Scientists have found evidence of a catastrophic flood that overwhelmed the upper Yellow River valley in China some 4,000 years ago, an event that they say may confirm the historical basis of China’s semi-legendary first dynasty.

Ancient Chinese texts record a mix of historical events and legends. Some records, such as those relating to China’s second and third dynasties, were confirmed in surprising detail when archaeologists turned up inscriptions on oracle bones and ancient bronzes.

But records of the first dynasty, that of the Xia, contain stories of a Great Flood with a Noah-like savior, the Emperor Yu, who gained the mandate of heaven after dredging canals to dispel the floodwaters and make the land safe. Historians have long wondered whether this flood account was a creation-style myth, the folk memory of a real event, or some mixture of the two. Some have dismissed the story of Emperor Yu as a fiction intended to justify centralized rule and, in the absence of any evidence of a massive flood at the time, many have regarded the stories of the Xia dynasty as more myth than history.