140 DARWINISM AND HUMAN LIFE 



in a domain where occurrences seem as capricious 

 as those of weather. 



It has often been remarked that the children 

 of extraordinarily gifted parents are sometimes 

 very ordinary individuals, and that the children 

 of under-average parents sometimes turn out 

 surprisingly well, both physically and mentally. 

 Every one who has looked into the facts of in- 

 heritance in greater detail, and has compared the 

 average of qualities in successive generations, 

 has noticed, in a general way, that there is a 

 tendency to sustain the same average level from 

 generation to generation. Even the older in- 

 quirers, like Lucas, called attention to the fact 

 that extraordinary qualities in families tend to 

 wane away, as if there were some mysterious 

 succession-tax levied on marked deviations from 

 the average, whether in the way of excellence or 

 of defect. But we owe to Galton's careful statisti- 

 cal work the generalisation known as the Law of 

 Filial Regression, which has replaced a vague 

 impression by a definite formula. He has defined 

 and measured the tendency towards mediocrity, 

 the tendency to approximate to the mean, or 

 average, of the stock. We must notice, at the 

 outset, that this Filial Regression has nothing to 

 do with reversion or with degeneration, that it 

 works upwards as well as downwards, forwards 

 as well as backwards. 



The data which Galton utilised were chiefly the 

 records of family faculties, obtained from about 

 one hundred and fifty families, and dealing especi- 

 ally with stature, eye-colour, temper, artistic 

 faculty, and some forms of disease. These were 

 supplemented by measurements at Galton 's anthro- 



