286 THE SCIENCE OF POWER 



with domestic birds. 1 But when once the Terror 

 had been transmitted to them through the social 

 heredity of their species they could not afterwards 

 be tamed. When brought up by a foster-parent the 

 young wild ducks acquired that exact relationship 

 of friendliness to man which the foster-parent dis- 

 played and which differed considerably according 

 to the birds used as foster-parents. 



I have found from observations in many countries 

 and on different animals that it is in the same way 

 that the exact distance up to which wild animals will 

 allow man to approach them is always imposed on 

 the young through social heredity. It represents the 

 accumulated experience of the species in the past. 

 The manner in which the inheritance is imposed on 

 the young in every generation may be watched even 

 in the streets of London in the case of the common 

 sparrow. When the young sparrows leave the ne t 

 they are comparatively tame. But they are 

 watched on the ground assiduously by the parents, 

 and when an enemy like man approaches to within a 

 certain distance, the cock parent utters a loud shrill 

 note expressing strong emotion which causes the 



1 Darwin, noting that " young chickens have lost that fear of 

 the dog and cat which no doubt was originally instinctive in 

 them," and perceiving the difficulty of explaining such a change 

 solely as due to selection, attributes it to an " inherited change 

 in mental habit" (Origin of Species, chap. viii.}. 



