RECORD: Darwin, C. R.  [Abstract of species theory sent to Asa Gray]. CUL-DAR6.51 Transcribed by John van Wyhe. (Darwin Online, http://darwin-online.org.uk/)
REVISION HISTORY: Transcribed by John van Wyhe, corrections by Kees Rookmaaker 8.2009. RN1
NOTE: This is Darwin's draft of an abstract of his theory, later copied by an amanuensis, and sent to Asa Gray. (See Correspondence vol. 6, p. 445) The draft was later sent to Joseph Dalton Hooker in June 1858 for Darwin's contribution to the Darwin-Wallace papers read at the Linnean Society of London on 1 July 1858. Compare with the published version in Darwin 1858.
This abstract was transcribed and published with an important introduction and notes in Correspondence vol. 7, Appendix III.
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Reproduced with permission of the Syndics of Cambridge University Library and William Huxley Darwin.
(1) It is wonderful what the principle of Selection by Man,
can do that is the picking out of individuals with any desired quality, & breeding from them, & again picking out, can do. Even Breeders have been astonished at their own results. They can act on differences inappreciable to an uneducated eye. Selection has been methodically followed in Europe for only the last half century. But it has occasionally & even in some degree methodically been followed in the most ancient times. There must have been, also, a kind of unconscious selection from the most ancient times, namely in the preservation of the most useful individual animals (without any thought of their breeding offspring) most useful to each race of man in his particular circumstances. The "roguing", as nurserymen call the destroying of varieties, which depart from their type is a kind of selection. I am convinced that intentional & occasional selection has been the main agent in making our domestic races. But, however, this may be, its great power of modification has been indisputably shown in late times. Selection acts only by the accumulation of very slight or greater variations, caused by external conditions, or by the mere fact that in generation the child is not
absolutely similar to its parent. Man by this power of accumulating variations adapts living beings to his wants, — may be said to make the wool of one sheep good for carpet & another for cloth &c.
(2.) Now suppose there was a being, who did not judge by mere external appearance, but could study the whole internal organization— who never was capricious,—
& who selected not for his own good, but for that of the being on which he was acting— suppose he went on who should go on selecting for one end during millions of generations, who will say what he might not do effect! In nature we have some slight variation, occasionally in all parts: & I think it can be shown that changed conditions of existence is the great main cause of the child not exactly resembling its parents; & in nature geology shows us what changes have taken place & are taking place. In regard to the number of generations We have almost unlimited time: no one but a practical geologist can fully appreciate this: think of the Glacial period, during the whole of which shells the
same species of shells at least have existed: there must have been during this period, millions on millions of generations.
(3) I think it can be shown that there is such an unerring power at work on natural selection (the title of my Book), which selects exclusively for the good of each organic being. The elder Decandolle, W. Herbert, & Lyell have written strongly on the struggle for life; but even they have not written strongly enough. Reflect that every being (even the Elephant) breeds at such a rate, that in a few years, at most a few centuries or thousands of years the surface of the earth would hold
these the progeny of any one species. I have found it hard constantly to bear in mind that the increase of every single being species is checked during some part of its life, or during some shortly recurrent generation. Only a few of those annually born can live to propagate their kind. What a trifling difference must often determine which shall survive & which perish.—
[in left margin] the progeny of any one species wd cover the surface of the earth
(4) Now take the case of a country undergoing some change:
& not freely open to immigration this will tend to cause some of its inhabitants to vary slightly; not but what I believe most beings vary at all times enough for selection to act on. Its inhabitants would be exposed to new conditions; Some of its inhabitants will be exterminated, & the remainder will be exposed to the mutual action of a different set of inhabitants, ( —which I believe to be can be shown to be more important to the life of each being than mere climate change. Now Considering the infinitely various ways, beings have to obtain food by struggling with other beings, to escape danger at various times of life, to have their eggs or seeds disseminated &c &c, I cannot doubt that during millions of generations some slight in individuals of a species will be born with some slight variation profiting profitable to some part of its economy: such will have a better chance of surviving, propagating its variety this variation, which will be slowly increased by the accumulative action of natural selection; and the increasing by accumulation, & finally [illeg] variety thus formed will either coexisting with coexist with or more commonly will exterminate its parent form. An organic being like the woodpecker or missletoe may thus come to be adapted to a score of contingencies: natural selection, accumulating only those slight variations in all parts of its structure, which are in any way useful to it, during any part of its life.
(5) Multiform difficulties will occur to everyone on this theory. Most can, I think, be satisfactorily answered.— "Natura non facit saltum" answers some of the most obvious.— The slowness of the change & only a very few undergoing change at any one time answers others. The extreme imperfection of our geological records answers others. —
(6.) One other principle, which may be called the principle of divergence plays, I believe, an important part in the origin of species. The same spot will support more life if occupied by very diverse forms: we see this in the many generic forms in a square yard of turf
(I have counted 20 species belonging to 18 genera) — or in the plants & insects on any little uniform islet belonging almost to as many genera & families as to species.—We can understand this with the higher animals, whose habits we best understand. We know that it has been experimentally shown that a plot of land will yield a greater weight if cropped with several species of grasses than with 2 or 3 species. Now every single organic being, by propagating so rapidly, may be said
to be striving its utmost to increase in numbers. So it will be with the offspring of any species after it has broken into varieties or sub-species or true species. And it follows, I think, from the
same area foregoing facts, that the varying offspring of any one each species will try (only few will succeed) to seize on as many & as diverse places in the economy of nature, as possible. Each new variety or species, when formed will generally take the place of & so exterminate its less well-fitted parent. This, I believe, to be the origin of the classification or arrangement of all organic beings at all times. These always seem to branch & sub-branch like a tree from a common trunk; the flourishing twigs destroying the less vigorous,—the dead & lost branches rudely representing extinct forms.- genera & families.—
This sketch is most imperfect; but in so short a space I cannot make it better. Your imagination must fill up very wide blanks.— Without some reflexion it will appear all rubbish; perhaps it will appear so after reflexion.— C. Darwin
This was sent about 9 months ago, but I daresay I can get Date
Sketch sent to Dr Asa Gray
Sketch sent to Dr Asa Gray
This was sent to A. Gray
8 or 9 months ago
I think October 1857
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Citation: John van Wyhe, editor. 2002-. The Complete Work of Charles Darwin Online. (http://darwin-online.org.uk/)
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