The Ptolemaic Kingdom was a prosperous time in Egypt’s ancient history, nearly three centuries from 305 B.C. to 30 B.C. that saw the reign of Queen Cleopatra VII and the construction of the Great Library and the Lighthouse of Alexandria.

But during the period there were also several bloody Egyptian revolts against the ruling Greeks. Now, a team of historians and climate scientists say in a study published Tuesday that the unrest and uprisings may have been tied to volcanic eruptions that triggered climatic changes.

Eruptions across the globe may have suppressed monsoons, the scientists said, diminishing the annual river floods and leading to food shortages. Because 70 percent of the world’s population today similarly relies on monsoon-dependent agricultural systems, the findings may warn of what might happen in a volcanically active future.

Today, humanity lives during a relatively quiet volcanic period. The largest eruption to affect the climate in recent memory was the 1991 Pinatubo event in the Philippines. But things were much different during the Ptolemaic era.