SOCIAL AND WORLD ASPECTS 227 



hunting and fishing and general food-getting rights 

 over fixed hniited areas. Among the primitive races 

 of modern times these conditions continue. For 

 instance, in parts of former German South-West 

 Africa, where the chief Hottentot food-plant on parts 

 of the coast is a gourd, Acanthosicyos horrida, growing 

 on the sand-dunes, individual families and groups 

 have vested rights over the fruits of this plant in 

 local areas, and it annually saves their lives and 

 serves as a source of both food and water until other 

 food is obtainable. Native groups are, then, not free 

 to wander at will wherever fancy dictates, but each 

 party is confined to a limited area, whose boundaries 

 are definitely known to them. This fact, that each 

 group is definitely tied to a local area by recognised 

 custom and is often at war with its neighbours, adds 

 greatly to the stabilit}^ of any savage population, 

 and probably lessens the amount of exogamy between 

 unrelated families. These are the conditions under 

 which local tribes and differentiated groups might 

 be expected to grow up. Such a process of differentia- 

 tion is, however, ver}^ slow, and the spread of culture 

 from group to group will also tend to the maintenance 

 of uniformit}'. Nevertheless, cultural differences, 

 owing to local environmental conditions, will arise 

 long before structural differences appear, and in the 

 tribes of North American Indians such structural 

 differences seem to have been ver}^ few. Languages, 

 on the other hand, were many and often widely 

 different (though showing evidences of a common 

 origin), w^hich implied a long period of cultural 

 isolation. 



The results of crosses between such related tribes 

 are relativel}' insignificant, the differences involved 

 being less than those between the peoples of European 

 nations. Crosses between equally primitive or equally 

 advanced peoples of similar culture involve no very 



