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.
You have wrought a considerable modific
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 circums
Many (&c) must have been struck with the fact that among all races of organisms
the tendency was for the best individ
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
- f1 2706b.f1The 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, 22
dFeb y.1860 | H. S.'s own doctrine of ``evolution'' put on so satisfactory a basis.'
- f2 2706b.f2Spencer 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 , and Correspondence vol. 7, letter to Herbert Spencer, 25 November .
- f3 2706b.f3[Spencer] 1852. A copy of this paper was apparently enclosed with the letter (see letter to Herbert Spencer, 23 [February 1860]).