Charles Darwin.

The origin of species online

. (page 48 of 50)
Online LibraryCharles DarwinThe origin of species → online text (page 48 of 50)
Font size
QR-code for this ebook

assigning any distinction in the two cases. The day will come when this will
be given as a curious illustration of the blindness of preconceived opinion.
These authors seem no more startled at a miraculous act of creation than at
an ordinary birth. But do they really believe that at innumerable periods in
the earth's history certain elemental atoms have been commanded suddenly
to flash into living tissues ? Do they believe that at each supposed act of crea-
tion one individual or many were produced? Were all the infinitely numerous
kinds of animals and plants created as eggs or seed, or as full grown? and in
the case of mammals, were they created bearing the false marks of nourish-
ment from the mother's womb? Undoubtedly some of these same questions
cannot be answered by those who believe in the appearance or creation of
only a few forms of life, or of some one form alone. It has been maintained
by several authors that it is as easy to believe in the creation of a million be-
ings as of one; but Maupertuis' philosophical axiom of "least action" leads
the mind more willingly to admit the smaller number ; and certainly we ought


not to believe that innumerable beings within each great class have been
created with plain, but deceptive, marks of descent from a single parent.

As a record of a former state of things, I have retained in the foregoing
paragraphs, and elsewhere, several sentences which imply that naturalists
believe in the separate creation of each species; and I have been much cen-
sured for having thus expressed myself. But undoubtedly this was the general
belief when the first edition of the present work appeared. I formerly spoke
to very many naturalists on the subject of evolution, and never once met
with any sympathetic agreement. It is probable that some did then believe in
evolution, but they were either silent or expressed themselves so ambiguously
that it was not easy to understand their meaning. Now, things are wholly
changed, and almost every naturalist admits the great principle of evolution.
There are, however, some who still think that species have suddenly given
birth, through quite unexplained means, to new and totally different forms.
But, as I have attempted to show, weighty evidence can be opposed to the
admission of great and abrupt modifications. Under a scientific point of view,
and as leading to further investigation, but little advantage is gained by be-
lieving that new forms are suddenly developed in an inexplicable manner from
old and widely different forms, over the old belief in the creation of species
from the dust of the earth.

It may be asked how far I extend the doctrine of the modification of
species. The question is difficult to answer, because the more distinct the
forms are which we consider, by so much the arguments in favor of com-
munity of descent become fewer in number and less in force. But some argu-
ments of the greatest weight extend very far. All the members of whole
classes are connected together by a chain of affinities, and all can be classed
on the same principle, in groups subordinate to groups. Fossil remains some-
times tend to fill up very wide intervals between existing orders. .

Organs in a rudimentary condition plainly show that an early progenitor
had the organ in a fully developed condition, and this in some cases impHes
an enormous amount of modification in the descendants. Throughout whole
classes various structures are formed on the same pattern, and at a very early
age the embryos closely resemble each other. Therefore I cannot doubt that
the theory of descent with modification embraces all the members of the same
great class or kingdom. I believe that animals are descended from at most
only four or five progenitors, and plants from an equal or lesser number.

Analogy would lead me one step further, namely, to the belief that all ani-
mals and plants are descended from some one prototype. But analogy may be
a deceitful guide. Nevertheless all living things have much in common, in
their chemical composition, their cellular structure, their laws of growth, and
their liability to injurious influences. We see this even in so trifling a fact as
that the same poison often similarly affects plants and animals, or that the
poison secreted by the gall-fly produces monstrous growths on the wild rose |
or oak tree. With all organic beings, excepting perhaps some of the very J
lowest, sexual reproduction seems to be essentially similar. With all, as far as
is at present known, the germinal vesicle is the same; so that all organisms


start from a common origin. If we look even to the two main divisions —
namely, to the animal and vegetable kingdoms — certain low forms are so
far intermediate in character that naturalists have disputed to which king-
dom they should be referred. As Professor Asa Gray has remarked, "the
spores and other reproductive bodies of many of the lower algse may claim
to have first a characteristically animal, and then an unequivocally vegetable
existence." Therefore, on the principle of natural selection with divergence
of character, it does not seem incredible, that, from some such low and inter-
mediate form, both animals and plants may have been developed; and, if
we admit this, we must likewise admit that all the organic beings which have
ever lived on this earth may be descended from some one primordial form.
But this inference is chiefly grounded on analogy, and it is immaterial
whether or not it be accepted. No doubt it is possible, as Mr. G. H. Lewes
has urged, that at the first commencement of life many different forms were
evolved; but if so, we may conclude that only a very few have left modified
descendants. For, as I have recently remarked in regard to the members of
each great kingdom, such as the Vertebrata, Articulata, etc., we have distinct
evidence in their embryological, homologous, and rudimentary structures,
that within each kingdom all the members are descended from a single pro-

