Alu insertion polymorphisms in Native Americans and related Asian populations

Background: Alu insertions provide useful markers for the study of inter- population affinities and historical processes, but data on these systems are not numerous in Native Americans and related populations. Aim: The study aimed to answer the following questions: ( a) do the population relationships found agree with ethnic, historical and geographical data? and ( b) what can heterozygote levels and associated results inform us about the events that led to the colonization of the New World? Subjects and methods: Twelve Alu insertion polymorphisms were studied in 330 individuals belonging to South American Native, Siberian and Mongolian populations. These data were integrated with those from 526 persons, to ascertain the relationships between Asian, Northern Arctic and Amerindian populations. Results: A decreasing trend concerning heterozygosities and amount of gene flow was observed in the three sets, in the order indicated above. Most results indicated the validity of these subdivisions. However, no clear structure could be observed within South American Natives, indicating the importance of dispersive ( genetic drift, founder effects) factors in their differentiation. Conclusions: The answers to the questions are: ( a) yes; and ( b) an initial moderate bottleneck, intensified by more recent historical events ( isolation and inbreeding), can explain the current Amerindian pattern of diversity.