THE PRESENT EVOLUTION OF MAN — PHYSICAL 201 



ancestral lines will probably cease and retrogression 

 ensue ; unless, indeed, in a more enlightened era than 

 our own, the Natural Selection of man is replaced by 

 an Artificial Selection, which shall permit only the 

 happy in mind and body to perpetuate the race. 



But side by side with this evolution of brain and 

 body along ancestral lines, which has engrossed the 

 attention of biologists, but which now threatens to 

 cease, man, during the last few thousand years, during 

 which he has largely dwelt in towns and cities, has 

 been undergoing another and a vastly important evolu- 

 tion in a different direction, an evolution which has 

 escaped the observation of biologists, but which threatens 

 by the survival of the fittest and the elimination of the 

 unfittest to advance at accelerated speed in the near 

 future ; an evolution none the less real because it is 

 intangible. If we would discover in what direction the 

 evolution of an evolving species is proceeding, it is a 

 good plan to note which members of it survive and 

 which perish. We shall then, by observing the differ- 

 ence in qualities between the fit and the unfit, be able 

 to discover which traits favour survival, and therefore 

 which traits are undergoing evolution by the accumula- 

 tion of inborn variations. Applying this test to man, it 

 is manifest that the survivors in his species, they who 

 attain to maturity and have offspring, who continue the 

 race, are not, as in the remote past, necessarily the 

 strong in limb and mind, but necessarily the strong 

 against disease. The present evolution of man is there- 

 fore not mainly an evolution of physical or intellectual 

 strength, as in his remote ancestry, but mainly an 

 evolution against disease, and wherever men are 

 crowded together, and can take disease from one another, 

 or there are other unfavourable circumstances, especially 

 against • zymotic disease — that is, disease due to or 

 produced by living micro-organisms. 



