1870.] COUSIN MARRIAGES. 1 29 



C. Darwin to John Lubbock. 



Down, July 17, 1870. 



My dear Lubbock, — As I hear that the Census will be 

 brought before the House to-morrow, 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. As you are aware, I have made experiments 

 on the subject during several years ; and it is my clear con- 

 viction that there is now ample evidence of tJie existence of a 

 great physiological law, rendering an enquiry with reference to 

 mankind of much importance. In England and many parts of 

 Eicrope 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 sho?ild 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 ; and 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, and dumbness, blindness, &c, should be ascer- 

 tained ; and all such assertions could be easily tested by the 

 returns from a single census. 



Believe me, 



Yours very sincerely, 

 Charles Darwin. 



[When the Census Act was passing through the House of 

 Commons, Sir John Lubbock and Dr. Playfair attempted to 

 carry out this suggestion. The question came to a division, 

 which was lost, but not by many votes. 



VOL. III. K 



