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Darwin Correspondence Project

To John Lubbock   17 July 1870

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

July 17 1870

My dear Lubbock

As I hear that the Census will be brought before the House tomorrow, I write to say how much I hope that you will express your opinion on the desirability of queries in relation to consanguineous marriages being inserted.1 As you are aware, I have made experiments on the subject during several years; & it is my clear conviction that there is now ample evidence of the existence of a great physiological law, rendering an enquiry with reference to mankind of much importance. In England & many parts of Europe the marriages of cousins are objected to from their supposed injurious consequences; but this belief rests on no direct evidence. It is therefore manifestly desirable that the belief should either be proved false, or should be confirmed, so that in this latter case the marriages of cousins might be discouraged.

If the proper queries are inserted, the returns would show whether married cousins have in their households on the night of the census as many children, as have parents who are not related; & should the number prove fewer, we might safely infer either lessened fertility in the parents, or which is more probable, lessened vitality in the offspring.

It is moreover much to be wished that the truth of the often repeated assertion that consanguineous marriages lead to deafness & dumbness, blindness &c, should be ascertained;2 & all such assertions could be easily tested by the returns from a single census—

Believe me | yours very sincerely | Charles Darwin


For more on the attitudes to consanguineous marriage around this time, see Anderson 1986 and Kuper 2002. See also Child 1862 and Adam 1865.


Adam, William. 1865. Consanguinity in marriage. Fortnightly Review 2: 710–30, 3: 74–88.

Anderson, Nancy Fix. 1986. Cousin marriage in Victorian England. Journal of Family History 11: 285–301.

Child, Gilbert William. 1862. On marriages of consanguinity. British and Foreign Medico-chirurgical Review 29: 461–71.

Kuper, Adam. 2002. Incest, cousin marriage, and the origin of the human sciences in nineteenth-century England. Past and Present 174: 158–83.


CD would like questions on consanguineous marriages inserted in the Census to ascertain effects, if any, on fertility.

Letter details

Letter no.
Charles Robert Darwin
John Lubbock, 4th baronet and 1st Baron Avebury
Sent from
Source of text
DAR 261.7: 6
Physical description
LS 3pp & ADraft 1p

Please cite as

Darwin Correspondence Project, “Letter no. 7281,” accessed on 16 June 2024,

Also published in The Correspondence of Charles Darwin, vol. 18