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Darwin Correspondence Project

Evolution

Darwin concluded On the origin of species with the words: 'There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling 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.'  This was his first use of the word 'evolution', in any form, in print.  He did not invent the term but with his mechanism of 'natural selection', supplemented by ideas about sexual selection, 'divergence' and inheritance, he did describe just how evolution - the continual development of new organisms - could take place. 

At last gleams of light have come, & I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable.
Darwin to Joseph Hooker, [11 January 1844]
If, as I believe that my theory is true & if it be accepted even by one competent judge, it will be a considerable step in science.
Darwin to Emma Darwin 5 July 1844
I have lately been especially attending to Geograph. Distrib, & most splendid sport it is,—a grand game of chess with the world for a Board.
Darwin to C. J. F. Bunbury, 21 April [1856]
The facts which kept me longest scientifically orthodox are those of adaptation … This difficulty, I believe I have surmounted.
Darwin to Asa Gray, 5 September [1857]
…if my explanation of these classes of facts be at all right, whole classes of organic beings must be included in one line of descent.
Darwin to Leonard Jenyns, 7 January [1860]
But if (& oh what a big if) we could conceive in some warm little pond … that a protein compound was chemically formed, ready to undergo still more complex changes…
Darwin to J. D. Hooker 1 February [1871]

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Cover sheet of Darwin's 1842 Pencil Sketch, in which he first uses the term 'Natural Selection'
http://cudl.lib.cam.ac.uk/view/MS-DAR-00006/5
Cover sheet of Darwin's 1842 Pencil Sketch, in which he first uses the term 'Natural Selection'
CUL DAR 6: 1
Cambridge University Library

Natural selection

How do new species arise?  This was the ancient question that Charles Darwin tackled soon after returning to England from the Beagle voyage in October 1836. Darwin realised a crucial (and cruel) fact: far more individuals of each species were born than could possibly survive.

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Letter from Darwin to Hooker discussing Origin
https://cudl.lib.cam.ac.uk/view/MS-DAR-00115-00078-A/8
Letter from Darwin to Hooker discussing Origin
CUL DAR 115: 78
Cambridge University Library

The "wicked book": Origin at 157

Origin is 157 years old.  (Probably) the most famous book in science was published on 24 November 1859.  To celebrate we have uploaded hundreds of new images of letters, bringing the total number you can look at here to over 9000 representing more than 2000 letters, written both before and after the book appeared.   You can now see examples of letters to Darwin from nearly 250 different people, and letters he wrote to 150 more.

…the wicked book which you have been so long a-hatching.

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A peacock
https://www.flickr.com/photos/33414049@N08/7339653286/
A peacock
Kristine Deppe

Sexual selection

Although natural selection could explain the differences between species, Darwin realised that (other than in the reproductive organs themselves) it could not explain the often marked differences between the males and females of the same species.  So what accounted for these 'secondary sexual characteristics'? The longer manes in male lions and beards in male humans? Antlers or horns being so much smaller, or completely absent, in some female deer or cattle?

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Varieties of pigeon
http://www.biodiversitylibrary.org/item/124753
Varieties of pigeon
Image from the Biodiversity Heritage Library. Digitised by Smithsonian Libraries

Inheritance

It was crucial to Darwin’s theories of species change that naturally occurring variations could be inherited.  But at the time when he wrote Origin, he had no explanation for how inheritance worked – it was just obvious that it did.  Darwin’s attempt to describe how heredity might work, his 'provisional hypothesis of Pangenesis’, was published in 1868 in his book, Variation of animals and plants under domestication

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Divergence figure from the Origin of Species
http://biodiversitylibrary.org/item/135954#page/138/mode/1up
Divergence figure from the Origin of Species
Image from the Biodiversity Heritage Library. Digitised by Harvard University Botany Libraries

Divergence

In a later account of how he had come to the evolutionary ideas published in Origin, Darwin wrote: 'Of all the minor points, the last which I appreciated was the importance & cause of the principle of Divergence' (to Ernst Haeckel, [after 10] August – 8 October [1864]).

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Alfred Russel Wallace
http://enriqueta.man.ac.uk/luna/servlet/s/6vu7ve
Alfred Russel Wallace
R8475
Copyright of The University of Manchester

Alfred Russel Wallace’s essay on varieties

The original manuscript about varieties that Wallace composed on the island of Gilolo and sent to Darwin from the neighbouring island of Ternate (Brooks 1984) has not been found. It was sent to Darwin as an enclosure in a letter (itself missing), and was subsequently sent by Darwin to Charles Lyell (letter to Charles Lyell, 18 [June 1858]). The only known version of the text is the one published in Journal of the Proceedings of the Linnean Society (Zoology) 3 (1859): 45–62, and this text is reprinted below.

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Darwin's draft outline of Species Theory, sent to Asa Gray in 1857
http://cudl.lib.cam.ac.uk/view/MS-DAR-00006/103
Darwin's draft outline of Species Theory, sent to Asa Gray in 1857
CUL DAR 6: 51-56
Cambridge University Library

Abstract of Darwin’s theory

There are two extant versions of the abstract of Darwin’s theory of natural selection. One was sent to Asa Gray on 5 September 1857, enclosed with a letter of the same date (see Correspondence vol. 6, letter to Asa Gray, 5 September [1857] and enclosure). It is in the hand of Ebenezer Norman, Darwin’s copyist and includes minor alterations and corrections by Darwin. The letter and enclosure are in Gray’s correspondence in the Gray Herbarium of Harvard University.

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Part of a letter from W. H. Miller to Darwin exploring the geometrical architecture of honey-combs
http://cudl.lib.cam.ac.uk/view/MS-DAR-00048/187
Part of a letter from W. H. Miller to Darwin exploring the geometrical architecture of honey-combs
CUL DAR 48: B1bbr
Cambridge University Library

The writing of "Origin"

From a quiet rural existence at Down in Kent, filled with steady work on his ‘big book’ on the transmutation of species, Darwin was jolted into action in 1858 by the arrival of an unexpected letter (no longer extant) from Alfred Russel Wallace outlining a remarkably similar mechanism for species change. This letter led to the first announcement of Darwin’s and Wallace’s respective theories of organic change at the Linnean Society of London in July 1858 and prompted the composition and publication, in November 1859, of Darwin’s major treatise On the origin of species by means of natural selection.

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