HUMAN EVOLUTION 225 



then is the only stringently selective agent amongst civilized 

 men. The types it weeds out are those that are weak against disease, 

 the survivors are those that are resistant to disease : it follows that 

 the only racial progression, certainly the only considerable racial 

 progression, that civilized human races undergo is one against 

 disease. 



371. This conclusion is likely to be controverted, and by none 

 more strenuously than by students of evolution, most of whom have 

 devoted attention exclusively to such peculiarities of shape, colour, 

 size, and the like, as mark obvious differences between species and 

 varieties, and who have not taken into account the actual causes 

 which eliminate human beings under conditions of civilization. 

 But, either heredity is of the same nature in man as in other species, 

 or it is not If it is not, how shall we account for the miracle of 

 adaptation, and for the constant retrogression of useless parts ? 

 Man, while supplying indubitable evidence of progression when 

 under selection, affords no clear instance of real progression in 

 the lack of it. If retrogression constantly accompanies cessation 

 or diminishing stringency of selection, it follows that only selec- 

 tion, which is sufficiently stringent, can be a cause of progression. 

 Amongst civilized men, then, what are the causes of stringent 

 selection other than disease ? What types of men are being 

 eliminated? In what direction precisely is progression occurring? 

 I have known men who have attempted to answer these questions, 

 but I have never known one who succeeded. At best they have 

 merely guessed vaguely at lines of elimination the existence of 

 which they were unable to demonstrate, or indicated lines of progres- 

 sion which they could not show were other than acquirements 

 due to the better development (through improved conditions) of 

 the descendants as compared with the ancestors. 



372. The reader has only to refer to his own experience of life 

 to perceive that not a single character save power of resisting 

 disease is stringently selected. Except in extreme cases such traits 

 as, for example, shortness of stature, muscular weakness, or lack 

 of beauty or intellect, are not serious bars to offspring. But great 

 susceptibility to disease is an absolute bar, for the individual 

 perishes in early life. Relative susceptibility is a lesser obstacle, 

 but individuals characterized by it are seriously handicapped, 

 and 22 1 1 of alcoholism. Of the total number of deaths 280,302 were of people 

 under 45 years of age, and 239,729 of older people; 18,871 infants died because 

 prematurely born, 2343 of teething, and 12,933 of convulsions. Doubtless in 

 the last three categories, disease, parental (through causing injury in utero) or filial, 

 was a potent factor. 



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