The fall of Cleopatra’s Egypt to Augustus, the first Roman emperor, is usually told as a melodramatic power struggle between elites on the world stage.

Cleopatra famously forged a doomed political alliance with the Roman general Mark Antony, who was also her lover. But when their combined forces were defeated at the battle of Actium, the pair killed themselves and Egypt became a province of the newly formed Roman empire.

However, a new analysis suggests the seeds of Cleopatra’s defeat may have been sown a decade earlier by environmental forces beyond her control. It links a massive volcanic eruption – which probably happened somewhere in the Tropics, although the team is not sure – with severe disruption to the seasonal flooding of the Nile, and devastating consequences for Egyptian agriculture.

The study, based on evidence from ice-core records of eruption dates, the Islamic Nilometer (an ancient history of Nile water levels) and Ancient Egyptian documentation of social unrest, suggests that a giant volcanic eruption in 44BC may have suppressed rainfall, leading to famines, plague and social unrest. Ultimately, the authors argue, this may have weakened Cleopatra’s hold on power a decade before her defeat in 30BC, changing the course of world history.