via THE DEVELOPMENT OF HUMAN RACES 175 



or totally fails, it can only exist by becoming adapted to a new 

 kind of food, a food perhaps less nourishing and less digestible. 

 Natural selection will now act upon the stomach and intes- 

 tines, and all their individual variations will be taken advan- 

 tage of, to modify the race into harmony with its new food. 

 In many cases, however, it is probable that this cannot be 

 done. The internal organs may not vary quick enough, and 

 then the animal will decrease in numbers and finally become 

 extinct. But man guards himself from such accidents by 

 superintending and guiding the operations of nature. He 

 plants the seed of his most agreeable food, and thus procures 

 a supply, independent of the accidents of varying seasons or 

 natural extinction. He domesticates animals, which serve him 

 either to capture food or for food itself, and thus changes of 

 any great extent in his teeth or digestive organs are rendered 

 unnecessary. Man, too, has everywhere the use of fire, and 

 by its means can render palatable a variety of animal and 

 vegetable substances, which he could hardly otherwise make 

 use of, and thus obtains for himself a supply of food far 

 more varied and abundant than that which any animal can 

 command. 



Thus man, by the mere capacity of clothing himself, and 

 making weapons and tools, has taken away from nature that 

 power of slowly but permanently changing the external form 

 and structure in accordance with changes in the external 

 world, which she exercises over all other animals. As the 

 competing races by which they are surrounded the climate, 

 the vegetation, or the animals which serve them for food are 

 slowly changing, they must undergo a corresponding change 

 in their structure, habits, and constitution to keep them in 

 harmony with the new conditions to enable them to live 

 and maintain their numbers. But man does this by means 

 of his intellect alone, the variations of which enable him, with 

 an unchanged body, still to keep in harmony with the changing 

 universe. 



There is one point, however, in which nature will still act 

 upon him as it does on animals, and, to some extent, modify 

 his external characters. Mr. Darwin has shown that the colour 

 of the skin is correlated with constitutional peculiarities both 

 in vegetables and animals, so that liability to certain diseases 



