Europeans Were 1st Americans? BBC 2 Special

Abstract:

A striking example of the presence in American Indians of genotypes not from haplogroups A�D is haplogroup X. This haplogroup represents a minor founding lineage that is restricted in distribution to northern Amerindian groups, including the Ojibwa, the Nuu-Chah-Nulth, the Sioux, and the Yakima, as well as the Na Dene�speaking Navajo (Brown et al. ¹⁹⁹⁸). Unlike haplogroups A�D, haplogroup X is also found at low frequencies of ~4% in western Eurasian populations. Despite a shared consensus RFLP haplotype, substantial genetic differences exist between the American Indian and European haplogroup X mtDNAs. Phylogenetic analysis and coalescence estimates for American Indian and European haplogroup X mtDNAs exclude the possibility that the occurrence of haplogroup X in American Indians is due to recent European admixture. They also clearly indicate that the two branches/subgroups are distantly related to each other and that considerable genetic substructure exists within both groups (Brown et al. ¹⁹⁹⁸).

Haplogroup X is remarkable in that it has not been found in Asians, including Siberians, suggesting that it may have come to the Americas via a Eurasian migration. The virtual absence of haplogroup X in eastern and northern Asia raises the possibility that some American Indian founders were of European ancestry. In that case, as it has been proposed, haplogroup X was brought to America by the eastward migration of an ancestral white population, of which no trace has so far been found in the mtDNA gene pool of modern Siberian/eastern Asian populations (Brown et al. ¹⁹⁹⁸).

To extend the survey of Asian mtDNAs for the presence of haplogroup X, we screened the mtDNAs of a total of 790 individuals for the RFLP markers (−1715 DdeI, −10394 DdeI, +14465 AccI, and +16517 HaeIII) that define this lineage. These individuals comprised 10 aboriginal Siberian populations: Buryats (n=105), Tuvinians (n=111), Koryaks (n=35), Evens (n=65), Yakuts (n=62), Khakassians (n=54), Shors (n=42), Sojots (n=34), Altaians (n=202), and Evenks (n=80). All individuals belonged to the indigenous population of the regions studied, were unrelated, and stated that their maternal grandmother had been born in the area considered for this study.

Haplogroup X mtDNAs were detected only in Altaians, at a frequency of 3.5%. The haplogroup X status of these haplotypes was confirmed through HVSI and HVSII mtDNA sequencing (table 1). All Altaian X mtDNAs harbored the consensus haplogroup X motif: −1715 DdeI, +14465 AccI, +16517 HaeIII, 16189C, 16223T, 16278T, 73G, 153G, 195C, 263G, relative to the Cambridge reference sequence (Anderson et al. ¹⁹⁸¹) and differed from each other by length-polymorphism mutations at nucleotide positions 16193, 309, and 315. One of these X mtDNAs (ALT16) also harbored a 215G variant (table 1) that has not been observed in either American Indian or European X haplotypes. It should also be noted that none of the Altaian X mtDNAs harbored the 225A variant, which is a marker for a major part of haplogroup X (Brown et al. ¹⁹⁹⁸).

The Altai region was populated during the Lower Paleolithic, and there is ample evidence of settlement during the Middle Paleolithic. It was proposed by anthropologists that, at least from the Neolithic, the territories of Altai and Sayan region were populated by mixed tribes with Caucasoid and Mongoloid anthropological features, but later they were replaced by Mongoloid populations of central Asian origin (Alexeev and Gohman ¹⁹⁸⁴). The analysis of the tribal structure of Southern Altaians has shown that the present-day Altaians have retained their native language and ethnic identity. They have begun to mix with other ethnic groups (mostly Russians and Kazakhs) only recently, so the interethnic admixture is estimated to be <5% (Luzina 1987; Osipova et al. ¹⁹⁹⁷). The haplogroup X mtDNAs have not been found in populations of central Asia, including Kazakhs, Uighurs, and Kirghizs (Comas et al. ¹⁹⁹⁸). Since the frequency of haplogroup X in Russians is extremely low (3 of 336; Orekhov et al. ¹⁹⁹⁹; Malyarchuk and Derenko ²⁰⁰⁰; authors� unpublished data), the recent European admixture cannot explain the presence of haplogroup X in the Altaians. Hence, the results of the present study allow us to suggest that haplogroup X was the part of the ancestral gene pool for Altaian populations, being found both in northern and southern Altaians