32 Life and Letters of Francis Galton 



Whatever we may think of Gal ton's arguments, it is clear that in 1886 

 he did not believe in the influence of natural selection as producing new 

 forms by acting on continuously varying small deviations. This may have 

 been due to the influence which the idea of perpetual regression * had upon his 

 mind. Whatever its source, Galton was in 1886 and later a firm believer, as 

 the above passage indicates, in evolution by mutation. He was a mutationist 

 before De Vries published his first paper on mutations (1900). 



(iii) On the Inheritance of Ability and its Application to the 

 Upper House of Legislature (pp. 497-9). 



Galton inquires how far the results for heredity in stattfre may be applied 

 to heredity in ability. He holds that considerable differences have to be 

 taken into account, and he classifies them under three heads : 



" Firstly, after making large allowances for the occasional glaring cases of inferiority on the 

 part of the wife to her eminent husband, I adhere to the view I expressed long since as the 

 result of much inquiry, historical and otherwise!, that able men select those women for their 

 wives who are not mediocre women, and still less inferior women, but those who are decidedly 

 above mediocrity. Therefore, so far as this point is concerned, the average regression in the son 

 of an able man would be less than one-third." 



On better data J than Galton had at his command the regression of son's 

 stature on father's stature is about "52 instead of - 33, and, allowing for 

 assertative mating, about *82 on the midparent instead of Galton's - 67. 

 When we introduce the grandparents the regression is not large. I think 

 these points will explain Galton's difficulty as to ability without resort to 

 the theory that extreme ability does not blend, which he suggests in his 

 second statement: 



"Secondly, very gifted men are usually of marked individuality, and consequently of a special 

 type. Whenever this type is a stable one, it does not blend easily, but is transmitted almost 

 unchanged, so that specimens of very distinct intellectual heredity frequently occur." 



Unfortunately Galton gives no illustrations, and without statistical 

 evidence it is difficult to interpret his meaning. 



" Thirdly, there is the fact that men who leave their mark on the world are very often those 

 who, being gifted and full of nervous power, are at the same time haunted and driven by a domi- 

 nant idea, and are therefore within a measurable distance of insanity. This weakness will 

 probably betray itself occasionally in disadvantageous forms among their descendants. Some of 

 these will be eccentric, others feeble-minded, others nervous, and some may be downright 

 lunatics." 



The same point has been made frequently since Galton's day, but although 

 isolated cases can of course be cited, the statement demands statistical 

 demonstration. We require to know first whether the men "who leave their 



* The theory of multiple regression shows us that if an individual mates with his like, he 

 may regress on exceptional parents, but his offspring will not regress on him, nor further de- 

 scendants either. A breed may be established if we select only parents and grandparents; the 

 regression is thus of minor importance compared with the homogamy. 



t See Vol. ii, p. 105. J Biometrika, Vol. ii, p. 381. 



