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Letter 2706B

Spencer, Herbert to Darwin, C. R.

22 Feb 1860

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    CD has caused a great change in HS's views, in showing how a great proportion of adaptation should be explained by natural selection not direct adaptation to changing conditions. HS had remarked on the survival of the best individuals as a cause of improvement in man, but he "& every one" overlooked selection of spontaneous variation. Believes so many kinds of indirect evidence must add up to a conclusive demonstration of the doctrine.


22d Feby. 1860

You have wrought a considerable modificn in the views I

held— While having the same general conception of the relation of species genera, orders &c as gradually arising by differentiation & divergence like the branches of a tree & while regarding these cumulative modifications as wholly due to the influence of surrounding circumss. I was under the erroneous impression that the sole cause was adaptation to changing conditions of existence brought about by habit, using the phrase conditions of existence in its widest sense as including climate, food, & contact with other organisms (for general statement of this view see Essay pp. 41. 45.) But you have convinced me that throughout a great proportion of cases, direct adaptation does not explain the facts, but that they are explained only by adaptation through Natural Selection—

Many (&c) must have been struck with the fact that among all races of organisms the tendency was for the best individs. only to survive & that so the goodness of the race was preserved

I have in Essay on Population &c remarked this as a cause of improvement among mankind—

But I & every one overlooked the selection of ``spontaneous'' variations without which I think you have clearly shown that many of the phenomena are insoluble.

You have shown that the doctrine furnishes explanations to phenomena otherwise inexplicable. However the argument may as yet fall short of direct demonstration yet the indirect demonstn. is to me conclusive. I take it to be incredible that so many different kinds of evidence shd coincide in supporting a doctrine that was untrue—

    Footnotes Add

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    f1 2706b.f1
    The letter has not been found. The text has been transcribed from Charles Lyell's scientific journal; it is also printed in Wilson ed. 1970, pp. 353--4. The entry in Lyell's journal is headed: `Herbert Spencer to C. Darwin, 22d Feby.1860 | H. S.'s own doctrine of ``evolution'' put on so satisfactory a basis.'
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    f2 2706b.f2
    Spencer refers to his article `The development hypothesis', reprinted in Spencer 1858--63, 1: 389--95. For CD's opinion of Spencer's work, see letter to Herbert Spencer, 2 February [1860], and Correspondence vol. 7, letter to Herbert Spencer, 25 November [1858].
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    f3 2706b.f3
    [Spencer] 1852. A copy of this paper was apparently enclosed with the letter (see letter to Herbert Spencer, 23 [February 1860]).
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