Reveal the mystery of the collapse of ancient civilizations through the old skeletons

Thousands of years ago, across the Eastern Mediterranean, many Bronze Age civilizations made definite turns for the worse at about the same time.

Besides climate change and migration, disease also contributed to the collapse of many ancient civilizations.

The Kingdom of Ancient Egypt and the Akkadian Empire both collapsed, accompanied by a social crisis that spread throughout the Ancient Near East and the Aegean, marked by population declines, frozen trade, and great cultural change.

As we often hear, the main cause of this downfall is climate change and the loyalty of the generals to the King of Civilizations. But scientists have found a new culprit by studying some of the remains of ancient people.

The team, led by paleontologist Gunnar Neumann, of the Max Planck Institute for Evolutionary Anthropology, Germany, analyzed skeletons unearthed at the burial site in the Hagios Charalambos cave on Crete, Greece. found genetic evidence of the bacteria responsible for two of the most important diseases in history - typhoid and bubonic plague.

The widespread illness caused by these pathogens cannot be considered a contributing factor to the social changes that were common around 2200 to 2000 BC, experts say.

"The emergence of these two virulent pathogens at the end of the Early Minoan period in Crete underscores the need to reintroduce infectious diseases as an additional factor that may have contributed to the transformation of societies. early complex societies in the Aegean and beyond," the authors said.

Yersinia pestis is a bacterium that causes plague, resulting in tens of millions of deaths, most of which occurred during the course of three devastating global pandemics spanning centuries.

It is therefore difficult to assess its impact before the Justinian plague, which began in AD 541. But recent scientific and technological advances, especially the recovery and sequencing of ancient DNA from old bones, have revealed some lost history.

Experts suspect that the bacteria have been infecting humans since at least the Neolithic period.

Last year, scientists revealed a hunter-gatherer from the Stone Age likely died of bubonic plague, before we had evidence of the disease and let it spread. epidemic.

However, the genomic evidence recovered so far has been from colder regions. Little is known about its impact on ancient societies in warm climates, such as those in the Eastern Mediterranean, because DNA degrades with higher temperatures.

The bacterium Yersinia pestis is the cause of the plague (Image: NIH).

So Neumann and his team went to dig up bones recovered from a site on Crete known for its stable and cool conditions. They recovered DNA in the teeth of 32 individuals who died between 2290 and 1909 BC and discovered genetic data suggesting the presence of the bacteria.

These are Yersinia pestis bacteria and two strains of Salmonella enterica - a bacteria that often causes typhoid fever. This discovery suggests that both pathogens were present from this time and could be transmitted in Bronze Age Crete.

The main difficulty in the research process is that, each family (bacteria) found is now extinct, making it more difficult than ever to identify infections that might have affected the community at that time. .

The lineage of Yersinia pestis they discovered probably couldn't be transmitted by fleas - one of the characteristics that makes other strains of bacteria so contagious in human populations.

Verto fleas carry their version of the plague; Humans are infected when the bacteria enter the lymphatic system through its bite. Therefore, the transmission route of this ancient form of bacteria may have been different and caused a different form of plague.

The Salmonella enterica strains also lack key traits that contribute to severe disease in humans, the researchers say, hence virulence (the bacteria's way of initiating infection and pathogenicity) and pathways. The transmission of both pathogens is still unknown.

However, the discovery shows that they already exist and circulate, especially in areas of Crete with high population density, which can spread into a pandemic.

Although it is uncertain whether Yersinia pestis or Salmonella enterica was the sole culprit for the social changes observed in the Mediterranean in the late 3rd millennium BC.

"We suggest that evidence from ancient DNA studied carrying infectious diseases should be considered as an additional contributing factor to the collapse of civilizations, along with civilizations," the authors said. with climate and migration issues".

Because diseases such as bubonic plague and typhoid leave no marks on bones, they are not frequently recorded in the archaeological record.

The team suggests that a more detailed genetic screening of many ancient remains from the Eastern Mediterranean could help uncover how these diseases affected the civilizations that lived there.