Silk painting of Yu the Great. Public Domain

Thousands of years ago, the legend goes, an ancient people living along the banks of the Yellow River in northern China experienced a flood unlike any before it.

The waters inundated communities and made the land unusable for farming. First one emperor, then another, tried to subdue the floodwaters, but all were unsuccessful — until Yu the Great.

Yu dredged the earth, and the floods subsided, and then he established himself as leader of the first great dynasty of China.

Until now, this was a mythical origin story for the Chinese Empire. (Some versions include dragons.)

"He brings order out of chaos and he defines the land, separating what could become a civilized Chinese center from wild land of the peripheries," archaeologist David Cohen said in a press conference Wednesday.

On Thursday, Cohen and an interdisciplinary team of scientists presented the first definitive evidence — from the victims of a killer earthquake — that a catastrophic flood really did occur along the Yellow River about 4,100 years ago, overwhelming communities more than 1,200 miles downstream.

The collaboration pulled together geological evidence for floods with the archaeological remains of a prehistoric site downriver to pinpoint the severity flood and its date, which matches well with early Bronze Age China — and the story of Yu. Their findings will be published in the journal Science.

"This is the first time a flood of scale large enough to account for it has been found," Cohen said. "The outburst flood could've caused social disruptions lasting downstream for years."

From catastrophe to culture

Wu Qinglong Outburst floods happen when dams fail, releasing torrents of water into low-lying areas. In this case, an earthquake caused a landslide, damming part of the Yellow River in the Jishi Gorge. Less than a year later, the water level breached the top of dam, flooding the communities below and swelling the river to over 100 feet higher than its current height.

"To put that into perspective, that’s roughly equivalent to the largest flood ever measured on the Amazon River, the world's largest river," geologist Darryl Granger told the press. "It's among the largest known floods to have happened on earth during the past 10,000 years."

One of those communities below was a settlement that archaeologists call Lajia. When the earthquake hit, the cave-dwellings of Lajia collapsed, killing those inside. The flood then covered the remains, preserving the record for future archaeologists.

First, geologists identified the flood sediments and mapping their locations to describe the flood channel, then reconstructed the dimensions of the dam to gauge how intense the flooding would have to have been to break through the dam. They figured out the landslide dam must have been slightly smaller than the Hoover Dam.

The skeletons of the cave dwellers provided crucial data on timing, allowing the team to date the flood to the early Bronze Age. In particular, the skeletons of children buried in the quake were essential to the discovery.

"Because children grow so quickly, their bones give a very accurate and reliable age at the time of their death. The three skeletons we dated and two others all agree perfectly well, and they tell us that the flood happened at 1922, plus or minus about 28 years, BCE," Granger said. "So this coincides remarkably well with the major cultural transition in China."

The science behind the legend

Skeletons of the cave-dwellers at the Lajia site. Cai Linhai

This is the first scientific evidence of not only the Great Flood, but the existence of Yu and the Xia dynasty itself. The only records of the Xia and the Great Flood were written about 1,000 years after the events were supposed to have happened.

A compelling detail is that historical texts put Yu's efforts to stem the floodwaters in an area called "Jishi."

The dates for the flood places the start of the Xia dynasty later than previously thought, in 1900 BC, rather than 2000 BC or earlier, as some timelines suggest. This means the dynasty existed squarely in the early Bronze Age, rather than the late Stone Age as previously though.

The timing of the flood also marks the transition from the neolithic period to the early Bronze Age in China — a cultural shift with huge implications. About this time, urban areas and walled settlements appeared, including Erlitou, an archaeological site that has been linked to the Xia Dynasty (but has never been confirmed through archaeological evidence).

Xia's existence has been contentious among archaeologists. Without written records tied directly to the civilization, some of have said that the facts of the Xia have been inflated or outright fictionalized to shore up subsequent dynastic leaders and the "mandate of heaven" that allowed them to rule.

In an accompanying "Perspectives" paper in Science, geologist David Montgomery, who was not involved in the research, writes that the discovery is exciting not just for scientists and sinologists, but folklorists and historians all over the world.

Almost every culture, after all, has some version of a great flood story, from the Sumerian Gilgamesh and the biblical Noah to the legends of the Salish people of North America.

"How many other ancient stories of intriguing disasters might just have more than a grain of truth to them?" Montgomery asked.

If the legend is true — it seems very plausible now — it means that this flood gave rise to one of the world's oldest and most enduring civilizations, enhancing our understanding of how our catastrophe has shaped and guided human progress.