Plague outbreaks dating back to around 5,500 years ago documented in hunter-gatherer communities from southeast Siberia are described in a paper published in Nature. The findings, based on an analysis of ancient DNA, may be the oldest known evidence of the plague and could shed light on its origins.

The skull of a 9-11 year old girl

Source: Angela Lieverse

The skull of a 9-11 year old girl who died and was buried along with plague victims at the Ust’Ida I burial ground.

Plague accounts for some of the deadliest disease outbreaks in history; the study of ancient DNA has aided our understanding of the origin and evolution of the disease. Previous research had identified Yersinia pestis, the bacteria that causes plague, in prehistoric Europe.

Some of the oldest documented strains date back up to 5,300 calibrated years before present (5300 cal BP), but these strains may have lacked classic virulence genes (sequences that cause disease).

Ust’Ida I Burial #44

Source: Vladimiri Bazaliiskii.

Ust’Ida I Burial #44; this shared grave contains three individuals, two of which were identified from ancient DNA as half-sisters (with a shared mother), aged 9-10 years old and 5-6 years old. The third occupant of the shared grave is a boy aged 11-12 years old, who is not closely related to either of the half-sisters, but was buried at the same time in the same grave as them, and was found to have plague DNA.

Ruairidh Macleod, Eske Willerslev, and colleagues analysed ancient DNA from 42 hunter-gatherers from four cemeteries around Lake Baikal in Siberia. They identified Y. pestis in 18 individuals, at higher levels than any other pathogen, which indicated two separate plague outbreaks dated to 5520–5265 cal BP and 5315–4235 cal BP.

Family groups

The authors reconstructed kinship among the individuals and were able to show that small family groups were affected, aligning with human-to-human transmission of the disease. They found related individuals buried in separate graves, suggesting they died in different events and not in a single outbreak.

They also indicate that the most acute infections appear to have occurred in children aged 8–11 years. They note that the Y. pestis genomes associated with these two outbreaks differ from currently known ancient and modern plague strains and suggest that this particular strain emerged before approximately 5,700 years ago.

artistsI

Source: Kelvin Wilson.

Artistic reconstruction of Baikal hunter-gatherers from 5500 years ago burying victims of plague.

The authors suggest that their findings demonstrate that plague outbreaks occurred in prehistoric hunter-gathers hundreds of years before infections were observed in Neolithic populations. They note that this challenges the idea that high population densities and the agriculture transition observed during the Neolithic were necessary for plague epidemics.

Topics