EVOLUTION, GENETICS, ANTHROPOLOGY — ^MOURANT 511 



among New World populations of Mediterranean and African an- 

 cestry. It is not known whether they belong to either of the genetical 

 systems mentioned above, which determine tlie production of par- 

 ticular abnormal types of hemoglobin, but they cause a disturbance of 

 normal hemoglobin production broadly similar to that produced by 

 the sickle-cell hemoglobin gene, the heterozygotes being clinically 

 almost normal and the homozygotes suffering from a severe hemolytic 

 anemia. Here again it is thought that the heterozygotes have an 

 advantage over normal persons in being more resistant to malaria, but 

 the process is less fully understood than in the case of the sickle-cell 

 condition. Anthropologically, thalassaemia is of similar value in 

 classifying populations to the more specific hemoglobin abnormalities. 



GENETICAL CHARACTERS IN ANTHROPOLOGY 



Bearing in mind the relatively simple model provided by the hemo- 

 globins we are now in a position to consider more fully and critically 

 the contribution to anthropology which has been made, and that which 

 can in the future be made, by the study of the blood groups and 

 other genetically simple biochemical characters. 



All the 11 major blood-group systems have contributed to anthro- 

 pological knowledge, but three of them, the original ABO system of 

 Landsteiner and the JMNSs and Kh systems, have made by far the 

 greatest contributions. Because of their earlier discovery, their medi- 

 cal importance, and the ready availability of the testing reagents, far 

 more information is available about the distribution of the ABO 

 groups (Mourant et al., 1958) than of the others (Mourant, 1954). 

 On the basis of blood-group frequencies as a whole the world can be 

 divided into about six major regions differing markedly in frequencies 

 for nearly all systems. Within each region the frequencies of the 

 MNSs and Eh groups show highly characteristic patterns with rela- 

 tively little fluctuation, whereas those of the ABO groups vary con- 

 siderably even within comparatively small areas such as Great Britain. 

 The ABO groups appear to have been subject to more intense and 

 rapid differential processes of natural selection than those of the 

 other systems. The comparative constancy of the frequencies of the 

 MNSs and Rh gi'oups may be due to the relative absence of selection, 

 or to balance of selective effects, but the existence of an absolutely 

 higher selection pressure on the ABO groups is in agreement with 

 what we know more directly about the relationship of blood groups to 

 diseases. 



The best known example of association between blood groups and 

 disease is that shown by hemolytic disease of the newborn, which is 

 the result of blood-group incompatibility between mother and foetus, 

 most frequently with respect to the Rh system (Levine, Katzin, and 



