The Neolithic period, marked by the transition from a hunter-gatherer lifestyle to agriculture and settled communities, was a transformative era in human history. However, the sudden and unexplained disappearance of Europe's first farmers, known as the Neolithic population, has long puzzled archaeologists and historians. Now, a groundbreaking study published in the prestigious journal Nature may have uncovered a crucial piece of the puzzle, the presence of an ancient form of the plague bacterium, Yersinia pestis, among this population.
The study, led by Frederik Seersholm, a postdoctoral researcher at the Lundbeck Foundation GeoGenetics Centre, University of Copenhagen, analyzed ancient DNA recovered from 108 prehistoric individuals unearthed at nine grave sites in Sweden and Denmark. The findings suggest that the plague might have been widespread among the Neolithic farmers, potentially contributing to their mysterious collapse over the span of 400 years.
It's fairly consistent across all of Northern Europe, France and it's in Sweden, even though there are some quite big differences in the archaeology, we still see the same pattern, they just disappear, Seersholm said, highlighting the widespread nature of this phenomenon.
The Neolithic population, who migrated from the eastern Mediterranean and brought agriculture and a settled lifestyle to northwestern Europe around 6,000 to 7,000 years ago, left behind a rich legacy of megalithic graves and monuments, including the iconic Stonehenge. Their sudden disappearance between 5,300 and 4,900 years ago has long been a subject of intense debate among archaeologists, with some attributing it to an agricultural crisis caused by climate change and others suspecting the role of disease.
The study's findings lend credence to the latter hypothesis, as the researchers discovered that forms of the plague bacterium were present in 1 in 6 ancient samples, suggesting that infection with the disease was not uncommon. These plague cases, they are dated to exactly the time frame where we know the Neolithic decline happened, so this is very strong circumstantial evidence that the plague might have been involved in this population collapse, Seersholm said.
Interestingly, the study did not find evidence of a swift and deadly plague epidemic. Instead, the researchers detected three distinct infection events, as well as different variants of the plague bacterium, suggesting a more complex and prolonged interaction between the Neolithic population and the pathogen.
I was also expecting the plague to be exactly the same, like every single DNA base pair would be the exact same, because that's what you would expect if you saw a swift outbreak of disease, but that was not what we found, Seersholm explained.
The researchers hypothesize that the reshuffling of plague genes, which they found in areas associated with virulence, may have affected the pathogen's potency over the generations, potentially explaining why the disease did not immediately wipe out the entire population.
While the study provides compelling evidence for the presence of an ancient form of the plague among the Neolithic farmers, Mark Thomas, a professor of evolutionary genetics at University College London, cautions that the disease may not have been the sole reason for their demise. He suggests that a combination of factors, including poor farming practices, soil exhaustion, and widespread ill health, may have contributed to the Neolithic population's decline.
Nonetheless, this study represents a significant step forward in understanding the complex interplay between human populations and infectious diseases throughout history. By harnessing the power of ancient DNA, researchers have been able to uncover the hidden stories of our past, shedding light on the mysteries that have long eluded us.
