22 ON THE ORIGIN OF SPECIES 



crossing of any lesser number : how, for instance, could 

 a pouter be produced by crossing two breeds unless one 

 of the parent-stocks possessed the characteristic enor- 

 mous crop? The supposed aboriginal stocks must 

 all have been rock-pigeons, that is, not breeding or 

 willingly perching on trees. But besides C. livia, with 

 its geographical sub-species, only two or three other 

 species of rock-pigeons are known ; and these have not 

 any of the characters of the domestic breeds. Hence 

 the supposed aboriginal stocks must either still exist in 

 the countries where they were originally domesticated, 

 and yet be unknown to ornithologists ; and this, con- 

 sidering their size, habits, and remarkable characters, 

 seems very improbable ; or they must have become 

 extinct in the wild state. But birds breeding on preci- 

 pices, and good fliers, are unlikely to be exterminated; 

 and the common rock-pigeon, which has the same 

 habits with the domestic breeds, has not been exter- 

 minated even on several of the smaller British islets, 

 or on the shores of the Mediterranean. Hence the 

 supposed extermination of so many species having 

 similar habits with the rock-pigeon seems to me a very 

 rash assumption. Moreover, the several above-named 

 domesticated breeds have been transported to all parts 

 of the world, and, therefore, some of them must have 

 been carried back again into their native country ; but 

 not one has ever become wild or feral, though the 

 dovecot-pigeon, which is the rock-pigeon in a very 

 slightly altered state, has become feral in several places. 

 Again, all recent experience shows that it is most 

 difficult to get any wild animal to breed freely under 

 domestication ; yet on the hypothesis of the multiple 

 origin of our pigeons, it must be assumed that at least 

 seven or eight species were so thoroughly domesticated 

 in ancient times by half-civilised man, as to be quite 

 prolific under confinement. 



An argument, as it seems to me, of great weight, and 

 applicable in several other cases, is, that the above- 

 specified breeds, though agreeing generally in con- 

 stitution, habits, voice, colouring, and in most parts of 



