Archeologia preistorica e analisi del DNA mitocondriale nella questione del popolamento delle Americhe

Native Americans belong to one of the few extant human groups whose ancestors entered a vast uninhabited area and then apparently remained isolated from other human contacts for thousands of years. They are descendants of peoples, who, after their expansion to the Americas, underwent through a rapid process of tribal radiation and isolation, localised genetic and cultural differentiation, and adaptation to a variety of different environmental conditions. Although there is consensus that the provenance of the ancestral Native Americans was North-Eastern Asia, the diversity of opinions on the time of the earliest human entry into the Americas, and the number of migratory events has often been accompanied by an acrimonious debate. As a broad generalization, the discussants of the times of human colonization of the New World can be divided into two camps, one favoring an "early" entry [more than approximately 30.000 years before present (YBP)] , the other favoring a "late" arrival (less than approximately 13,000 YBP). As for the number of migratory events, the debate is between those who favor a single migration from Asia, followed by an "in situ" genetic and cultural differentiation, and those who favour multiple migration hypotheses. In this paper, we summarize the data concerning these issues that we have recently obtained through studies affering to two different and interrelated disciplines: molecular genetics and pre-historical archaeology. These data are strongly supportive of an "early" human colonization of the Americas, and indicate that the genetic and cultural heterogeneity of modern Native Americans is partially attributable to multiple migrations from Asia.