What can Mitochondrial DNA reveal about the Americas first inhbitants?
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Genetic variations among Native Americans provide further clues to who first populated the Americas and when they arrived.
Anthropologists have long speculated on the origins of the native populations in the Americas. One of the more recent theories holds that three distinct waves of immigrants--corresponding to three proposed linguistic groups among Native Americans (Amerind, Na-Dene and Eskaleut)--crossed the Bering strait from Asia no earlier than 13,000 years ago. Molecular anthropologist Theodore Schurr’s research on genetic variation in the mitochondrial DNA of native populations in Asia and the Americas casts some doubt on this view. His research suggests that the first Americans may have come to the New World more than 30,000 years ago. Although there is concordance between the linguistic and genetic affinities of Na-Dene Indians and Eskimo-Aleuts, this type of linkage is less robust for the so-called Amerinds. According to Schurr the genetic evidence is, instead, more consistent with a complex migration pattern involving at least two ancient expansions of ancestral populations who may have come from widely separated parts of the Asian continent, as well as the re-expansion of Beringian populations into the New World following the last period of glaciation.
Figure 4. Distribution of haplogroup frequencies (pie charts) among Amerindian populations does not correspond in any simple way to language-group affiliations, suggesting that a tripartite model of migration to the New World (based on three hypothesized language groups) may be too simple. However, virtually all of the northern Na-Dene mtDNAs belong to haplogroup A, whereas those of the southern Na-Dene also include some from haplogroups B, C and D, indicating that the southern populations have mixed with the neighboring Amerindian populations since their arrival in the American Southwest some 500-to-1, 000 years ago. Certain other trends are also evident: Haplogroup A declines in frequency from north to south, whereas haplogroups C and D increase in frequency. By contrast, there is no obvious clinal distribution for haplogroup B (aside from its absence in northern North America). Whether these distributions reflect the original pattern of settlement in the Americas or subsequent genetic differentiation is not entirely clear.
Genetic variations among Native Americans provide further clues to who first populated the Americas and when they arrived.
Anthropologists have long speculated on the origins of the native populations in the Americas. One of the more recent theories holds that three distinct waves of immigrants--corresponding to three proposed linguistic groups among Native Americans (Amerind, Na-Dene and Eskaleut)--crossed the Bering strait from Asia no earlier than 13,000 years ago. Molecular anthropologist Theodore Schurr’s research on genetic variation in the mitochondrial DNA of native populations in Asia and the Americas casts some doubt on this view. His research suggests that the first Americans may have come to the New World more than 30,000 years ago. Although there is concordance between the linguistic and genetic affinities of Na-Dene Indians and Eskimo-Aleuts, this type of linkage is less robust for the so-called Amerinds. According to Schurr the genetic evidence is, instead, more consistent with a complex migration pattern involving at least two ancient expansions of ancestral populations who may have come from widely separated parts of the Asian continent, as well as the re-expansion of Beringian populations into the New World following the last period of glaciation.
Figure 4. Distribution of haplogroup frequencies (pie charts) among Amerindian populations does not correspond in any simple way to language-group affiliations, suggesting that a tripartite model of migration to the New World (based on three hypothesized language groups) may be too simple. However, virtually all of the northern Na-Dene mtDNAs belong to haplogroup A, whereas those of the southern Na-Dene also include some from haplogroups B, C and D, indicating that the southern populations have mixed with the neighboring Amerindian populations since their arrival in the American Southwest some 500-to-1, 000 years ago. Certain other trends are also evident: Haplogroup A declines in frequency from north to south, whereas haplogroups C and D increase in frequency. By contrast, there is no obvious clinal distribution for haplogroup B (aside from its absence in northern North America). Whether these distributions reflect the original pattern of settlement in the Americas or subsequent genetic differentiation is not entirely clear.
posted by Nagafangzahne at 12:02 PM
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