CHAPTER SIXTY 



DISEASE IN RELATION TO HUMAN EVOLUTION 



1. IT is well known that the rate of evolution in The slow 

 various groups of animals differs greatly. Thus the ofman ' 

 insects have changed much more rapidly than the Pro- 

 tozoa, the mammals more than the insects. Man being 



a highly specialized mammal, we might naturally expect 

 to find some evidence of evolution in the many thou- 

 sands of years of his existence. It is true that the 

 Neanderthal man, of extremely remote times, is so dis- 

 tinct that he is regarded as a separate species ; but his 

 successor, the Cro-Magnon man, still belonging to the 

 prehistoric period, was a being like ourselves. The 

 finely formed skull is in no way inferior to that of 

 modern races, - - is, in fact, superior to some of them. 

 Within historic times new races have arisen, like the 

 English, from the mingling of old ones ; but there has 

 been no apparent forward evolution in physical struc- 

 ture. The most we can say is that there has been a 

 shuffling of characters, and probably among civilized 

 nations a slight increase in average size, owing to better 

 nutrition. Man is a variable animal, and his funda- 

 mental constancy of type during such a long period may 

 well be used as an argument against the existence of any 

 inherent tendency to progressive modification. 



2. Is it a fact, then, that man has remained exactly Evolution in 

 what he was, except for the mingling of races ? Dr. to 

 Archdall Reid remarked some years ago that if we 



wished to determine the direction of modification, we 

 should look for the causes of death. In other words, 

 such modification as may occur is not due to inherent 

 tendencies to change, but to a selective agency acting 

 in the presence of heritable variations. Since individ- 



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