6 A STUDY IN HEREDITY 



of animals has been slower ; nevertheless, many 

 breeders, within the short span of the working life, 

 have produced great changes in different species 

 and varieties. It will doubtless be objected that 

 man is different from Nature : that man selects with 

 care while Nature does not. But presently I shall 

 show that in all the races of mankind Nature is 

 selecting certain types of men for survival, for pro- 

 creation, with a stringency so extreme that, while no 

 race escapes decimation, some races are undergoing 

 extermination. 



For the purposes of this work it matters not 

 whether my readers subscribe to the doctrine of 

 evolution in its totality — whether they hold the 

 belief that all plants and animals had a common 

 origin. If they admit, as admit they must, that 

 races of plants and animals change somewhat under 

 altered surroundings, it is sufficient. We can then 

 start from a common basis, and have a hope that a 

 dispassionate consideration of evidence will lead us 

 to a common conclusion. All that can then be in 

 dispute between us is that which is still in dispute 

 to some extent among scientific men ; namely, the 

 method by which evolution works, the method by 

 which living species undergo change. 



