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Darwin Correspondence Project

To superintendent of a lunatic asylum1   20 January 1874

Down, | Beckenham, Kent.

Jan 20. 74

Dear Sir

My Son George Darwin (who is a good Mathematician, having been 2nd. Wrangler at Cambridge)2 has been at work for nearly a year in trying, by several independent statistical methods, to discover what proportion of all marriages are between first cousins; & he now feels pretty confident that his results will not be subject to an error of as much as one per cent. He is being greatly aided in this part of his inquiry by Dr. Farre the Registrar General.3

He now wishes to utilize his results by the discovery of the proportion of the offspring of 1st. cousin marrriages amongst the insane, idiotic, deaf & dumb &c.

I have for 30 years considered an answer to this inquiry of great importance. We have here I think, the rare case of an inquiry, the answer to wh. will be of value whatever it may be; for we shall either find that such marriages are injurious, or that we may persevere in them with impunity

Dr Maudsley has informed me that he thinks it very likely that you will consider the investigation of sufficient importance to be willing to help my son by asking the patients in the large asylum under your charge (thro’ your assistants), whether or or not they are the offspring of first cousins, & recording the answers in each case.4 The question which my son proposes shd. be asked is simply,—

‘Were your father & mother first cousins or not?’

The questioner will doubtless be the best judge of the most prudent way of approaching the subject & of explaining the question in each individual case & will be able to judge of the trustworthiness of the answer from the known character of each patient.

If you shd. be willing to undertake this laborious task, you wd. be conferring a great favour both on my son & myself; & I beg you will send the tabulated results to my son at Trinity College Cambridge, where he is a resident fellow.

I hope you will pardon the liberty I take in thus addressing you on this subject.—

I beg leave to remain | Dear Sir | Yours faithfully | Charles Darwin

P.S It wd. give my son also a further body of statistics on wh. to base his conclusions, if in the cases of 1st. cousin marriage, (i) the surname of the father & maiden-surname of the mother were tabulated (for these will probably be learnt by the questioner), & (ii) further if any cases were recorded where the father & mother of a patient, not the offspring of a 1st. cousin marriage, bore the same surname.

I wd. not think of asking you to make this further inquiry, if you think the answer to the main point (to wh. this is entirely independent) would be thereby rendered less trustworthy, or if it wd. at all seriously increase the labour of the investigation


The correspondent has not been identified; however, in his letter to James Crichton-Browne, 5 January 1874, CD mentioned several asylum directors whom he intended to contact for information about cousin marriage.
George was second in the final examination for the mathematical tripos at Cambridge in 1868; the position was known as ‘second wrangler’ (Cambridge University calendar 1868).
William Farr had corresponded with CD about cousin marriage in 1868 and had supported CD’s attempt to have questions on cousin marriage added to the 1871 census (see Correspondence vol. 16, letter from William Farr, 21 May 1868, and Correspondence vol. 18). In his later article on cousin marriage (G. H. Darwin 1875a, p. 163), George acknowledged Farr’s assistance in facilitating his research.
In his letter to James Crichton-Browne, 5 January 1874, CD said that he planned to meet with Henry Maudsley to obtain further suggestions on which asylum directors to contact. In G. H. Darwin 1875a, p. 166, George listed the doctors who had sent replies to his questions.


Cambridge University calendar: The Cambridge University calendar. Cambridge: W. Page [and others]. 1796–1950.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.


Would like recipient to ask inmates whether they are offspring of cousin marriages.

Letter details

Letter no.
Charles Robert Darwin
Superintendent of a lunatic asylum
Source of text
Bernard Quaritch (dealers) (2003)

Please cite as

Darwin Correspondence Project, “Letter no. 9251F,” accessed on 27 September 2021,

Also published in The Correspondence of Charles Darwin, vol. 22