560 HUMAN BIOLOGY 



that a species can maintain for a long time its specific 

 characteristics in the midst of such widespread mutation. 

 One answer to the last question is that so many mutations 

 are lethal, or disadvantageous, that their possessors are 

 eliminated. If all the traits that arise through mutation are 

 not disadvantageous they do not handicap the possessor 

 and may persist. If they give the possessor an advantage in 

 his environment or in some other environment to which he 

 may migrate then he will have a peculiar opportunity to 

 survive and perpetuate these advantageous qualities. An 

 important principle then is, to recapitulate, that each race 

 that has inhabited an environment for a long time has 

 become adjusted to that environment by the acquisition of 

 certain favorable mutations. 



The question at once arises, what happens in the case of 

 hybrids who are representatives of two such adjusted races? 

 Will the new combination of characters that arises in the 

 progeny be more or less fitting for the hybrids in the situation 

 in which they find themselves? 



With these general principles in view we proceed now to a 

 more or less systematic survey of the principal groups of 

 human hybrids that have been produced. 



I. Indian-European Crosses. A crossing between the 

 American Indian and the white man has frequently taken 

 place in the Americas. In South America the early Spanish 

 conquerors were young, single men, some of whom estab- 

 lished themselves in America and produced large families of 

 hybrids with the Indians. Some of the descendants of these 

 unions are among the leaders in South America. They have 

 more ambition than the average Indian and they are better 

 acclimated to the tropical conditions met with in certain 

 parts of the west coast of South America, than are the 

 Europeans. In the early days of North America also, French 

 adventurers penetrated in large numbers into Canada and 

 left a numerous hybrid progeny. These were often character- 

 ized by great vigor and activity and ability to withstand the 

 hardships of frontier life. Precise measurements of intelli- 

 gence of Indians, Mexicans and mixtures between them by 

 Garth (1922) leads to the conclusion that the mixed bloods 

 are the most intelligent of the groups. 



