346 AN INTRODUCTION TO MODERN GENETICS 



Italians in their own countries. His data also show differences between 

 groups belonging to the same "race" but having different nationality, but 

 in addition to this there were differences between groups of different 

 "race" within the same nation. There w^as also a very significant fact 

 that all city-dw^elling groups, independent of nation or race, scored 

 alike and higher than all the rural groups. 



4. Race Crossing 



It is often claimed that the crossing of widely different races of man 

 inevitably leads to undesirable biological results. On the other hand, 

 there is no doubt that most national groups have arisen through a 

 fusion between at least fairly different peoples, and in some cases the 

 hybridization may have been fairly wide; for instance, the Japanese 

 are probably a mixture of MongoUan and Malay stocks. 



The main disadvantage of crossing which would be suggested by 

 biological theory is that it would lead to the production of a dishar- 

 monious assemblage of characters. If there are gross anatomical, 

 physiological, or mental differences between the parents, the children 

 may develop an assortment of characters which do not fit well together. 

 Davenport^ has drawn particular attention to this possibiUty and has 

 stated that it is often found for anatomical characteristics, for instance, 

 in white Bushman crosses. But it will occur the more often the fewer 

 the genes on which the differences depend; if the parent genotypes 

 differ in multiple genes, we should expect something more Uke blend- 

 ing inheritance, and this is also found. It is impossible to say a priori 

 whether two races differ in many or only a few genes; we have already 

 mentioned that the colour differences between whites and South 

 Africans are due to a few genes, those between whites and West Africans 

 to many. Only painstaking investigations of particular crosses, such as 

 those made by Gates^ and Lotsy,^ can solve the question for each 

 individual case. 



It is extremely difficult to determine whether disharmonious men- 

 talities are produced by crossing, as is often alleged. In some cases, 

 e.g. in South America, crossbreds are not at all inferior in mentality to 

 the pure races, while recently Germany has discovered, perhaps with 

 some dismay, how many of her most famous sons have some Jewish 

 genes in their chromosomes. But such equahty or even superiority is 

 only found when there is no social handicap in being a crossbred. In 

 only too many parts of the world the social disadvantage of being a 



^ Davenport 1917. ^ Gates 1929. ' Lotsy 1928. 



