Insuperable
11-20-2013, 07:26 PM
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12736.html
The origins of the First Americans remain contentious. Although Native Americans seem to be genetically most closely related to east Asians1, 2, 3, there is no consensus with regard to which specific Old World populations they are closest to4, 5, 6, 7, 8. Here we sequence the draft genome of an approximately 24,000-year-old individual (MA-1), from Mal’ta in south-central Siberia9, to an average depth of 1×. To our knowledge this is the oldest anatomically modern human genome reported to date. The MA-1 mitochondrial genome belongs to haplogroup U, which has also been found at high frequency among Upper Palaeolithic and Mesolithic European hunter-gatherers10, 11, 12, and the Y chromosome of MA-1 is basal to modern-day western Eurasians and near the root of most Native American lineages5. Similarly, we find autosomal evidence that MA-1 is basal to modern-day western Eurasians and genetically closely related to modern-day Native Americans, with no close affinity to east Asians. This suggests that populations related to contemporary western Eurasians had a more north-easterly distribution 24,000 years ago than commonly thought. Furthermore, we estimate that 14 to 38% of Native American ancestry may originate through gene flow from this ancient population. This is likely to have occurred after the divergence of Native American ancestors from east Asian ancestors, but before the diversification of Native American populations in the New World. Gene flow from the MA-1 lineage into Native American ancestors could explain why several crania from the First Americans have been reported as bearing morphological characteristics that do not resemble those of east Asians2, 13. Sequencing of another south-central Siberian, Afontova Gora-2 dating to approximately 17,000 years ago14, revealed similar autosomal genetic signatures as MA-1, suggesting that the region was continuously occupied by humans throughout the Last Glacial Maximum. Our findings reveal that western Eurasian genetic signatures in modern-day Native Americans derive not only from post-Columbian admixture, as commonly thought, but also from a mixed ancestry of the First Americans.
http://www.bloomberg.com/news/2013-11-20/american-indian-origins-complicated-by-ancient-boy-s-dna.html
American Indians may have a more complex pool of ancestors than scientists once thought, according to a 24,000-year-old arm bone found in Siberia.
A DNA sample from the bone showed it belonged to a boy who was more closely related to American Indians and people living today in Europe and Western Asia than to East Asians, according to a paper published today in the journal Nature.
The finding may mean that American Indians have European genes that predate Christopher Columbus and subsequent western migrations to the Americas. Most experts have thought that American Indians came from east Asia, so another set of ancestors may need to be accounted for, said Joshua Akey, who specializes in evolutionary genomics at the University of Washington School of Medicine in Seattle.
“There’s been enormous controversy in the origins and ancestry of Native American populations,” Akey, who wasn’t involved in the research, said in a telephone interview. “This study suggests a much more complicated and rich history than previously imagined.”
About 14 percent to 38 percent of American Indian ancestry may have originated from the population to which the Siberian boy belonged, according to today’s report. In fact, when the researchers mapped the bone’s genes, they suggested that all 48 modern American Indian populations were equally related to the boy’s sample.
The finding may also explain why skulls from early American Indian groups have characteristics that don’t fit with East Asian ancestry, wrote the researchers, led by Eske Willerslev of the University of Copenhagen.
Sex Chromosome
The boy’s DNA, from what may be the oldest modern human genome to date, was closest to the hunter-gatherers of the Late Stone Age, from 50,000 to 10,000 years ago. The Y chromosome, the sex chromosome present in men, belongs to an ancestry that predates modern western Eurasians, the study found. There was no close relationship between the sample and modern east Asians.
A second DNA sample, from a 17,000-year-old arm bone also found in Siberia, showed similarities to the older DNA, though it was less reliable, as the genetic material had been contaminated by present-day DNA, the researchers said.
The site where the 24,000-year-old young male’s bones were found is called Mal’ta, for a nearby village in south-central Siberia. The area may be the oldest in Siberia, and was excavated from 1928 to 1958, the authors wrote.
