The sudden collapse of the last Neolithic culture of the lower reaches of the Yangtze River (eastern China), which occurred approximately 4,300 years ago, finally has an explanation.
This prehistoric civilization, known above all for the settlement of Liangzhu, has not left any evidence of a gradual decline or a warlike conflict that destroyed it, but a speleological analysis has allowed a group of researchers to discover what left that ancient town in ruins .
The Chinese geologist Haiwei Zhang brought several stalagmite samples of two caves which are to the southwest of the settlement that was being excavated, called Shennong and Jiulong.
💡#FunFactsAboutJiangxi: Although the temperature continues to drop, the Shennong Palace or Shennong Gong is still warm as spring! The underground karst cave has a permanent indoor temperature of 21℃ throughout the year. pic.twitter.com/zGMt5pzFzw
— Discover Jiangxi (@BeautyJiangxi) November 11, 2021
Both caves “had been quite explored over the years,” commented the scientist in a statement from the University of Innsbruck (Austria), which participated in the research. “They are located in the same monsoon affected area of Southeast Asia that the Yangtze Delta and its stalagmites provide an accurate idea of the time of the collapse of the Liangzhu culture, “he said.
Isotopic analysis of stalagmites revealed that more than 4,300 years ago (between 2324 and 2303 BC) there was a period of extremely high rainfall. The very fact of high humidity was established in Innsbruck by carbon isotope records, while the exact dating was made later by measurements of the combination of uranium and thorium at the University of Xi’an Jiaotong (China). Haiwei describes the result of applying this method as “astonishingly accurate in light of the time dimension”, since its margin of error is within the 30 years.
A thin layer of clay in the preserved ruins also points to a possible connection between the demise of advanced civilization and the floods of the Yangtze River or the swelling of the sea, according to Christoph Spötl, co-author of the study about it, published last week in the journal Science Advances.
The change that put an end to the ancient agricultural culture
5,300 years ago the archaeological culture of Liangzhu was already thriving and, at the time of its disappearance, it was almost a thousand years old. In the history of human civilization, it is one of the first examples of highly developed communities, based on a water infrastructure.
The walled settlement had a complex system of navigable canals, dams and water reservoirs, which allowed the population to cultivate large agricultural areas throughout the year. However, metals were not yet known to that culture and, therefore, it is part of the last of the late Neolithic.
The study points to excessive monsoon rains as the likely cause of an overflow of the Yangtze River of such magnitude that dams and canals could not withstand it, the city of Liangzhu was flooded and its population was forced to flee. Since then, very humid climatic conditions persisted for another 300 years, show geologists from the data collected in the caves.
In the context of global climate change, the phenomenon would be related to an increasing frequency, during that time, of the well-known El Niño / Southern Oscillation weather pattern, which scientists associate with the weakened summer insolation in the northern hemisphere.
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