Climate change is one of the important factors that restrict the development of prehistoric culture. Recently, researcher Tan Liangcheng from Institute of Earth Environment, Chinese Academy of Sciences led the reconstruction of stalagmites paleoclimatic climate. He found that 4,300 years ago to 3,900 years ago, the precipitation in in central and southern my country increased, accompanied by the occurrence of multiple floods and floods, which aggravated the decline of Shijiahe culture . The same series of studies also found that around 4,000 years ago, extreme heavy rainfall events lasting for about 20 years in the context of long-term drought; 4,390 years ago to 3,800 years ago, heavy rainfall events were also recorded in the upper reaches of Hanjiang .
The climate change during this period is called the 4.2 Millennium Event in the climatology community. What are its manifestations in the world and other regions of my country? What impact has it had on prehistoric cultures everywhere? Dayu controls floods and Are these floods and disasters "treat"?
1 The rise and fall of ancient civilizations may be related to drought
is located near the north latitude of the earth, and is distributed from west to east from the Mesopotamia , Nile basin, Indus basin, and Yellow River basin, which are distributed from west to east, which are respectively bred by Mesopotamia , Ancient Egypt , ancient Indian and Chinese civilizations. However, only the Chinese civilization has lasted to this day and has been endless. The successive demise of the other three civilizations around 4,200 years was puzzled. It was not until the end of the 20th century that the archaeologist Harvey Wes took the lead in establishing a connection between its decline and climate change that the mystery gradually resolved.
Wes discovered that a drought 4,200 years ago caused the wind and sand to sweep the Mesopotamia , causing the soil to become extremely barren, making it difficult for even earthworms to survive. The Akkad Empire, which made a living by agriculture, was unable to make ends meet, and the population began to migrate, and eventually collapsed 4150 years ago. Other studies found that 4200 years ago, the precipitation in summer in East African Plateau was reduced, and Lake Tar, one of the Nile's water sources, could not provide enough water, causing the ancient Egyptian kingdom in the lower Nile to gradually decline; the same drought also spread to the Indus Valley, resulting in the sudden interruption of the Halapa culture.
This climate mutation event has attracted the attention of scholars around the world due to its close connection with cultural development, and localities around the world are rushing to carry out paleoclimate research. Scholars represented by Wes believe it is a global dry-cold climate event, and the International Stratum Commission also included this drought event in the geological year representative as the beginning of the Meghalaya period. However, is the 4.2 Millennium Event really a global event? Is it manifested as drought in various places? With the emergence of more and more high-precision and high-resolution paleoclimatic records, the negative sound is becoming stronger and stronger.
stalagmites
2 stalagmites provide high-precision paleoclimatic records
stalagmites are the "fourth pillar" for paleoclimatic and paleoclimatic reconstruction (the other three pillars are ice core , loess, and deep-sea sedimentation), and are also a rare carrier for obtaining high-precision and high-resolution paleoclimatic records.
In karst areas, after atmospheric precipitation reaches the surface, carbon dioxide produced by vegetation respiration, dolomite and other carbonate rocks are dissolved on the surface, dolomite and other carbonate rocks. After the solution enters the cave with the cracks, it is again precipitated due to the supersaturation of calcium carbonate , and it is deposited at the bottom of the cave to form stalagmites. Therefore, the chemical composition of stalagmites retains information such as atmospheric precipitation, temperature, atmospheric particulate matter and soil environment. Taking stalagmites carbon isotopes and trace elements as examples, the more precipitation, the more lush vegetation is, the more carbon dioxide is generated by respiration, and more lighter carbon isotopes are gathered in stalagmites. At the same time, the preferential deposition of carbonate is weakened, or the solution is more acidic, and more carbonate rocks are dissolved per unit time, resulting in a smaller proportion of trace elements/ calcium element ratio recorded in stalagmites.
Taking this study as an example, the team of researcher Tan Liangcheng collected a stalagmites in a cave in western Hunan and established a chronological ruler for stalagmites, and determined that it grew from 5667 to 3885 years ago, with most of the chronological errors less than 10 years.Through analysis, the precipitation changes from 5700 to 3900 years ago in central and southern my country were reconstructed, and it was found that 5700 to 4300 years ago, the precipitation in central and southern China gradually decreased; and then at the 4.2 millennium event (4300 to 3900 years ago), the precipitation increased, accompanied by the occurrence of multiple floods and disasters.
3 New research reveals that the paleoclimate wetness in the southern region
In the early stages of the study, records of loess and lakes from different regions of China showed that China was in a dry and cold climate 4,200 years ago. In recent years, researcher Tan Liangcheng and others conducted stalagmites on the western edge of the Loess Plateau and the Northeast, which also supported the arid climate in northern China 4,200 years ago. Zhejiang University Professor Yang Xiaoping and others believe that the degree of drought has even led to the desertification of Hunshandake in southeastern Inner Mongolia.
However, there are more and more doubts about the climate in southern China. At first, there were only sporadic research. For example, Wu Wenxiang and Liu Dongsheng Academician proposed in 2004 that China presents the climate mode of " flooding in the south and drought in the north". In 2018, Tan Liangcheng and others' research confirmed the climate pattern with high precipitation in central and southern China and low precipitation in the north 4,200 years ago; subsequently, Professor Zhang Haiwei and others' research in Jiangxi also verified this point. The dry-wet demarcation may be Qinling north- along the downstream of the Yangtze River . This study by Tan Liangcheng's team of researchers in western Hunan provides another evidence of the humid climate in central and southern China 4,200 years ago. However, in the future, more paleoclimatic records are needed in southern my country to have a clearer and more comprehensive understanding of China's spatial precipitation pattern.
