^^<^^^^^^»^^^^^<^^^^^^^^^^^^^^^«$^^^^^^^^^^^^^^$^»^^^$^ 



o 



Chapter lo 



Relation of Use and Disuse to Evolution 



NE of the things that everybody knows and, so far 

 as we can find out from the records, always has 

 known is this: Exercise increases power, whereas 

 the disuse of an organ or an ability leads to atrophy or to loss 

 of skill. We cannot promise anybody that through practice 

 he will surely attain perfection; but everybody knows that 

 only through practice is perfection ever attained. The gen- 

 eral fact is one of common observation, and is probably never 

 questioned. 



Now it stands to reason that those who improve them- 

 selves through the exercise of their powers will by so much, 

 be likely to have superior offspring. The inference is indeed 

 so patent that it is seldom questioned; and it has been a part 

 of accepted belief, for the most part tacit, for three thou- 

 sand years or more. Aristotle included this among his ob- 

 servations upon vital phenomena, and lent the weight of his 

 authority to the corollary that has come to be known as the 

 doctrine of prenatal influence, or " maternal impressions." 

 This also has an ancient and respectable tradition behind it, 

 being assumed by at least one of the Old Testament authors 

 — in connection with a certain transaction that attached an 

 economic advantage for one of the parties to an increased 

 number of striped or spotted sheep (Genesis xxx, xxxi) . 



One of Ezekiel's proverbs has been commonly inter- 

 preted not merely as an embodiment of this belief in the 

 transmission of modifications acquired through experience, 

 but as a biblical endorsement of the idea: " The fathers 

 have tasted of sour grapes, and the children's teeth are set 

 on edge." A similar interpretation is also sometimes made 



