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Darwin Correspondence Project

To A. R. Wallace   5 May [1868]1

Down. | Bromley. | Kent. S.E.

May 5.

My dear Wallace

I am afraid I have caused you a great deal of trouble in writing to me at such length. I am glad to say that I agree almost entirely with your summary, except that I shd put sexual selection as an equal, or perhaps as even a more important, agent in giving colour than natural selection for protection.2 As I get on in my work I hope to get clearer & more decided ideas. Working up from the bottom of the scale I have as yet only got to fishes.3 What I rather object to in yr articles is that I do not think any one wd infer from them that you place sexual selection even as high as No 4 in yr summary:4 It was very natural that you shd give only a line to sexual selection in the summary to the West. Rev., but the result at first to my mind was that you attributed hardly any thing to its power.5 In your penultimate note you say “in the great mass of cases in which there is great differentiation of colour between the sexes, I believe it is due almost wholly to the need of protection to the female”.6 Now looking to the whole animal kingdom I can at present by no means admit this view; but pray do not suppose that because I differ to a certain extent, I do not thoroughly admire your several papers & yr admirable generalization on bird’s nests. With respect to this latter point, however, although following you, I suspect that I shall ultimately look at the whole case from a rather different point of view.7

You ask what I think about the gay-coloured females of Pieris; I believe I quite follow you in believing that the colours are wholly due to mimicry; & I further believe that the male is not brilliant from not having received thro’ inheritance colour from the female, & from not himself having varied; in short, that he has not been influenced by selection.8

I can make no answer with respect to the elephants. With respect to the female reindeer I have hitherto looked at the horns simply as the consequence of inheritance not having been limited by sex.9

Your idea about colour being concentrated in the smaller males seems good, & I presume that you will not object to my giving it as yr suggestion.10

Believe me my dear Wallace with many thanks | Yours very sincerely | Ch. Darwin


The year is established by the relationship between this letter and the letter from A. R. Wallace, 1 May [1868].
See letter from A. R. Wallace, 1 May [1868]. There are notes by CD relating to his debate with Wallace about coloration in birds, some dated 4 and 6 May 1868, in DAR 84.2: 4–8.
CD discussed secondary sexual characters in the ‘lower’ classes of the animal kingdom (‘such as the Protozoa, Coelenterata, Echinodermata, Scolecida’) in chapter 9 of Descent (Descent 1: 321–40), and fish in the first part of chapter 12 (Descent 2: 1–23). CD had been gathering information on sexual difference in fishes in late 1867 and early 1868; see Correspondence vol. 15, letter from A. C. L. G. Günther, [late December 1867 or early January 1868], and letters from Robert Buist, 26 February 1868 and 5 March 1868.
For Wallace’s summary, see the letter from A. R. Wallace, 1 May [1868].
Wallace wrote on the protective function of colour in insects and birds in Wallace 1867b (Westminster Review). In Wallace 1867b, Wallace wrote (pp. 41–2): It is the opinion of Mr. Darwin … that much of the development of colour in the animal world is due to ‘sexual selection,’ colour being universally attractive, and thus leading to its propagation and increase; but while fully admitting this, it will be evident, from the facts and arguments here brought forward, that very much of the variety both of colour and markings among animals, is due to the supreme importance of concealment.... We shall thus have two causes for the development of colour in the animal world, and shall be better enabled to understand how, by their combined and separate action, the immense variety we now behold has been produced.
CD discussed Wallace’s views on nesting habits and coloration in birds in Descent 2: 166–80.
See letter from A. R. Wallace, 1 May [1868]; see also Descent 1: 413–15 and n. 31.
See letter from A. R. Wallace, 1 May [1868]; CD discussed the tusks of female elephants and the horns of female reindeer in Descent 2: 243–4.
See letter from A. R. Wallace, 1 May [1868]. CD did not mention the greater intensity of colour in smaller males in Descent.


Criticism of ARW for too little esteem of the role of sexual selection as agent in giving colour.

Response to other topics.

Letter details

Letter no.
Charles Robert Darwin
Alfred Russel Wallace
Sent from
Source of text
British Library (Add 46434: 140–1)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 6161,” accessed on 24 June 2017,

Also published in The Correspondence of Charles Darwin, vol. 16