29 November 2013
Ancient Siberian genome reveals origins of Native Americans
In the late 1920s, the skeletal remains of a young boy, believed to be 24,000 years old, were discovered near the village of Mal'ta near Lake Baikal in south-central Siberia. Near the boy's remains were flint tools, a beaded necklace and what appears to be pendant-like items, all apparently placed in the burial as grave goods.
According to results from a DNA study, between 14 and 38% of the ancestry of modern Native Americans came from this boy, with the remainder of the being derived from East Asians. Interestingly, the boy shows little to no genetic affinity to modern populations from the same region.
Kelly Graf, assistant professor in the Department of Anthropology at Texas A&M University, helped extract his DNA. "It shows he had close genetic ties to today's Native Americans and some western Eurasians, specifically some groups living in central Asia, South Asia, and Europe. Also, he shared close genetic ties with other Ice-Age western Eurasians living in European Russia, Czech Republic and even Germany."
The genome indicates that prehistoric populations related to modern western Eurasians occupied a wider geographical range into northeast Eurasia than they do today. The study concludes that two distinct Old World populations led to the formation of the First American gene pool: one related to modern-day East Asians, and the other a Siberian Upper Palaeolithic population related to modern-day western Eurasians.
In a nutshell, the researchers' 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."
"At some point in the past, a branch of east Asians and a branch of western Eurasians met each other and had sex a lot," says Doctor Willerslev, who led the sequencing of the boy's genome, adding that this mixing of genes created people that later populated both North and South America.
Doctor Willerslev says, "The thing that was really mind-blowing was that there were signatures you only see in today's Native Americans," and that are consistent among peoples from across the Americas, implying that it could not have come from European settlers who arrived after Columbus and must reflect ancient ancestry. The discovery also raises new questions about the timing of human entry in Alaska and ultimately North America.
Doctor Pontus Skoglund from Uppsala University, Sweden, one of the lead authors of the study, explains, "Most scientists have believed that Native American lineages go back about 14,000 years, when the first people crossed Beringia into the New World. Our results provide direct evidence that some of the ancestry that characterises Native Americans is at least 10,000 years older than that, and was already present in Siberia before the last Ice Age."
Similar genomic signatures from a 17,000 year-old south-central Siberian reveal human occupation of the region after the Last Glacial Maximum (about 26,000 to 19,000 BP), indicating continuity throughout this period - a significant consideration for the peopling of Beringia, and eventually the Americas some 15,000 years ago.
Edited from EurekAlert!, Nature, Tamu Times (20 November 2013), BioNews Texas (22 November 2013)