EVOLUTION, GENETICS, ANTHROPOLOGY — MOURANT 507 



This investigation was of importance not simply as marking the 

 discovery of one particular anthropological character, but as being 

 the first application to anthropology of a totally new method, the study 

 of gene distributions : since there was no necessary distinction between 

 the individuals of one population and of another, the populations 

 themselves became the units of study, and statistical methods, which 

 could still perhaps be regarded as an extra embellishment in classical 

 anthropometric work, became an essential feature of the new type 

 of investigation. 



The blood groups have certain other advantages as anthropological 

 characters. They are fixed for life, at the moment of conception, by 

 the genetical constitution of the individual. Also, unlike such features 

 as the size of various parts of the body, they are unaffected by the 

 subsequent history of the individual (apart from very rare cases, 

 amounting to no more than a few per million of the population, who 

 change their apparent blood group as a result of severe malignant 

 disease). Moreover, while the visible characteristics of the body, and 

 especially the color of the skin, have become associated in some 

 quarters with racial prejudice, and allegations of inferiority and 

 superiority, the blood groups have hitherto gathered no such unsci- 

 entific accretions. 



The medical importance of the blood groups, and the intrinsic inter- 

 est of a new method of studying human populations, rapidly led to 

 the publication of large bodies of blood-group frequency data, and in 

 1939 Boyd, who had himself performed large numbers of tests, was 

 able to extract from the literature, and to compile and publish in the 

 form of tables, the results of testing about one million individuals. 



Until the year 1927 only the blood groups O, A, B, and AB were 

 known. To these we shall now refer as belonging to the ABO system. 

 In that year Landsteiner and Levine announced the discovery of three 

 new blood groups, M, N, and P. The methods which they used, and 

 which are used for the determination of all the blood groups, are 

 technically similar, though the reagents are different, but when their 

 mode of inheritance is examined the blood groups are found to fall 

 into a number of genetical systems, those already named forming the 

 ABO, MN, and P systems, the second of which has since been expanded 

 to form the MNSs system. While the groups of the different systems 

 may resemble one another biochemically, those of one system are as 

 distinct and separate from those of another in their inheritance as are, 

 for instance, hair color and head shape. In a given population there 

 may indeed be a preponderance of people with some particular com- 

 bination of hair color and head shape (each admittedly more complex 

 genetically than the blood groups) but when we study the mode of 

 inheritance within the population, we find that these two types of 



