The archaeological site of Yangzhou City is located in the Yangtze River Delta, about 160 km southwest of Shanghai. A sophisticated culture blossomed here about 5,300 years ago, thanks to the engineering advancements in large-scale hydraulic structures.
The walled city had a complex system of navigable canals, dams, and reservoirs. This system made it possible to cultivate very large agricultural areas all year round. It is one of the first examples of a highly developed community based on water infrastructure in the history of human civilization.
And they did it all without metal.
This long-undiscovered archaeological site is now considered a well-preserved record of more than 5,000 years of Chinese civilization and was designated a UNESCO World Heritage Site in 2019. But the city’s advanced civilization came to an abrupt end.
“Thin layers of clay were found in the preserved remains, suggesting a possible connection between the decline of advanced civilizations and the Yangtze River or East China Sea floods. A war-like conflict,” explains Christoph Spötl of the University of Innsbruck.
The water droplets in Shennong Cave (pictured) and Kowloon Cave provide an accurate glimpse into the period when the Liangzhu culture collapsed about 4,300 years ago. Credit: Zhang Haiwei
Dripstone saves the answer
Sediments such as caves and trickles are one of the most important climate archives in existence. This allows us to reconstruct the climatic conditions above the caves up to hundreds of thousands of years in the past. Because it is not yet clear what caused the sudden collapse of the Liangzhu culture, the research team looked to suitable archives to investigate possible climatic causes of this collapse.
Haiwei Zhang, a geologist at Xi’an Jiaotong University, collected stalagmite samples from two caves, Shennong and Jiulong, located southwest of the excavation site.
Data from the stalagmites show that there was a period of extremely high precipitation between 4345 and 4324. Evidence for this was provided by isotopic records of carbon measured at the University of Innsbruck. The exact date was determined through uranium-thorium analysis at Xi’an Jiaotong University, with an accuracy of ±30 years.
Heavy monsoon rains caused severe flooding in the Yangtze River and its tributaries, so much so that even elaborate dams and canals could no longer hold such massive amounts of water, destroying Yangzhou and forcing people to flee. As geologists show from cave data, very wet climate conditions continued intermittently for the next 300 years.
Citation: Haiwei Zhang, Hai Cheng, Ashish Sinha, Christoph Spötl, Yanjun Cai et al. Collapse of Yangzhou and other lower Yangtze Neolithic cultures due to climate change. science. advanced2021 DOI: 10.1126/sciadv.abi9275
