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Introduction
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.
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, etc., 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 admirable 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 condition 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. Nor have I been disappointed;
in this and in all other perplexing cases I have invariable 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.
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 judgment 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.
On the Origin of Species by Means of Natural Selection.
London. 1859.
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