MAN AND MANKIND 



conquered peoples. Hence the peripheral similarities of certain 

 sounds would seem to depend on their aboriginal origin. 



Thus the study of phonetic preference and its historical changes 

 and geographical distribution may provide us with a key for a new 

 and genetic approach to one of the simplest but most significant 

 aspects of the history of culture. 



Cliiics, Tribes and Classes 



Three ways of classifying man and defining his genetic variation 

 now become apparent. 



The first is clinal and depends on migrations and conquests 

 operating over great periods of time. These establish large-scale 

 gradients in genetic character which, in the Old World, show great 

 stability. The O blood-group gradient is an example. It runs across 

 Britain from north-west to south-east. A colour-vision defect 

 gradient on the other hand runs from north-east to south-west. 

 Hundreds of such gradients would be necessary to give even a 

 superficial description of the clinal variation of Europe, 



Superimposed on this primary type of human variation is another 

 working on an entirely different scale. Where mating groups have 

 been stabilized either by geographical or cultural barriers they 

 establish what we may call a tribal subdivision. This subdivision 

 must have a genetic importance proportionate to the duration of 

 stability and to the smallness of the group. For this reason the tribal 

 subdivision variegates the primary pattern of clinal variation to 

 different extents in different regions and periods. 



And finally, superimposed on the tribal subdivision, is the func- 

 tional one in respect of the classes and castes we have already 

 discussed. 



The relative importance of the three modes of variation in man will 

 depend on a number of circumstances. It will obviously depend on 

 the time and place under examination. During the Dark Ages in 

 Europe or after an Islamic conquest, clincs would have submerged 

 tribes just as they are doing with African tribes now. In the United 

 States and other new countries, on the contrary, owing to the freedom 

 of movement, classes and castes rather than tribes or clines are the 

 predominant mcrlunl of division. In Europe we find tliar subdivision 



364 



