Chapter 6 Molecular Markers in Anthropological Genetic Studies

In 1973, a chapter entitled 'The use of genetic markers of the blood in the study of the evolution of human populations', was published in the first volume that attempted to synthesize the field of anthro­ pological genetics (Crawford, 1973). This chapter defined genetic markers as 'discrete segregating, genetic traits which can be used to characterize populations by virtue of their presence, absence, or high frequency in some populations and low frequency in others' (Crawford, 1973: 38). This definition similarly applies to molecular markers, which are segregating regions of DNA, present in some populations but absent or infrequent in others. The 1973 chapter summarized the available genetic markers of the blood that could be used for the measurement of evolutionary processes and the characterization of human population structure. The list of available polymorphic loci included 16 blood groups, 11 red blood cell proteins, 10 serum proteins and 3 white cell and platelet systems. These 'riches' of available variation of the blood followed 70 years of research on the blood group systems (since Karl Landsteiner's original work in 1900), and Oliver Smithies (1955) development of zone electrophoresis for the separation of specific proteins from mixtures such as the serum of the blood (Landsteiner and Levine, 1927). At the time the first volume in anthropological genetics was compiled, the physiological functions of blood groups were unknown, other than their involvement in blood transfusion and some suspect statistical associations with disease. The role of DuffY blood group as a resistance factor to Plasmodium vivax in Africans was not known