinitely complex. In some cases the

intercrossing of aboriginally distinct species appears to have played

an important part in the origin of our breeds. When several breeds have

once been formed in any country, their occasional intercrossing, with

the aid of selection, has, no doubt, largely aided in the formation of

new sub-breeds; but the importance of crossing has been much

exaggerated, both in regard to animals and to those plants which are

propagated by seed. With plants which are temporarily propagated by

cuttings, buds, &c., the importance of crossing is immense; for the

cultivator may here disregard the extreme variability both of hybrids

and of mongrels, and the sterility of hybrids; but plants not

propagated by seed are of little importance to us, for their endurance

is only temporary. Over all these causes of change, the accumulative

action of selection, whether applied methodically and quickly, or

unconsciously and slowly, but more efficiently, seems to have been the

predominant power.