IV ALTERATIONS THROUGH DOMESTICATION 165 



species which have been domesticated have gra- 

 dually departed from the feral ancestral type, and 

 among the domestic descendants man has, by his 

 industry and through the use of methods which he 

 has discovered, established different types. It matters 

 little from our point of view whether the ancestral form 

 of our horse was one or many, for if many, they at all 

 events had doubtless one common ancestral form, and 

 we may consider all our present types and varieties of 

 any one species as having, in each case, one single an- 

 cestral form from which, as we see, they have con- 

 siderably and in manifold ways departed. Compare, 

 for instance, the Shetland pony, the racehorse, and 

 the heavy clrayhorsc of the north of France ; compare 

 the numerous and very different breeds of sheep, of 

 oxen, of hogs, of dogs, so useful in different ways. In 

 some cases the wild form has disappeared, and in 

 those where it yet exists we perceive to what extent 

 domestication has modified and transformed the de- 

 scendants of the original stock. Whatever may have 

 been the ancestor of our dogs, the differences the exist- 

 ing breeds exhibit are marked enough to illustrate our 

 thesis. 



The modifying influence of domestication makes 

 itself felt in all parts of the organism, even in its depths 

 and in its less external characters. For instance, if 

 we measure the skull-capacity of wild and domestic 



