vin THE DEVELOPMENT OF HUMAN RACES 171 



secure its prey, to escape from its enemies, to resist the 

 inclemencies of the seasons, and to rear a numerous and 

 healthy offspring. But a change now takes place. A series 

 of cold winters, for instance, come on, making food scarce, 

 and bringing an immigration of some other animals to com- 

 pete with the former inhabitants of the district. The new 

 immigrant is swift of foot, and surpasses its rivals in the 

 pursuit of game ; the winter nights are colder, and require a 

 thicker fur as a protection, and more nourishing food to keep 

 up the heat of the system. Our supposed perfect animal is 

 no longer in harmony with its universe ; it is in danger of 

 dying of cold or of starvation. But the animal varies in its 

 offspring. Some of these are swifter than others they still 

 manage to catch food enough ; some are hardier and more 

 thickly furred they manage in the cold nights to keep warm 

 enough ; the slow, the weak, and the thinly clad soon die 

 off. Again and again, in each succeeding generation, the 

 same thing takes place. By this natural process, which is so 

 inevitable that it cannot be conceived not to act, those best 

 adapted to live, live ; those least adapted, die. It is some- 

 times said that we have no direct evidence of the action of 

 this selecting power in nature. But it seems to me we have 

 better evidence than even direct observation would be, 

 because it is more universal, viz., the evidence of necessity. 

 It must be so ; for, as all wild animals increase in a geomet- 

 rical ratio, while their actual numbers remain on the 

 average stationary, it follows that as many die annually as 

 are born. If, therefore, we deny natural selection, it can 

 only be by asserting that, in such a case as I have supposed, 

 the strong, the healthy, the swift, the well clad, the well 

 organised animals in every respect, have no advantage over 

 do not on the average live longer than the weak, the 

 unhealthy, the slow, the ill-clad, and the imperfectly organised 

 individuals ; and this no sane man has yet been found hardy 

 enough to assert. But this is not all ; for the offspring on 

 the average resemble their parents, and the selected portion 

 of each succeeding generation will therefore be stronger, 

 swifter, and more thickly furred than the last ; and if this 

 process goes on for thousands of generations, our animal will 

 have again become thoroughly in harmony with the new con- 



