CONSANGUINEOUS MARRIAGES 243 



In the light of what is known of the effects of inbreeding and 

 cross breeding in plants and animals it is obvious that we are not 

 in a position to draw conclusions a priori in regard to inbreeding 

 and cross breeding in man. In the absence of direct observations 

 on the effect of crossing of any two races of human beings, we 

 might expect as a probable result that, in regard to general vigor, 

 (i) the progeny would be superior to both parents, (2) that they 

 would be inferior to both, (3) that they would be superior to the 

 one and inferior to the other, or (4) that they would be on the 

 same general level as either one. We might predict with some 

 assurance what would be the probable outcome as to the inheri- 

 tance of eye color, hair color and some other characters whose 

 mode of transmission has been studied in other cases. But con- 

 cerning most of the qualities that render one race superior to 

 another we should be justified in making only very guarded 

 suppositions. 



The results of inbreeding and cross breeding in man present a 

 general similarity to those observed in plants and animals. They 

 may reasonably be interpreted according to the Mendelian 

 scheme, although this circumstance might not enable us to say 

 whether, in general, they are desirable or the reverse. In regard 

 to the effect of consanguineous marriages especially, there has 

 accumulated a large number of observations. It is an undoubted 

 fact that such matings have frequently been followed by the 

 appearance of undesirable characteristics in the offspring. But in 

 weighing the evidence on this point one has to guard against being 

 imduly impressed by facts which have been especially selected to 

 support a particular thesis. Numerous cases have been reported 

 in which various defects have been associated with consanguin- 

 eous matings. It would be possible, however, to amass many 

 instances of this kind even if consanguinity had nothing to do 

 with the production of defect. With this caveat in mind let us 

 consider this possible influence of consanguinity in bringing to 

 light certain hereditary traits. 



The role of consanguinity in bringing forth feeble-minded off- 

 spring has been discussed by many authors who have reported 