It is worth mentioning that the humid climate in central and southern China revealed by Tan Liangcheng and others is no exception in the world. Some records of Mediterranean also show that rainfall increases during the 4.2 millennium event; some records such as North Atlantic north of and Rodriguez Island did not find obvious drought. This shows the complex manifestation of the 4.2 Millennium Event around the world and cannot be generalized.
4 4200 years ago floods and Dayu flood control
Although there is still controversy in the academic community about the humid and arid climate background in north and south China 4200 years ago, different geological records show that climate change 4200 years ago is not stable, and there have been many heavy rainfall events. In line with this, multiple ancient flood records left 4,200 years ago were found in the sedimentary sequences in many estuary areas, as well as the rise in Yunmengze Lake on the Jianghan Plain and the rise in sea level in the lower reaches of the Yangtze River.
Do these heavy rainfall/flood events conflict with the climate background of north and south China, especially the arid climate in the north? The answer is no. Tan Liangcheng and others introduced that the "dry" or "wet" of "wet in the south and dry in the north" refers to the overall and relatively long-term climate background, while heavy rainfall/flood events are climate change from the interdecadal to a shorter time scale. However, it is not yet certain whether the flood events in these two major basins occur simultaneously.
No matter what, these flood records inevitably make us connect it with the legend of Dayu's flood control. In a sense, they should be mutually verified. But with such a big flood, in an era of backward prehistoric technology, what kind of magical power does Dayu have to successfully control water?
The research of Tan Liangcheng and others in the Crow Cave in Gansu may be able to answer it for us. They used stalagmites oxygen isotopes in the crow's cave to reconstruct the rainfall changes in the Loess Plateau over the past 6,000 years, and found that around 4,000 years ago, there were extreme heavy rainfall events on the Loess Plateau that lasted for about 20 years, which may have caused a major flood in the Dayu era in the middle and lower reaches of the Yellow River. Since the chronological point of 4000±48 years ago is very consistent with the establishment time of the Xia Dynasty in 2070 BC, which was inferred by the Xia Dynasty in the Xia Dynasty in 2070 BC, the consistency between stalagmites records and archaeological and historical document records to a certain extent support the flood event and the authenticity of the Xia Dynasty in my country.
records show that the precipitation in the region began to decrease after that. Considering the low production technology level of prehistoric human society, Tan Liangcheng and others believe that the natural reduction in rainfall may also be one of the important reasons for Dayu's successful flood control.
Dayu’s flood control imagination
5 The decline of Neolithic culture is related to climate
Paleoclimate research shows that in the middle of the Holocene (8,000 years ago to more than 4,000 years ago), my country’s climate is suitable, providing extremely favorable conditions for the development of prehistoric culture. Neolithic cultures have taken root and sprouted in my country like mushrooms after a rain, and have continued to grow. 4500 years ago to 4200 years ago, northern China's cultures such as Taosi culture in Shanxi and Longshan culture in Shandong; southern cultures such as Shijiahe culture in the middle reaches of the Yangtze River, Liangzhu culture in the lower reaches of the Yangtze River, etc. are approaching the threshold of civilization. Among them, Liangzhu culture is the empirical evidence of China's 5,000-year-old civilization and has been recognized by the international community.
However, except for Taosi culture, other Neolithic cultures began to fall like stars 4,200 years ago. Such a synchronous decline and the decline and the three major ancient civilizations in the world are undeniable.
4200 years ago, my country had formed an agricultural model of "rice in the south and millet in the north". When rainfall in the north decreases, crop harvests decrease and population pressure is high, which leads to the collapse of northern culture. Although southern rice has a large demand for water sources, the precipitation in the southern region is already relatively high, and the river network is well developed, drought will not restrict the cultivation of southern rice. Therefore, the view that drought in southern China, which was proposed by some early studies, led to poor rice harvest and cultural decline, is untenable in a sense.
Research on the confusing of the cave by Tan Liangcheng and others, as well as the research on the Shennong Cave in Jiangxi, Zhang Haiwei and others, believe that the humid climate around 4,200 years ago and flood disasters caused a heavy blow to the Shijiahe culture and Liangzhu culture in the Yangtze River Basin, and this view has also received more and more support from people. This shows that in prehistoric times, drought was conducive to the development of the southern region to some extent, and the humid and rainy climate had a greater negative impact on the southern region.
Extended reading
Climate is not the only factor restricting the development of prehistoric culture
It should be noted that although climate change has played an important role in the process of human civilization, it is not the only decisive factor. Topography, war and conflicts often affect cultural development. As Tan Liangcheng's latest research believes that military conflicts and the combined effect of climate and landforms have led to the decline of Shijiahe culture.
5700 to 4300 years ago, with the reduction of rainfall, the settlement sites in the region gradually expanded and grew from the high terrain areas in the western region to low-lying and water-rich areas in the eastern region. Shijiahe City became the political and cultural center of the middle reaches of the Yangtze River during the same period. However, after 4,300 years ago, the climate in the region gradually became wet, and accompanied by multiple floods and disasters, it dealt a heavy blow to the Shijiahe cultural settlement in low-lying areas. At the same time, the military conflict between Shijiahe culture and Wangwan Phase III culture (Yufa Sanmiao) accelerated the demise of Shijiahe culture.
(Original title: What is the truth about Dayu's flood control? Restore the climate history of my country more than 4,200 years ago)
Source: Beijing Daily Author: Wang Tianli PhD, Institute of Earth Environment, Chinese Academy of Sciences,
Process Editor: U063
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