During the voyage of the _Beagle_ I had been deeply imprest by
discovering in the Pampean formation great fossil animals, covered
with armor like that on the existing armadillos; secondly, by the
manner in which closely allied animals replace one another in
proceeding southward over the Continent; and thirdly, by the South
American character of most of the productions of the Galapagos
Archipelago, and more especially by the manner in which they differ
slightly on each island of the group; none of the islands appearing to
be very ancient in a geological sense.
[Footnote 18: From Darwin's "Autobiography," as printed in Volume 1 of
the "Life and Letters." Published by D. Appleton & Co.]
It was evident that such facts as these, as well as many others, could
only be explained on the supposition that species gradually become
modified; and the subject haunted me. But it was equally evident that
neither the action of the surrounding conditions, nor the will of the
organisms (especially in the case of plants), could account for the
innumerable cases in which organisms of every kind are beautifully
adapted to their habits of life; for instance, a woodpecker or a
tree-frog to climb trees, or a seed for dispersal by hooks or plumes.
I had always been much struck by such adaptations, and until these
could be explained it seemed to me almost useless to endeavor to
prove by indirect evidence that species have been modified.
After my return to England it appeared to me that by following the
example of Lyell in geology, and by collecting all facts which bore in
any way on the variation of animals and plants under domestication and
nature, some light might perhaps be thrown on the whole subject. My
first notebook was opened in July, 1837. I worked on true Baconian
principles; and without any theory collected facts on a wholesale
scale, more especially with respect to domesticated productions, by
printed inquiries, by conversation with skilful breeders and
gardeners, and by extensive reading. When I set the list of books of
all kinds which I read and abstracted, including whole series of
Journals and Transactions, I am surprized at my industry. I soon
perceived that selection was the keystone of man's success in making
useful races of animals and plants. But how selection could be applied
to organisms living in a state of nature, remained for some time a
mystery to me.
In October, 1838--that is, fifteen months after I had begun my
systematic inquiry--I happened to read for amusement "Malthus on
Population"; and being well prepared to appreciate the struggle for
existence which everywhere goes on from long-continued observation of
the habits of animals and plants, it at once struck me that under
these circumstances favorable variations would tend to be preserved,
and unfavorable ones to be destroyed. The result of this would be the
formation of new species. Here then I had at last got a theory by
which to work; but I was so anxious to avoid prejudice that I
determined not for some time to write even the briefest sketch of it.
In June, 1842, I first allowed myself the satisfaction of writing a
very brief abstract of my theory in pencil in thirty-five pages; and
this was enlarged during the summer of 1844 into one of two hundred
and thirty pages, which I had fairly copied out and still possess.
But at that time I overlooked one problem of great importance; and it
is astonishing to me, except on the principle of Columbus and his egg,
how I could have overlooked it and its solution. This problem is the
tendency in organic beings descended from the same stock to diverge in
character as they become modified. That they have diverged greatly is
obvious from the manner in which species of all kinds can be classed
under genera, genera under families, families under suborders, and so
forth: and I can remember the very spot in the road, while in my
carriage, when to my joy the solution occurred to me; and this was
long after I had come to Down. The solution, as I believe, is that the
modified offspring of all dominant and increasing forms tend to become
adapted to many and highly diversified places in the economy of
nature.
Early in 1856 Lyell advised me to write out my views pretty fully, and
I began at once to do so on a scale three or four times as extensive
as that which was afterward followed in my "Origin of Species"; yet it
was only an abstract of the materials which I had collected, and I got
through about half the work on this scale. But my plans were
overthrown, for early in the summer of 1858 Mr. Wallace, who was then
in the Malay Archipelago, sent me an essay "On the Tendency of
Varieties to Depart Indefinitely from the Original Type"; and this
essay contained exactly the same theory as mine. Mr. Wallace exprest
the wish that if I thought well of his essay, I should send it to
Lyell for perusal.
The circumstances under which I consented, at the request of Lyell and
Hooker, to allow of an abstract from my MS., together with a letter to
Asa Gray dated September 5th, 1857, to be published at the same time
with Wallace's essay, are given in the "Journal of the Proceedings of
the Linnean Society," 1858, page 45. I was at first very unwilling to
consent, as I thought Mr. Wallace might consider my doing so
unjustifiable, for I did not then know how generous and noble was his
disposition. The extract from my MS. and the letter to Asa Gray had
neither been intended for publication, and were badly written. Mr.
Wallace's essay, on the other hand, was admirably exprest and quite
clear. Nevertheless, our joint productions excited very little
attention, and the only published notice of them which I can remember
was by Professor Haughton of Dublin, whose verdict was that all that
was new in them was false, and what was true was old. This shows how
necessary it is that any new view should be explained at considerable
length in order to arouse public attention....
My habits are methodical, and this has been of not a little use for my
particular line of work. Lastly, I have had ample leisure from not
having to earn my own bread. Even ill health, tho it has annihilated
several years of my life, has saved me from the distractions of
society and amusement.
Therefore my success as a man of science, whatever this may have
amounted to, has been determined as far as I can judge by complex and
diversified mental qualities and conditions. Of these, the most
important have been the love of science, unbounded patience in long
reflecting over any subject, industry in observing and collecting
facts, and a fair share of invention as well as of common sense. With
such moderate abilities as I possess, it is truly surprizing that I
should have influenced to a considerable extent the belief of
scientific men on some important points.