Climate-Changing Volcanic Eruptions May Have Helped Topple Cleopatra

Volcanic eruptions around the world may have interrupted agricultural production along the Nile, setting off the social unrest that preceded the collapse of the Ptolemaic dynasty.

It's a mystery that's perplexed Egypt scholars for hundreds of years: What ultimately caused the collapse of the 300-year Ptolemaic dynasty and the downfall of its last ruler, the queen Cleopatra?

It turns out that the answer — or part of the answer, anyway — appears to be volcanoes.

An international team of historians and climate scientists published research this week in the journal Nature Communications suggesting ancient volcanic eruptions changed the course of history in Africa and the Middle East. It's a twisty tale, concerning class revolt, ancient papyrus records, ice core samples, tropical volcanoes, and the annual flooding of the river Nile.

It helps to have a little background: The Ptolemaic dynasty in Egypt (305-30 BC) relied heavily on the seasonal flooding of the Nile for agriculture. But the Nile was famously unreliable, and when the river didn't flood, crops died, triggering famines, plagues, and social unrest.

Historians know this thanks to various artifacts that show both the history of the Nile's water levels and the history of major political crises and uprisings.

One of those historians is Joseph Manning of Yale University, who co-authored the new study with Francis Ludlow, a climate historian at Trinity College Dublin. While Manning's work focuses on Egyptian history, Ludlow's specialty is tracking major volcanic eruptions throughout history.

The idea for their unique collaboration was to compare timelines of Egyptian unrest with geological records that reveal the timing of major volcanic eruptions. Their conclusion: It's likely that violent volcanic eruptions triggered climate changes that directly impacted the Nile — which in turn may have led to the social upheaval that doomed Cleopatra and the Ptolemaic dynasty.

“My specialty, as a climate historian, is to concentrate upon how we can extract information on past climate conditions from both natural and human archives,” Ludlow told Seeker. “Natural archives might include tree rings or ice cores, and human archives would include written records and even archaeological evidence.”

Using computer simulations and historical measurements of the Nile River, Ludlow, Manning, and their colleagues discovered that poor flood years on the Nile lined up over and over again with major volcanic eruptions around the world. The evidence suggests that the volcanic activity cooled the atmosphere, suppressing rainfall and preventing the Nile from flooding.

Digging even deeper into the historical record, Manning was able to determine that volcanic eruptions preceded several major political and economic events during the Ptolemaic period. For instance, a major eruption in 247 BC was followed by a revolt that caused the army of Ptolemy III to withdraw from a Middle Eastern campaign and return home. The revolt was likely due to crop failure, which was almost certainly caused by the Nile failing to flood.

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A similar scenario occurred in 44 BC, which led to an outbreak of famine and disease that weakened the rule of Cleopatra.

The researchers are quick to note that much of the cause-and-effect linkage is supposition, and that climate changes are just one of many factors that can contribute to major events in history.

“Connecting climatic changes to complex social and political events like the collapse of a dynasty needs to be done cautiously and with a full recognition of the historical context in which many other factors will also inevitably have played an important role,” Ludlow said.

Still, the concurrence of volcanic activity with Nile river failures — and subsequent civil unrest — is remarkably precise and very unlikely to be simple coincidence, researchers said. The trick is in noticing them in the first place. All the clues were there in the historical record, Manning said, but it took a team of scholars to piece them together.

“It's important to work in this truly interdisciplinary way in order to make progress,” Manning said.

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Ludlow and Manning intend to continue their collaboration, looking into Egypt during the Roman and Byzantine periods, and perhaps branching out to the Near East and India. The researchers note that their work could have implications in the modern era, as well.

“The 21st century has been lacking in explosive eruptions… but that could change at any time,” Ludlow said. “The potential for this needs to be taken into account in trying to agree on how the valuable waters of the Blue Nile are going to be managed between Ethiopia, Sudan, and Egypt.”

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