INHERITED VARIATIONS AND FITNESS PROBLEMS 461 



THE TYPES OF SCAPULAE 



Among the types of inherited variations of structure, common to ancient 

 and modern man and other mammals (gorilla, orang, chimpanzee, armadillo, 

 bat, etc., etc.) are those of scapulae. Finding certain variations of scapular 

 vertebral borders in a family study in 1906, I was led to investigate scapu- 

 lar variations of man and other mammals, to classify them into types and 

 to apply the classification to family studies and to statistical studies of liv- 

 ing, skeletal and foetal human material. The classification is convex and 

 scaphoid (straight, concave and mixed) types, and it is based primarily upon 

 the character of the greater portion of the vertebral-border contour below 

 the scapular spine (figs. 1, 2 and 3). If the upper, middle or lower two- 

 thirds of this part of the bone be convex, straight or concave, it is so classi- 

 fied. With proper methods and with but few exceptions, scapular types are 

 easily accessible, readily recognizable and accurately classifiable in the liv- 

 ing. Scapular types are primal in origin. They are found in varying per- 

 centages in all social levels from the 12th foetal week onward in the life cycle. 

 Regardless of environmental influences and the processes of growth, develop- 

 ment and senescence, they remain permanent in type, and they are un- 

 usually constant in transmission from generation to generation: the scap- 

 hoid types, in man, as dominants. 



THE AGE INCIDENCE OF SCAPULAR TYPES: THEIR RELATION TO INHERITED 

 CAPACITIES FOR HEALTH, DISEASE AND DURATION OF LIFE 



The application of scapular classification to comparable numbers of the 

 young and the old disclosed the age incidence of scapular types — a hereto- 

 fore unknown finding in connection with inherited variations, whether of 

 structure or function. Scaphoid types predominate in the young, and convex 

 types predominate in the old in approximately the following percentages: 



Six to 15 years: 



per cent 



Scaphoid types 65 



Convex types 35 



Sixty years and over: 



Scaphoid types 35 



Convex types 65 



In all age periods in well-adaptable groups, there are more convex types and 

 fewer scaphoid types than in poorly-adaptable groups (table 2). 



