A world of differences

The human species is highly variable, and Latin Americans are no exception. In fact, due to the merging of groups that previously had genetically differentiated in other continents, this variability is accentuated. The study of normal variation among humans has a respectable past, going back to the eighteenth century, with scholars such as Carl von Linné (1707–78), Georges L. Leclerc de Buffon (1707–88), and Johann F. Blumenbach (1752–1840). At the beginning the traits considered were mainly morphologic. It was only with the seminal discovery in 1900, by Karl Landsteiner (1868–1943), of the ABO blood groups, that the door was open for the discovery of simple-inherited traits that could provide more rigorous evaluations of such differences, separating the effects of genes from those of their environments.

In terms of methodology, three distinct key developments should be noted. The first was based on immunologic techniques, leading to the discovery of some two dozen blood groups. Their specificity is determined by the chemical structure of the antigen determinants located on proteins and glycoconjugates (glycolipids and glycoproteins). In the mid-1950s, electrophoretic methods (based on the differences in the electric charges of the proteins) were devised; the investigator to be mentioned here is Oliver Smithies. Finally, with the spectacular developments in molecular biology in the 1970s and 1980s, we are now considering the variability present in the genetic material per se (deoxyribonucleic acid, or DNA), and not only its primary product (proteins).

The Latin American microcosm

The first population study on blood groups in Latin America that we could locate was that of Montenegro (1925) in Brazil.