54 THE ORIGIN OF SPECIES 



sp3iies of animals being perfectly fertile. Some authors 

 believe that long-continued domestication eliminates this 

 strong tendency to sterility in species. From the history 

 of the dog, and of some other domestic animals, this 

 conclusion is probably quite correct, if applied to spe- 

 cies closely related to each other. But to extend it so 

 far as to suppose that species, aboriginally as distinct as 

 carriers, tumblers, pouters, and fantails now are, should 

 yield offspring perfectly fertile inter se, would be rash 

 in the extreme. 



From these several reasons, namely — the improbability 

 of man having formerly made seven or eight supposed 

 species of pigeons to breed freely under domestication; 

 — these supposed species being quite unknown in a wild 

 state, and their not having become anywhere feral; — these 

 species presenting certain very abnormal characters, as 

 compared with all other Columbidae, though so like the 

 rock-pigeon in most respects; — the occasional reappearance 

 of the blue color and various black marks in all the 

 breeds, both when kept pure and when crossed; — and 

 lastly, the mongrel offspring being perfectly fertile; — from 

 these several reasons, taken together, we may safely con- 

 clude that all our domestic breeds are descended from 

 the rock-pigeon or Columba livia with its geographical 

 sub-species. 



In favor of this view, I may add, first, that the 

 wild C. livia has been found capable of domestication 

 in Europe and in India; and that it agrees in habits 

 and in a great number of points of structure with all 

 the domestic breeds. Secondly, that, although an En- 

 glish carrier or a short-faced tumbler differs immensely 

 in certain characters from the rock-pigeon, yet that, by 



