Admixture studies in Latin America: From the 20th to the 21st century

The present study is a review of admixture studies in Latin America, an int eresting subject because of the unique history of the area, in which popula tions from 3 different origins had contact and intercrossed. The most often used methods of analysis of admixture in Latin America and some problems r elated to them, such as the determination of the parental populations and s election of genetic markers, are briefly reviewed. Several sources of data for admixture studies (surnames, quantitative traits, proteins, and molecul ar information) are summarized. The results obtained using protein systems and blood groups, the most often used markers in Latin America, are conside red. They are classified according to their application in 3 groups of popu lations: urban centers, native Americans, and African-descended subjects. T he data show that almost every population is dihybrid or trihybrid, and whe n African influence is not detected, it is probably due more to the method than to an absence of that contribution. A special section is dedicated to the direction of gene flow, and results about directional mating based on m tDNA, Y-chromosome, and nuclear DNA or proteins are also given, From these studies it is possible to conclude that Amerindian admixture came mainly fr om female lineages, but it is difficult to establish what happened with the African contribution, A last subject considered is the relation between in terethnic crosses and diseases; it is easy to analyze that relation when th e pathological condition is related to a unique allele, bur when complex di seases are considered, the results are not as clear because of the influenc e of nongenetic factors, Finally, the perspectives for admixture studies in the 21st century are considered, and some attempts to predict their future in Latin America are made.