GENETIC TYPE AND THE ENDOCEINES 29 



for man, nor so strong a tendency for a close association with 

 him. 



The second reason for the uncertainty regarding the wild 

 origin of the domestic dog breeds is that this did not involve 

 simply a single species of wild canine, but was probably more 

 complex, involving a number of species or kinds in various 

 regions of the world. The ancestry of the dog probably 

 reaches back to several stocks rather than to a single stem, 

 and since domestication took place so early in prehistoric 

 times, the lines of descent have long since become too hazy 

 for accurate tracing. 



Darwin, in his classical treatise on The Variation of Animals 

 and Plants under Domestication, epitomized in 1875 the 

 opinions of that time regarding the origin of the modern 

 dogs as follows : 



"Some authors believe that all have descended from the wolf 

 or from the jackal or from an unknown and extinct species. 

 Others again believe, and this of late has been the favourite 

 tenet, that they have descended from several species, extinct 

 and recent, more or less commingled together. We shall 

 probably never be able to ascertain their origin with cer- 

 tainty. Palaeontology does not throw much light on the 

 question, owing, on the one hand, to the close similarity of 

 the skulls of extinct as well as living wolves and jackals, 

 and owing, on the other hand, to the great dissimilarity of 

 the skulls of the several breeds of the domestic dogs. It 

 seems, however, that remains have been found in the later 

 tertiary deposits more like those of a large dog than of a 

 wolf, which favours the belief of DeBlainville that our dogs 

 are the descendants of a single extinct species. On the other 

 hand, some authors go so far as to assert that every chief 

 domestic breed must have had its wild prototype. This latter 

 view is extremely improbable : it allows nothing for variation ; 

 it passes over the almost monstrous character of some of 

 the breeds; and it almost necessarily assumes that a large 

 number of species have become extinct since man domesticated 

 the dog ..." (p. 15, v. 1.) 



Isidore Geoffroy Saint-Hilaire (Hist. Nat. Gen. 1860, T. 

 Ill, p. 107) stated his belief that most dogs descended from 

 the jackal although some may have descended from the wolf. 



