242 METHODS AND RESULTS OF ETHNOLOGY iv 



before they will admit the infertility of crosses 

 between two allied kinds of plants. They will 

 then, I think, be satisfied that the doctrine in 

 question rests upon a very unsafe foundation ; that 

 the facts adduced in its support are capable of 

 many other interpretations ; and, indeed, that from 

 the very nature of the case, demonstrative evidence 

 one way or the other is almost unattainable. 

 A priori, I should be disposed to expect a certain 

 amount of infertility between some of the extreme 

 modifications of mankind ; and still more between 

 the offsprings of their intermixture. A posteriori, 

 I cannot discover any satisfactory proof that such 

 infertility exists. 



From the facts of ethnology I now turn to 

 the theories and speculations of ethnologists, 

 which have been devised to explain these facts, 

 ' and to furnish satisfactory answers to the inquiry 

 what conditions have determined the existence 

 of the persistent modifications of mankind, 

 and have caused their distribution to be what 

 it is ? ' 



These speculations may be grouped under 

 three heads : firstly the Monogenist hypotheses ; 

 secondly, those of the Polygenists; and thirdly, 

 that which would result from a simple application 

 of Darwinian principles to mankind. 



According to the Monogenists, all mankind have 

 sprung from a single pair, whose multitudinous 

 progeny spread themselves over the world, such as 



