Ɛpsilon

To William Marshall   6 June [1872]1

Down, | Beckenham, Kent.

June 6th.

Dear Sir

Permit me to trouble you with a few lines to thank you for your kindness in having sent me various interesting publications; especially one on the structure of man in relation to the lower animals, & a second, received only a few days since, on the osseous protuberances of the skulls of Birds.2 I have been particularly glad to see this latter memoir, & have seldom been more interested than by your statement that these protuberances appear early in life in those species in which both sexes are thus furnished, & late in life in those in which the males alone possess them.3 This is a parallel case to that given by me in the Descent of Man about the horns of the Rein-Deer; & I believe that the fact has a very important bearing on the acquisition of sexual characters.4

It has pleased me much to observe that you admit to a considerable extent the influence of sexual selection.5

With much respect & my best thanks, I remain, Dear Sir | Yours faithfully | Ch. Darwin

1
The year is established by the relationship between this letter and the letter from William Marshall, 15 October 1872.
2
CD’s annotated copies of Marshall 1870 (on resemblances between humans and other animals) and 1872a (on bony protuberances on the skulls of birds) are in the Darwin Pamphlet Collection–CUL, together with papers sent by Marshall on elongated tail feathers in birds of paradise (Marshall 1871), and general observations on birds’ tails (Marshall 1872b).
3
See Marshall 1872a, p. 174; CD scored this passage three times in in his copy of the paper and wrote ‘very important’ in the margin.
4
CD had proposed in Descent that secondary sexual characteristics generally appeared later in life than characteristics that were shared by both sexes. He illustrated this with the case of reindeer, which develop antlers at an unusually early age and are the only members of the deer family in which females have antlers as well as males (Descent 1: 288, 295). CD added Marshall’s similar conclusions about birds to this section in Descent 2d ed., p. 235 and n. 43, citing Marshall 1872a; he also cited Marshall 1872a and 1872b in a discussion of the development of ornament, and Marshall 1871 on moulting in birds of paradise (Descent 2d ed., pp. 383–4 and nn. 65 and 66, 393 n. 82).
5
In his work on bony crests in birds, Marshall concluded that those found only in the males must often have arisen through sexual selection; he also suggested that some features that had arisen through sexual selection might not be easily identifiable as such, having assumed an additional function over time and lost their original role (Marshall 1872a, p. 174).

Manuscript Alterations and Comments

1.4 to see] interl

Please cite as “DCP-LETT-8371A,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-8371A