Ancient DNA reveals plague was already killing humans 5,500 years ago

Ancient DNA analysis has confirmed that plague was killing humans approximately 5,500 years ago in Siberia, well before the emergence of cities and farming communities. The discovery was made through genetic sequencing of remains from prehistoric hunter-gatherers near Lake Baikal, indicating that highly lethal strains of Yersinia pestis existed long before the medieval outbreaks known from historical records. This finding challenges previous assumptions about the origins and early spread of plague.

Researchers examined human remains from four hunter-gatherer cemeteries near Lake Baikal, recovering and sequencing DNA from ancient teeth. They identified DNA from Yersinia pestis in 18 of 46 individuals, representing nearly 40 percent of the sampled remains. This detection rate exceeds those from some medieval plague sites, suggesting significant outbreaks in prehistoric times.

The study found that early strains of plague carried a unique genetic feature—a superantigen—that could trigger severe immune responses. Unlike later strains, these ancient bacteria lacked some genetic traits associated with flea-borne transmission, indicating that the disease was highly lethal even without the flea transmission mechanism. The presence of many children and young teenagers among the victims, buried over a short period, supports the idea of rapid, deadly outbreaks.

Implications for Understanding the Origins of Plague

This discovery significantly alters the timeline of plague’s history, showing that the disease was already deadly to humans 5,500 years ago. It suggests that plague’s virulence predates its association with fleas and rodents, indicating a different mode of transmission or directly from wild animals like marmots. Understanding this early, highly lethal form of plague can inform current research on the disease’s evolution and potential risks.

Prehistoric Evidence of Deadly Disease in Siberia

Prior to this study, the earliest known plague outbreaks were associated with historical and medieval Europe, with some evidence of earlier presence in Eurasia. Previous genetic studies indicated that ancient strains lacked features enabling efficient flea transmission, leading scientists to believe early plague was less virulent. The new findings from Siberian remains push the origin of deadly plague back by several millennia, highlighting its presence among hunter-gatherer groups before the rise of complex societies.

“Our findings demonstrate that these ancient strains were already highly lethal, even before the bacterium evolved efficient flea-borne transmission.”

— an anonymous researcher

What Aspects of Early Plague Are Still Unknown

It remains unclear how the ancient strains of Yersinia pestis were transmitted among prehistoric humans, especially given the absence of flea-borne transmission features. The precise ecological and behavioral factors facilitating these outbreaks are still under investigation. Additionally, the full extent of the disease’s impact on prehistoric populations and its geographic spread require further research.

Future Research Directions on Ancient Plague Origins

Scientists plan to analyze additional ancient remains from different regions to map the early spread and evolution of plague. Further genetic studies aim to clarify the transmission mechanisms of these ancient strains and assess their relationship to later, more virulent forms. Ongoing research will also explore how early humans interacted with potential animal reservoirs like marmots and other rodents.

Key Questions

How old are the plague strains identified in the Siberian remains?

The strains date back approximately 5,500 years, predating previously known outbreaks by several millennia.

Did early plague spread through fleas like later strains?

It is unlikely, as the ancient strains lacked genetic features associated with flea transmission, suggesting alternative spread mechanisms.

What does this mean for modern understanding of plague?

It indicates that highly lethal forms of plague existed long before the development of flea-borne transmission, which may influence current research on disease evolution and potential risks.

Are these findings relevant to current plague outbreaks?

While the ancient strains differ from modern ones, understanding their virulence and transmission can provide insights into the disease’s history and potential future threats.

Will further ancient DNA studies help clarify plague origins?

Yes, additional genetic analyses of prehistoric remains are expected to shed light on how and where plague first emerged and spread among early human populations.

Source: rss