510 THE CHANGING GENERATIONS 



evolution, and the factors that have molded his development. Further- 

 more race classification is useful in a purely descriptive way, since it 

 enables us to become familiar with the superficial characteristics of 

 more than 2 billion people in a reasonably short time. 



It should be obvious that there is another compelling reason for study- 

 ing and teaching about races. Knowledge is the only antidote for ignor- 

 ance and prejudice. The more about race people know, the less room there 

 will be for baseless antagonisms and unfounded notions of racial supe- 

 riority. And here let it be said that no tests yet devised have revealed any 

 inherent mental differences between the races of men. There are certainly 

 superior individuals in all races. There may also be superior cultures and 

 superior environments, but that is another matter. 



Genetics and the Races of Man. In 1950, Boyd published an impor- 

 tant book under the above title, in which he summarized our present 

 knowledge of human genetics as it bears upon race classification and the 

 genetic structure of human populations. As restated by Dobzhansky, 

 Boyd's thesis is as follows : Every human being is a member of a biological 

 community within which marriages take place. Such a community, 

 termed a Mendelian population or isolate, possesses a gene pool, from 

 which the genes of the individuals are drawn and to which some of them 

 are returned unless the individual dies childless. Mankind, the human 

 species, is the most inclusive Mendelian population. It is, however, a 

 very complex system of isolates, kept apart by geography or by social 

 forces. It happens that these subordinate populations often differ in the 

 relative frequencies of genes for various traits in their gene pools. Boyd 

 defines such different populations as races; his definition was quoted 

 above. He points out that which and how many groups of allelic genes 

 we choose to consider as differential criteria of race is an arbitrary matter. 



The way to describe races, then, should be to determine the frequencies 

 of particular allelic genes in human populations. However, only a few 

 traits are as yet sufficiently well understood genetically so that such 

 analysis can be made. The most important of these are the inherited 

 variations in some components of the blood — the blood groups. Because 

 of their medical importance and ease of determination certain blood 

 groups have been investigated in populations all over the world. Boyd's 

 analysis of the data is too complicated to be outlined here, but the follow- 

 ing will illustrate the method and its results. 



Of the various blood groups the best known and most widely tested is the 0, A, 

 B, AB series so important in relation to blood transfusion. The blood of every 

 person in the world belongs to one of these four types. They are the phenotypic 

 expressions of three allelic genes — A, B, and 0, the latter recessive to both A and 

 B. Blood group has the genotype 00; blood group A may be the expression of 

 either OA or A A; blood group B may similarly be either OB or BB; and blood 



