Genetic difference between Europeans and Indians: tissue and blood types.

When Columbus reached America, the continent probably was inhabited by 15 to 30 million natives. Mexico now has 68 different Indian tribes classified from a linguistic point of view; 5 million people speaking different languages are registered. However, the Mexican population is mainly composed of Mestizos (95%), who have a triracial admixture of Caucasian genes coming from the Spanish conquerors, black genes from the African slaves brought by the Spaniards to America, and an Oriental gene-pool derived from the natives. The admixture started around 1500, but at present it may be very difficult to distinguish phenotypically one group from another, and the Mestizos from the Indians. Therefore, polymorphic systems like the major histocompatibility complex (MHC) or several blood markers are very valuable tools and crucial elements to trace human migrations, to define degree of admixture, and to explore the impact of genetics on the epidemiology of the different populations. The distribution of blood group systems throughout western Europe is very homogeneous. In contrast, in the Mongolian the A2 subgroup and the S allele almost disappear compared with European Caucasian. Although homogeneity also exists in Orientals, several groups have a very particular pattern, such as the Senoi from Malay, the Tharons from Burma and the Ainu from Japan. We analyzed four Mexican Indian tribes, and as in Amerindians group 0 is extremely high, almost all are kappa; Fya is increased as in Mongolians, and Dia is an Oriental and Amerindian marker. The distribution of Lu and Kp suggests that the environment might have influenced the variability of these antigens found in Indians.(ABSTRACT TRUNCATED AT 250 WORDS)