62 Permanence and Evolution. 



fore been exterminated by man. We know 

 extremely little of the causes of the extinction 

 of any forms, but we can, I think, see that the 

 same qualities which may be summed up as a 

 certain unadventurous tameness of disposition 

 (as is shown by Galton),* which adapt an animal 

 for subjection to man, may also render its long 

 continuance in a wild state less likely. 



The common rock dove has not been exter- 

 minated even on small islands, but then it is 

 one of the wildest and boldest of birds, with 

 difficulty, (according to Brent, "Pigeon Book," 

 p. 14) made really tame. The other breeds 

 of pigeons are less wild, shy, and vigorous, 

 and besides had, in the Old World, the 

 rock dove to contend with in the struggle 

 for life. Being extinct they evidently must 

 have had some disadvantage to struggle against 

 in their native country ; it is, therefore, not to 

 be expected that their descendants would be- 



* Transactions of Ethnological Society, vol. iii. new series, p. 133. 