When the views advanced by me in this volume, and by Mr. Wallace, or
when analogous views on the origin of species, are generally admitted, we
can dimly foresee that there will be a considerable revolution in natural his-
tory. Systematists will be able to pursue their labors as at present; but they
will not be incessantly haunted by the shadowy doubt whether this or that
form be a irue species. This, I feel sure, and I speak after experience, will
be no slight relief. The endless disputes whether or not some fifty species of
British brambles are good species will cease. Systematists will have only to
decide (not that this will be easy) whether any form be sufficiently constant,
and distinct from other forms, to be capable of definition; and if definable,
whether the differences be sufficiently important to deserve a specific name.
This latter point will become a far more essential consideration than it is at
present; for differences, however slight, between any two forms, if not
blended by intermediate gradations, are looked at by most naturalists as suffi-
cient to raise both forms to the rank of species.

Hereafter, we shall be compelled to acknowledge that the only distinction
between species and well-marked varieties is, that the latter are known or
believed to be connected at the present day by intermediate gradations,
whereas species were formerly thus connected. Hence, without rejecting the
consideration of the present existence of intermediate gradations between any
two forms, we shall be led to weigh more carefully and to value higher the
actual amount of difference between them. It is quite possible that forms
now generally acknowledged to be merely varieties may hereafter be thought
worthy of specific names; and in this case scientific and common language
will come into accordance. In short, we shall have to treat species in the same
manner as those naturalists treat genera, who admit that genera are merely


artificial combinations made for convenience. This may not be a cheering
prospect; but we shall at least be freed from the vain search for the undis-
covered and undiscoverable essence of the term species.

The other and more general departments of natural history will rise greatly
in interest. The terms used by naturalists, of affinity, relationship, com-
munity of type, paternity, morphology, adaptive characters, rudimentary and
aborted organs, etc., will cease to be metaphorical, and will have a plain
signification. When we no longer look at an organic being as a savage looks
at a ship, as something wholly beyond his comprehension; when we regard
every production of nature as one which has had a long history; when we
contemplate every complex structure and instinct as the summing up of
many contrivances, each useful to the possessor, in the same way as any great
mechanical invention is the summing up of the labor, the experience, the
reason, and even the blunders of numerous workmen; when we thus view
each organic being, how far more interesting — I speak from experience — does
the study of natural history become !

A grand and almost untrodden field of inquiry will be opened, on the
causes and laws of variation, on correlation, on the effects of use and disuse,
on the direct action of external conditions, and so forth. The study of domes-
tic productions will rise immensely in value. A new variety raised by man
will be a more important and interesting subject for study than one more
species added to the infinitude of already recorded species. Our classifica-
tions will come to be, as far as they can be so made, genealogies ; and will then
truly give what may be called the plan of creation. The rules for classifying
will no doubt become simpler when we have a definite object in view. We
possess no pedigree or armorial bearings; and we have to discover and trace
the many diverging lines of descent in our natural genealogies, by characters
of any kind which have long been inherited. Rudimentary organs will speak
infallibly with respect to the nature of long-lost structures. Species and
groups of species which are called aberrant, and which may fancifully be
called living fossils, will aid us in forming a picture of the ancient forms of
life. Embryology will often reveal to us the structure, in some degree ob-
scured, of the prototypes of each great class.

When we can feel assured that all the individuals of the same species, and
all the closely allied species of most genera, have, within a not very remote
period, descended from one parent, and have migrated from some one birth-
place; and when we better know the many means of migration, then, by the
light which geology now throws, and will continue to throw, on former
changes of climate and of the level of the land, we shall surely be enabled to
trace in an admirable manner the former migrations of the inhabitants of the
whole world. Even at present, by comparing the differences between the in-
habitants of the sea on the opposite sides of a continent, and the nature of the
various inhabitants on that continent in relation to their apparent means of
immigration, some light can be thrown on ancient geography.

The noble science of geology loses glory from the extreme imperfection
of the record. The crust of the earth, with its embedded remains, must not


be looked at as a well-filled museum, but as a poor collection made at hazard
and at rare intervals. The accumulation of each great fossiliferous formation
will be recognized as having depended on an unusual occurrence of favor-
able circumstances, and the blank intervals between the successive stages as
having been of vast duration. But we shall be able to gauge with some
security the duration of these intervals by a comparison of the preceding
and succeeding organic forms. We must be cautious in attempting to correlate
as strictly contemporaneous two formations, which do not include many
identical species, by the general succession of the forms of life. As species
are produced and exterminated by slowly acting and still existing causes,
and not by miraculous acts of creation; and as the most important of all
causes of organic change is one which is almost independent of altered and
perhaps suddenly altered physical conditions, namely, the mutual relation
of organism to organism — the improvement of one organism entailing the
improvement or the extermination of others; it follows, that the amount of
organic change in the fossils of consecutive formations probably serves as a
fair measure of the relative, though not actual lapse of time. A number of
species, however, keeping in a body might remain for a long period un-
changed, w^hile within the same period, several of these species, by migrating
into new countries and coming into competition with foreign associates,
might become modified ; so that we mixst not overrate the accuracy of organic
change as a measure of time.

