i07o.] COUSIN MARRIAGES. 309 



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 de- 

 sirability 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 the existence of a great 

 physiological law, rendering an enquiry with reference to mankind 

 of much importance. In England and many parts of Europe the 

 marriages of cousins are objected to from their supposed injurious 

 consequences j 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 ; 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. 



