Human Variability 219 



who have short stubby fingers consisting of only two joints 

 (Fig. 56). 



These examples of deviations from the typical structure, 

 and of fluctuations in the normal form and proportions, are 

 taken for granted. They are sufficiently common in a large 

 population to pass without notice, and they remain well 

 within the limits of our common notion of the human race 

 or species. In respect to some of these qualities we assume 



Fig. 56. Brachydactyl Hands 



In some indiA'iduals the end segment of the fingers is missing, giving the fingers 

 a short, broad appearance. This condition has been traced through several gen- 

 erations, and seems to behave like a Mendelian dominant. After Farabee; 

 photograph through courtesy of the American Museum of Natural History. 



a direct relation to environment. To most people, for ex- 

 ample, stature appears to be related to nutrition, or to factors 

 such as disease or strain which may influence growth. Indeed 

 there is a considerable body of evidence to show that large 

 sections of the population living under unfavorable condi- 

 tions tend to be shorter on the whole than the more favorably 

 situated portions of the population. Moreover, there is con- 

 siderable recent evidence to show that children in America 

 tend to become taller than their parents were at correspond- 



