SHORTER ARTICLES AND DISCUSSION 



THE CAUSE OF THE BELIEF IN USE INHERITANCE 



This note expresses an effort to view the old and recurring 

 problem of use inheritance from the aspect of the underlying 

 motives of thought involved instead of through a cunsiderat i<>n 

 of the evidence directly bearing upon it. 



The heredity of acquired traits is, theoretically, biological 

 heresy. But the interminable cropping out of the belief even in 

 professional circles indicates- a strong psychological impulse 

 toward the conviction. The mainspring of this impulse thus 

 becomes a matter of some importance to the student of heredity. 



To begin with, it is well known that the lay public almost with- 

 out exception takes use inheritance for granted. Even evolution, 

 in the real mental workings of most educated but unprofessional 

 people, is more generally explained, unconsciously and in con- 

 crete cases, by appeal to the machinery of use inheritance than to 

 that of selection. The phrases struggle for existence and sur- 

 vival of the fittest have indeed evoked a wide popular response on 

 account of their pi<-t uresqueiiess. but their concepts are still but 

 little employed, even in the intelligent and studied folk mind, as 

 a real means of understanding or explaining evolution. 



Those sporadic but in the aggregate numerous biologists who 

 adhere to the doctrine of use inheritance, revert to it, or evince 

 symptoms of a leaning toward it, may be divided into two types. 

 The first class, probably because they think more penetratingly 

 than the average, long ago perceived the inadequacy of selection 

 alone as an explanation of organic evolution; and more lately 

 perceive also the insufficiency of selection with mutations and 

 Mendelian phenomena superadded. To students of this type, use 

 inheritance is therefore merely a last resort, a hypothesis on 

 which they fall back in default of any other to stop a logical nap. 

 The only methodological criticism that can be made of this school 

 is that it would undoubtedly be more stimulating of new dis- 

 covery if we were frankly to avow the limits of our knowledge 

 and leave certain things unexplained, than to complete the mental 

 structure of evolution by piecing in a principle which admittedly 

 rests only on contested facts and has opposed to it about as large 

 a body of evidence as can be assembled on behalf of any negative 

 and therefore logically unprovable proposition. 



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