A new genetic analysis suggests that ancient people brought the plague to Siberia about 4,400 years ago, which may have led to population collapses there.
That preliminary discovery raises the possibility that plague-induced deaths influenced the genetic structure of Northeast Asians who walked to North America from perhaps 5,500 years ago. If the result is maintained, along with other new discoveries about human population dynamics in the region, it would reveal a more complex ancestry among older travelers than was normally assumed.
A team led by evolutionary geneticists Gülşah Merve Kilinç and Anders Götherström, both from Stockholm University, extracted DNA from the remains of 40 human skeletons previously excavated in parts of eastern Siberia. Among those samples, the DNA of Yersinia pestis, the bacterium that causes plague, was found in two ancient Siberians, researchers reported on Jan. 6 in Science Advances. One person lived about 4,400 years ago. The other date from about 3,800 years ago.
It is unclear how the plague bacterium first reached Siberia or whether it caused widespread infections and death, Götherström says. But he and colleagues found that genetic diversity in their ancient human DNA samples had declined dramatically from about 4,700 to 4,400 years ago, possibly as a result of population collapse.
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The new data coincide with evidence reported in June 2020 in the DNA of the Y. pestis cell in two ancient individuals from the Baikal Lake region of eastern Siberia, dating back some 4,500 years.
The plague may have reached Siberia 4,400 years ago, at a time when Y. pestis was infecting people living in other parts of Eurasia (SN: 10/22/15), says evolutionary geneticist Hendrik Poinar of McMaster University in Hamilton, Canada. who does not participate in the new study. But it is possible that the ancient Siberians were infected with a version of Y. pestis that was not virulent. If so, the bacterium would not kill enough people to alter the genetic structure of Siberians. Genetic data from only two individuals provide little evidence to confirm that they possessed a virulent strain of Y. pestis, Poinar says.
Genetic findings provide a reflection of a number of unknown ancient population changes in that region. Ancient individuals included new research dating back some 16,900 years, shortly after reaching the peak of the last Ice Age, until 550 years ago. The researchers compared the DNA of these ancient Siberians with the DNA of modern humans in different parts of the world and with previous samples of ancient human DNA, mainly from Europe, Asia and North America. These analyzes showed that despite the harsh climate of Siberia, groups near Lake Baikal and more eastern regions mixed with various populations in and out of Siberia from the late Stone Age to the medieval period.
The two pest-carrying Siberians, in particular, came from regions that had undergone significant population transformations for much of the time period shown, the researchers say. Those events may have included migrations of plague-carrying people from outside Siberia. For example, the 4,400-year-old skeleton was found just west of Lake Baikal, a region that has witnessed the emergence of several distinct genetic groups, with roots mostly further west and southwest of Lake Baikal, between about 8,980 and 560 years ago. .