16 ON THE ORIGIN OF SPECIES 



terrier, spaniel, and bull-dog, which we all know pro- 

 pagate their kind so truly, were the offspring of any 

 single species, then such facts would have great weight 

 in making us doubt about the immutability of the 

 many very closely-allied natural species — for instance, 

 of the many foxes — inhabiting different quarters of the 

 world. I do not believe, as we shall presently see, that 

 the whole amount of difference between the several 

 breeds of the dog has been produced under domestica- 

 tion ; I believe that some small part of the difference is 

 due to their being descended from distinct species. In 

 the case of some other domesticated species, there is 

 presumptive, or even strong evidence, that all the 

 breeds have descended from a single wild stock. 



It has often been assumed that man has chosen for 

 domestication animals and plants having an extra- 

 ordinary inherent tendency to vary, and likewise to 

 withstand diverse climates. I do not dispute that these 

 capacities have added largely to the value of most of 

 our domesticated productions ; but how could a savage 

 possibly know, when he first tamed an animal, whether 

 it would vary in succeeding generations, and whether 

 it would endure other climates ? Has the little varia- 

 bility of the ass or guinea-fowl, or the small power 

 of endurance of warmth by the reindeer, or of cold by 

 the common camel, prevented their domestication ? 

 I cannot doubt that if other animals and plants, equal 

 in number to our domesticated productions, and 

 belonging to equally diverse classes and countries, 

 were taken from a state of nature, and could be made 

 to breed for an equal number of generations under 

 domestication, they would vary on an average as largely 

 as the parent species of our existing domesticated pro- 

 ductions have varied. 



In the case of most of our anciently domesticated 

 animals and plants, I do not think it is possible to 

 come to any definite conclusion, whether they have 

 descended from one or several wild species. The 

 argument mainly relied on by those who believe in the 

 multiple origin of our domestic animals is, that we 



