Origin mystery solved: The Euphrates River in Mesopotamia was the lifeline of early advanced civilizations. But how it came about has been controversial until now. Now new analyzes show: The two predecessor rivers of the Euphrates did not originally flow into the Persian Gulf, but ended in the eastern Mediterranean around 5.4 million years ago – at a time when this sea was almost dry. Only then did the flow of the rivers gradually shift to the southeast and they joined to form the Euphrates, as a team reports in “Nature Geoscience.”
The Euphrates River in Mesopotamia, along with the Tigris, is considered the cradle of civilization. The beginnings of agriculture and later, more than 5,000 years ago, the first advanced civilizations of humanity developed in the fertile Mesopotamian region. The great empires of the Sumerians, Babylonians and Assyrians were located there and the Sumerian city of Uruk, located on the banks of the Euphrates, is even considered one of the first megacities on earth. As early as the end of the 5th millennium BC, up to 20,000 people lived there, later up to 50,000.
Two opposite scenarios
But how the Euphrates, which is now around 3,000 kilometers long, became the lifeline of the Second River country remains unclear. “According to ancient Mesopotamian creation myths, the Euphrates was formed by Enkidu, the god of wisdom and water, when the world was created,” said Andrew Madof of Chevron in Texas and his colleagues. However, how old the Euphrates actually is and how its course has changed over time has been controversial. However, geological data already suggested that the river could not be older than around ten million years.
“There are currently two contrasting hypotheses to explain the evolution of the Euphrates river system,” report Madof and his team. Some geologists believe that the Ur-Euphrates or its predecessor rivers originally ended in Anatolia or perhaps even in the Mediterranean. According to the second hypothesis, the original Euphrates flowed southeast and ended in the deserts of the Arabian Peninsula.
Who created the river sediment deposits in the Mediterranean?
In order to clarify which of these two scenarios applies, Madof and his colleagues have now evaluated extensive seismic and tectonic data from the Middle East. They also examined deposits of ancient river sediments in the eastern Mediterranean that were deposited during the Great Messinian Salinity Crisis around 5.4 million years ago – the time when the connection between the Mediterranean and the Atlantic was blocked and the Mediterranean gradually dried out.
These mighty deposits, called Handere and Nahr Menashe, show that during this time large rivers from the east must have flowed into the almost dry Mediterranean basin. However, until now it was unclear where these rivers came from. Madof and his team have now used their data and geological and fluviodynamic models to investigate whether there could have been a connection to the Euphrates or its predecessors.
Estuary into the Mediterranean
As the team found, the two headwater rivers of the Euphrates – the Karasu and the Murat – flowed separately around five million years ago. “Our results show that the Paleo-Karasu and the Paleo-Murat formed largely parallel systems flowing from northeast to southwest in the late Miocene,” report the researchers. “These two river systems extended from the headwaters to a region that today lies off the coast of Türkiye and Syria.”
But this means that the two precursors of the Euphrates once flowed into the Mediterranean – exactly where the mighty sediment deposits from the era of the Messinian salinity crisis lie today. “To this day, riverbeds connect the upper reaches of the Karasu and Murat rivers with the Handere and Nahr-Menashe formations,” Madof and his team write. These sedimentary layers lie exactly where these two headwater rivers of the Euphrates once flowed into the Mediterranean basin.
According to the researchers’ reconstructions, the mouth of the Paleo-Murat was only around 25 kilometers north of the Paleo-Nile around five million years ago. “This was probably the shortest distance that these two rivers traveled throughout Earth’s history,” the team said.
As much water as the Nile and Rhône combined
Also surprising: Although the climate was rather dry during the drying phase of the Mediterranean, the Paleo-Karasu alone carried a similar amount of water at its mouth as today’s Nile. The Paleo-Murat transported about as much water as the present-day Rhône. “This seemingly paradoxical result suggests that precipitation and temperatures appeared to fluctuate greatly at that time – even at the level of individual river basins,” explain the researchers.
Even though it hardly rained on the Mediterranean at that time, the prehistoric Euphrates forerunners apparently received enough water in their headwaters and along their course to grow into powerful rivers. Until around 5.33 million years ago, their water flowed into the Mediterranean basin. Afterwards, tectonic processes changed the topography of this region, meaning that the two rivers no longer reached the Mediterranean. Instead, they initially ended in large lake landscapes on the Anatolian Plate.
The birth of the Euphrates
Around 3.6 million years ago, the Euphrates was born: the Anatolian plate rose and diverted the two previous rivers. The course of the Paleo-Murat shifted further and further southeast onto the Arabian Plate until it finally flowed into the Persian Gulf. Around 1.6 million years ago, Murat and Karasu united and formed the modern Euphrates.
“Our results show that this historically important river arose from two different river systems that temporarily flowed into the Mediterranean basin, crossed four tectonic plates over time, merged and finally flowed into the Persian Gulf,” write Madof and his colleagues. “These findings give us deeper insights into the geological processes that ultimately made one of the oldest civilizations on earth possible.”
Source: Andrew Madof (Chevron, Houston) et al., Nature Geoscience, 2026; doi: 10.1038/s41561-026-01962-x