CHAPTER IV. 



Natural Selection {continued)— The purely Accidental Causes of Death — Mai- 

 Environments — The Necessarily-Fatal Environment — The Not-Neces- 

 sarily-Fatal Environment — The Necessary Mai-Environment. 



The distinction I have drawn in the last two chapters between 

 instinct and reason is a very necessary one. There is no man- 

 ner of donbt that the one is a safer guide than the other, and it 

 is equally true that the moral nature in man offers a severe check 

 to the operation of natural selection. My object has been to 

 throw these two facts into bold relief. Having done so, it 

 is now necessary to study in greater detail the operation of 

 natural selection in man, and in this inquiry we must have an 

 eye chiefly to its pathological side. 



The fact that man has been many thousands of years upon the 

 earth, while the entire population thereof is only a little more 

 than 14,000 millions, shows us that the checks to increase must 

 have been enormous. If the world were peopled afresh from 

 two individuals, all checks to increase being removed, the present 

 population might be reached in a comparatively short period of 

 time. Now, it is at once manifest that in this vast destruction 

 of life in the past there must have been a survival of the fittest. 

 Wherefore, it is ci priori evident that the principle of natural 

 selection has played some considerable part in the evolution of 

 the human race — the evolution of man from the ape-like man. 



No doubt, in many cases, the survival has not been of the 

 fittest — to wit, when death has been due to sheer accident ; but 

 we may be quite sure that, on the whole, it has been the fittest 

 which have survived and given to posterity the largest number 

 of offspring. The checks to increase are, of course, far the 

 greatest among savage communities, whose population may not 

 increase during many centuries. In many civilized communi- 

 ties, on the other hand, the population is steadily increasing, 