In the future I see open fields for far more important researches. Psy-
chology will be securely based on the foundation already well laid by Mr.
Herbert Spencer, that of the necessary acquirement of each mental power
and capacity by gradation. Much light will be thrown on the origin of man
and his history.

Authors of the highest eminence seem to be fully satisfied with the view
that each species has been independently created. To my mind it accords^
better with what we know of the laws impressed on matter by the Creator,
that the production and extinction of the past and present inhabitants of the
world should have been due to secondary causes, like those determining the
birth and death of the individual. When I view all beings not as special
creations, but as the lineal descendants of some few beings which lived long
before the first bed of the Cambrian system was deposited, they seem to me
to become ennobled. Judging from the past, we may safely infer that not one
living species will transmit its unaltered likeness to a distinct futurity. And of
the species now living, very few will transmit progeny of any kind to a far
distant futurity; for the manner in which all organic beings are grouped
shows that the greater number of species in each genus, and all the species in
many genera, have left no descendants, but have become utterly extinct. We
can so far take a prophetic glance into futurity as to foretell that it will be
the common and widely spread species, belonging to the larger and dominant
groups within each class, which will ultimately prevail and procreate new
and dominant species. As all the living forms of life are the lineal descendants
of those which lived long before the Cambrian epoch, we may feel certain


that the ordinary succession by generation has never once been broken, and
that no cataclysm has desolated the whole world. Hence, we may look with
some confidence to a secure future of great length. And as natural selection
works solely by and for the good of each being, all corporeal and mental
endowments will tend to progress toward perfection.

It is interesting to contemplate a tangled bank, clothed with many plants
of many kinds, with birds singing on the bushes, with various insects flitting
about, and with worms crawling through the damp earth, and to reflect that
these elaborately constructed forms, so different from each other, and de-
pendent upon each other in so complex a manner, have all been produced
by laws acting around us. These laws, taken in the largest sense, being
Growth with reproduction; Inheritance which is almost implied by reproduc-
tion; Variability from the indirect and direct action of the conditions of
life, and from use and disuse: a Ratio of Increase so high as to lead to a
Struggle for Life, and as a consequence to Natural Selection, entailing
Divergence of Character and the Extinction of less improved forms. Thus,
from the war of nature, from famine and death, the most exalted object
which we are capable of conceiving, namely, the production of the higher
animals, directly follows. There is grandeur in this view of life with its
several powers, having been originally breathed by the Creator into a few
forms or into one; and that, while this planet has gone circling on according
to the fixed law of gravity, from so simple a beginning endless forms most
beautiful and most wonderful have been, and are being evolved.




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 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 "Philosophic Zoologique,"
and subsequently, 18 15, in the Introduction to his "Hist. Nat. des Animaux
sans Vertebres." In these works he upholds 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 miracu-
lous 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 gradations 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

*AristotIe, 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 fanner's corn when threshed out of doors, applies the same argument to organ-
ization; 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 acci-
dent. And in like manner as to other parts in which there appears to exist an adapta-
tion 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 what-
soever things were not thus constituted, perished and still perish." We here see the
principle of natural selection shadowed forth, but how little Aristotle fully compre-
hended the principle, is shown by his remarks on the formation of the teeth.



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 like-
wise 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 spontane-
ously generated.*

Geoffroy Saint-Hilaire, as is stated in his "Life," written by his son, sus-
pected, as early as 1 795, 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 done un probleme a reserver entierement a
I'avenir, suppose meme que I'avenir doive avoir prise sur lui."

In 18 13 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 18 18. In this paper he distinctly recognizes 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 im-
munity 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 inability to sustain the attacks

*I have taken the date of the first publication of Lamarck from Isidore Geoffroy
Saint-Hilaire's ("Hist. Nat. Generale," tom. ii. p. 405, 1859) excellent history of
opinion on this subject. In this work a full account is given of BufTon'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. 509-510), published in 1794. According to Isid. Geoffroy there is no
doubt that Goethe was an extreme partisan of similar views, as shown in the introduc-
tion 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 i794~95'


of disease, but from their incapacity of contending with their more vigorous
neighbors. The color of this vigorous race I take for granted, from what
has been aheady 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's 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 "Amaryllidacese" (1837, PP- ^9? 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,

Online LibraryCharles DarwinThe origin of species → online text (page 48 of 50)