SOCIAL AND WORLD ASPECTS 223 



of characters thus results in a motley assortment of 

 types, with some primitive and some advanced 

 mental, moral, or physical qualities in place of the 

 original more or less blended condition in the first 

 generation of the cross. It is questionable even if 

 marriages between North and South European races 

 are always wholly desirable in their results ; although 

 history shows, on the other hand, that the inter- 

 mixture of more closely related races is beneficial 

 as supplying increased vigour and a greater range of 

 alternative characters, to increase the potentialities 

 of the population or for selection to play upon. 



Not only within the historical period (see, for 

 example, Haddon, 191 9), but also among the races 

 of Neolithic and Palaeolithic man there is evidence 

 of the frequent shifting of peoples in various parts of 

 the world. Sometimes the defeated race was driven 

 out or exterminated, but ver}- often such migrations 

 resulted in the fusion of two races into a new unit 

 ultimately having certain uniform and distinctive 

 features. It is evident that h^'bridisation has been 

 going on in this way at intervals throughout the 

 histor}- of man. It does not follow, as some writers 

 assume, that crossing is the cause of the evolution, 

 but it does follow that the great majority at least of 

 modern races are hybrid in origin, although they may 

 have become quite uniform through isolation and 

 inbreeding. The fact is that any racial unit contains 

 the potentialities of innumerable minor races if these 

 could be separated out and inbred. The range of 

 migration of a people is an important element in 

 determining how many distinct types will occupy a 

 given area of territor}'. When the Indian tribes of 

 the central plains of North America took to a nomadic 

 life after the introduction of the horse, many of the 

 tribal differences between them quickly disappeared. 

 Differences can only grow up in a condition of 



