136 THE PRINCIPLES OF HEREDITY 



so many aboriginal tribes for example, the Lowland Celts 

 and before them their predecessors in Great Britain exter- 

 mination by immigrant hordes. Evolution against malaria, 

 therefore, has been very considerable. Secondly, the illness 

 occasioned by the disease is of a very sudden and marked 

 character ; and, therefore, observers are easily able to con- 

 trast its effects on individuals of different races, and to 

 perceive how much more resistant are those races which 

 have had prolonged experience of it than those to which it 

 is strange. 



219. So considerable has evolution against malaria been in 

 various parts of the world that it is scarcely necessary to 

 bring forward evidence in proof of it. Nothing indeed can 

 be plainer than that different races of mankind differ vastly 

 in their powers of resisting the disease, and that those races 

 that have had extended and disastrous experience of it are 

 much more resistant than those who have had little or no 

 experience of it. Even people who, on doctrinal grounds, 

 strenuously repudiate the idea of evolution in general, must 

 admit that in this case evolution has certainly occurred ; for 

 if, as they usually believe, all the races of mankind had a 

 common origin, then in no other way is explicable the differ- 

 ence which now exists between one race and another, not 

 only as regards disease, but also as regards size, shape, colour 

 and so forth for example, between Englishmen and West 

 African Negroes. 



220. But while this evolution, when once attention is 

 drawn to it, becomes so manifest that it is unnecessary to 

 waste time in marshalling in proof of it facts that are 

 notorious, we shall nevertheless find it interesting to note 

 how exactly the degree of evolution undergone by any race 

 coincides with the virulence of the disease to which it has 

 been subjected. This fact is admirably brought out in the 

 following table : 



"In Ceylon there died of malaria fevers per 1,000 of the 

 population 



Negroes . . . . .1*1 



Natives of India .... 4'5 



Malays . . . . .67 



Natives of Ceylon , . . 7*0 



Europeans (English) .... 24'6 " l 



221. The above table is even more significant than it 



1 Hirsch, Geographical and Historical Pathology (New Sydenham 

 Society, 1883), vol. i., p. 245. 



