250 INBEEEDING AND OUTBEEEDING 



true, but they are presumably Mendelian. Consequently 

 one must be very cautious about drawing genetic conclu- 

 sions in the human race based upon the possession of 

 particular traits, in the absence of proof of a long-con- 

 tinued isolation. Long isolation, it must be assumed, 

 aided in segregating some well-marked human sub- 

 species. It may serv^e a purpose to continue to accept cer- 

 tain of these types as implied in the terms, white, yellow 

 and black races. Yet one must not forget that real isola- 

 tion belongs to past epochs. There has been no small 

 amount of interbreeding between even these main types, 

 and the magnitude of the interbreeding between sub-races 

 is largely a matter of historical record. Traits originally 

 characteristic of certain peoples because of isolation and 

 the consequent inbreeding have been shifted back and 

 forth, combined and recombined. It is positively mis- 

 leading, therefore, to classify Englishmen as resembliiig 

 Danish, Norman^ Pictic, Celtic or Bronze Age types, as is 

 done in more than one work of authority. Even if it were 

 known what the average values of the various characters 

 of these early strains were, there is little reason for be^ 

 lieving that a present-day individual bearing one or two 

 particularly striking traits should be felt to hold any 

 closer relationship to the strain in which these traits are 

 supposed to have arisen than his neighbors who are with- 

 out them. He may have outstanding characters which 

 were once peculiar to a comparatively pure race ; but he 

 probably carries these characters as a mere matter of 

 Mendelian recombination. It is wholly possible, for ex- 

 ample, that a tall, blue-eyed, dolichocephalic Frenchman 

 really possesses less of the so-called Nordic factors than a 

 short, dark-eyed round-head. 



