Ancient DNA provides evidence of earliest known plague outbreak

The skull of an approximately 10-year-old girl that was discovered at the Ust-Ida burial ground. Photograph: Angela Lieverse View image in fullscreen The skull of an approximately 10-year-old girl that was discovered at the Ust-Ida burial ground. Photograph: Angela Lieverse Ancient DNA provides evidence of earliest known plague outbreak Discovery in Siberia suggests bacterium from raw marmots devastated hunter-gatherer tribes about 5,500 years ago The earliest evidence for an outbreak of plague has been uncovered at late stone age cemeteries in south-eastern Siberia where dozens of hunter-gatherers and their children were buried. Ancient DNA collected from the remains suggests the disease tore through the sparse communities in devastating waves that began about 5,500 years ago, at least two centuries after the bacterium responsible, Yersinia pestis , first emerged. The hunter-gatherers probably became infected after butchering or eating raw marmots , a risky practice that still causes plague deaths today . After spilling over from the chunky ground squirrels, the primary animal reservoir in the area, the disease spread from person to person, decimating families and others in close contact. The work resolves a longstanding mystery of why so many children were among the dead at one cemetery in particular, named Ust-Ida, on the bank of the Angara River north-west of Lake Baikal, the oldest and deepest lake in the world. View image in fullscreen The shared graves uncovered at Ust-Ida predominantly contained the remains of children. Photograph: Vladimiri Bazaliiskii While older hunter-gatherers might have survived past brushes with the disease and gained some immunity, young children were exceptionally vulnerable. At least two-thirds of the dead at two of the cemeteries were under 15 years old. Many who died shared graves with siblings or other family members. “The archaeologists were keen to see whether ancient DNA analysis could shed any light on what happened and it absolutely did,” said Ruairidh Macleod, a research fellow who studies ancient DNA at the University of Oxford. “Getting the result that all these people were dying of plague was extraordinary but super exciting. We really didn’t expect to find this in prehistoric hunter-gatherers.” The international team, including researchers in Copenhagen, Alberta, Cambridge and London, analysed dental pulp in the teeth of skeletons excavated from the cemeteries. The graves typically run parallel to the river, with bodies laid so the heads point downstream. Tests on 42 hunter-gatherers buried at four cemeteries on the Angara river found that 18 of them (39%) contained Y pestis DNA, a higher proportion than is seen in some medieval plague pits. Given the high chance of false negatives, where infections are missed because the DNA is too degraded, the scientists suspect all those buried may have died from plague. Writing in Nature , the researchers describe how the ancient DNA points to two distinct outb