AN HISTORICAL SKETCH OF THE PROGRESS OF OPINION ON THE ORIGIN OFIRST EDITION OF THIS WORK
F 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,* 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 * Aristotle, in his
'Physicae 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 organization: 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 the 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. or means
of the transformation of species, I need not here enter on details.
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, in 1815, in the Introduction to his
"Hist. Nat. des Animaux sans Vertébres.' In these works he
upholds the doctrine that 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
seemed 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.*
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. *I have
taken the date of the first publication of Lamarck from Isid. Geoffroy
Saint-Hilaire's ('Hist. Nat. Générale,' tom. ii. p.
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. pp. 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 afterwards: he has
pointedly remarked ('Goethe als Naturforscher,' von Dr Karl Medinge 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 meme 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 resembled 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 the others to bear the diseases of the country. This race
would consequently multiply, while the others would decrease; not only from their inability 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 in Dr Wells' work.
The Hon. and Rev. W. Herbert, afterwards Dean of Manchester, in the
fourth volume of the 'Horticultural Transactions,, 1822, and in his
work on the 'Amaryllidaceae' (1837, pp. 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 intercrossing, 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. p. 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 55th 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 'Gardener's Chronicle,' on April
7th, 1860. The differences of Mr Matthew's view from mine are not of
much importance; he seems to consider that the world was
nearly depopulated at successive periods, and then re-stocked; and he
gives as an alternative, that new forms may be generated ' without the
presence of any mould 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, p. 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 (p. 6) as follows: -'All species might have been varieties once,
and many varieties are gradually becoming species by assuming constant
and peculiar characters'; but farther on (p. 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. p. 468) has ably given the arguments for and against
the hypothesis of the development and modification of species: he
seems to lean towards the side of change.
The "Vestiges of Creation' appeared in 1844. In the tenth and much
improved edition (1853) the anonymous author says (p. 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 co-adaptations 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 earlier
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 N. J. d'Omalius d'Halloy published in
an excellent though short paper ("Bulletins de l'Acad. Roy Bruxelles,'
tom. xiii. p. 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,' p. 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 (p. li.) of "the axiom of the continuous operation of
creative power, or of the ordained becoming of living things.' Farther
on (p. 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 zoologists 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 & 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 palaeontologists as being
firmly convinced of the immutability of species; but it appears
('Anat. of Vertebrates,' vol. iii. p. 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. p. 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. nl. p. 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. p. 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.
N. Isidore Geoffroy Saint-Hilaire, in his lectures delivered in
1850 (of which a Résumé appeared in the 'Revue et Nag.
de Zoolog.,' jan. 1851), briefly gives his reason for believing that
specific characters "sont fixés, pour chaque espèce,
tant quélle se perpétue au milieu des mèmes
circonstances: ils se modifient, si les circonstances ambiantes
viennent à changer.' 'En résumé, l'observation des animaux sauvages
démontre déjà la variabilité limité des espèces. Les expériences sur les animaux sauvages
devenus domestiques, et sur les animaux domestiques redevenus s auvages, la démontrent plus clairement
encore. Ces memes ex' - ces prouvent, de plus, que les
différences produites peuvent peuvent etre de valenr générique.' In his 'Hist.
Nat. Généralé (tom. ii.p. 430, 1859) he
amplifies analogous conclusions.
From a circular lately issued it appears that Dr Ereke, in 1851
("Dublin Medical press,' p. 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.
ln 1852 N. Naudin, a distinguished botanist, expressly stated, in
an admirable paper on the Origin of Species ('Revue Horticole, p. 1o2;
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 firiality, 'puissance
mystérieuse, indéterminée; fatalité pour
les uns; pour les autrese volonté providentielle, dont l'action
incessante sur les ètres vivants 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'ètre.'*
* From references in Bronn's 'Untersuchungen über die
Entwickenlungs-Gesetze,' it appears that the celebrated botanist and
palaeontologist Unger published, in 1852, his belief that species
undergo development and modification. Dalton, likewise, in pander and
Dalcon'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'Espéce,' it seems that Bory St Vincent, Burdach, Poiret,
and Fries, have all admitted that new
species are continually being produced. In 1853 a
celebrated geologist, Count Keyserling ("Bulletin de la Soc.
Gèolog.,' 2nd Ser., tom. x. p. 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.'
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 onspecial branches of natural history or geology.
A well-known French botanist, N. Lecoq, writes in 1854 ('Etudes sur
Géograph. Bot.,' tom. i. p. 250), 'On voit que nos recherches
sur la fixité ou la variation de l'espèce, nous
conduisent directement aux idées émises, par deux hommes
justement célèbres, Geoffroy Saint-Hilaire et Goethe.'
Some other passages scattered through N. 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 1st, 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, towards whom all zoologists feel so profound a respect,
expressed about the year 1859 (see prof. Rudolph Wagner, a "
Zoologisch-Anthropologische Untersuchugen,' 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 24th,
1859, and the second edition on January 7th, 1860.
WHEN on board H.M.S.
Beagle, as naturalist, I was much struck
with certain facts in the distribution of the inhabitants of South
America, and in the geological relations of the present to the past
inhabitants of that continent. These facts seemed to me 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 nearly finished; but as it will take me two or three
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. Last
year he sent to 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 will 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 cannot possibly be here done.
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 judgement.
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 each 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 most justly excites our admiration Naturalists
continually refer to external conditions, such as climate, food,
&c., as the only possible cause of variation. In one very 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 misseltoe, 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.
The author of the 'Vestiges of Creation' would, I presume, say
that, after a certain unknown number of generations, some bird had
given birth to a woodpecker, and some plant to the misseltoe, and that
these had been produced perfect as we now see them; but this
assumption seems to me to be no explanation, for it leaves the case of
the coadaptations of organic beings to each other and to their
physical conditions of life, untouched and unexplained.
It is, therefore, of the highest importance to gain a clear insight
into the means 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. or 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 his
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 amongst all organic beings
throughout the world, which inevitably follows from their high
geometrical powers of increase, will be treated of. 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 induces what I have called Divergence of
Character. In the next chapter I shall discuss the complex and little
Known laws of variation and of correlation of growth. In the four
succeeding chapters, the most apparent and gravest difficulties on the
theory will be given: namely, first, the difficulties of transitions,
or understanding how a simple being or a simple organ can be changed
and perfected into a highly developed being or 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 eleventh and twelfth, their geographical distribution
throughout space; in the thirteenth, 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 makes due
allowance for our profound ignorance in regard to the mutual relations
of all the 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 judgement of which I am capable,
that the view which most naturalists entertain, 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 main but not exclusive
means of modification.
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