EVOLUTION 261 



We are certain that physical characters diagnostic of race and stock are 

 hereditary: they arose genetically, via mutations and subsequent isolation; 

 they have been perpetuated genetically in varying combinations. We 

 know, for example, that there is an average of "one mutation for every 

 50,000 individuals per generation" (Strandskov), and that most of these 

 mutations are of indifferent or even negative survival value. The few that 

 are positive are transmitted and over a long period of time have entered 

 into complexes and combinations which differ from stock to stock, and 

 within stocks from sub-type to sub-type, from variety to variety. We are 

 slowly but surely learning the genetics of Mankind in terms of his many 

 physical-type variants. 



A fourth "don't" is really a corollary of the third, namely, we realize 

 that discrete traits have a hereditary basis, but we are still not sure which 

 of these traits are relatively stable and which are easily modifiable, so 

 that the first set is useful in classification, the second extremely limited in 

 use. 



In studying problems of racial analysis Hooton ^ has outlined three cate- 

 gories of physical traits in Man: those that are non-adaptive, those that 

 possess an acquired stability, and those that are easily modified. We may 

 summarize these three categories as follows: 



There are certain features which appear to act as heritable entities, either 

 as unit characters or with multiple factors. These comprise in general 

 hair-color and eye-color, form of hair, eye-fold, nose, lips, ear, incisor 

 teeth and vertebral border of scapula, head breadth, face length, chin 

 prominence and prognathism, and limb proportions, including intra- 

 membral, inter-membral and trunk-limb ratios. These physical characters 

 are non-adaptive, stable, fixed, and may quite reasonably form the basis of 

 the assessment of racial distinctions. Furthermore, certain combinations of 

 these traits, varying within natural boundaries, result in the establishment 

 of subgroups within each major classification. 



We come now to several traits which have in the course of time been 

 functionally modified and by selection have become more or less stabilized; 

 at least their variability is of intra-racial rather than inter-racial magnitude. 

 Here we may include skin color, shape, size, and proportion of the molars 

 and the palatal arch, head height and brain volume, and possibly certain 

 calcaneo-gastrocnemic relationships. The list is small and its import un- 

 certain; the farther we go in our study of individual growth patterns and 

 their probable relation to presumed racial criteria the more we must allow 

 for modifiability. It may be that the stability is spurious, merely a transi- 

 tory phase in the creation of an ultimate pattern dictated by constitutional 

 vicissitudes. 



Finally, there are a number of bodily features so directly susceptible to 

 health, diet and food habits, climatic factors, gait, exercise, occupation 



^E. A. Hooton, "Methods of Racial Analysis," Science, 53: 75-81, 1926. 