The origins of the First Americans remain contentious. Although Native Americans seem to be genetically most closely related to east Asians1, 2, 3, there is no consensus with regard to which specific Old World populations they are closest to4, 5, 6, 7, 8. Here we sequence the draft genome of an approximately 24,000-year-old individual (MA-1), from Mal’ta in south-central Siberia9, to an average depth of 1×. To our knowledge this is the oldest anatomically modern human genome reported to date. The MA-1 mitochondrial genome belongs to haplogroup U, which has also been found at high frequency among Upper Palaeolithic and Mesolithic European hunter-gatherers10, 11, 12, and the Y chromosome of MA-1 is basal to modern-day western Eurasians and near the root of most Native American lineages5. Similarly, we find autosomal evidence that MA-1 is basal to modern-day western Eurasians and genetically closely related to modern-day Native Americans, with no close affinity to east Asians. This suggests that populations related to contemporary western Eurasians had a more north-easterly distribution 24,000 years ago than commonly thought. Furthermore, we estimate that 14 to 38% of Native American ancestry may originate through gene flow from this ancient population. This is likely to have occurred after the divergence of Native American ancestors from east Asian ancestors, but before the diversification of Native American populations in the New World. Gene flow from the MA-1 lineage into Native American ancestors could explain why several crania from the First Americans have been reported as bearing morphological characteristics that do not resemble those of east Asians2, 13. Sequencing of another south-central Siberian, Afontova Gora-2 dating to approximately 17,000 years ago14, revealed similar autosomal genetic signatures as MA-1, suggesting that the region was continuously occupied by humans throughout the Last Glacial Maximum. Our findings reveal that western Eurasian genetic signatures in modern-day Native Americans derive not only from post-Columbian admixture, as commonly thought, but also from a mixed ancestry of the First Americans.
http://www.bloomberg.com/news/2013-11-20/american-indian-origins-complicated-by-ancient-boy-s-dna.html
American Indians may have a more complex pool of ancestors than scientists once thought, according to a 24,000-year-old arm bone found in Siberia.
A DNA sample from the bone showed it belonged to a boy who was more closely related to American Indians and people living today in Europe and Western Asia than to East Asians, according to a paper published today in the journal Nature.
The finding may mean that American Indians have European genes that predate Christopher Columbus and subsequent western migrations to the Americas. Most experts have thought that American Indians came from east Asia, so another set of ancestors may need to be accounted for, said Joshua Akey, who specializes in evolutionary genomics at the University of Washington School of Medicine in Seattle.
“There’s been enormous controversy in the origins and ancestry of Native American populations,” Akey, who wasn’t involved in the research, said in a telephone interview. “This study suggests a much more complicated and rich history than previously imagined.”
About 14 percent to 38 percent of American Indian ancestry may have originated from the population to which the Siberian boy belonged, according to today’s report. In fact, when the researchers mapped the bone’s genes, they suggested that all 48 modern American Indian populations were equally related to the boy’s sample.
The finding may also explain why skulls from early American Indian groups have characteristics that don’t fit with East Asian ancestry, wrote the researchers, led by Eske Willerslev of the University of Copenhagen.
Sex Chromosome
The boy’s DNA, from what may be the oldest modern human genome to date, was closest to the hunter-gatherers of the Late Stone Age, from 50,000 to 10,000 years ago. The Y chromosome, the sex chromosome present in men, belongs to an ancestry that predates modern western Eurasians, the study found. There was no close relationship between the sample and modern east Asians.
A second DNA sample, from a 17,000-year-old arm bone also found in Siberia, showed similarities to the older DNA, though it was less reliable, as the genetic material had been contaminated by present-day DNA, the researchers said.
The site where the 24,000-year-old young male’s bones were found is called Mal’ta, for a nearby village in south-central Siberia. The area may be the oldest in Siberia, and was excavated from 1928 to 1958, the authors wrote.