Shifting monsoon altered early cultures in China, study says

Related Articles

Related Articles

The annual summer monsoon that drops rain onto East Asia, an area with about a billion people, has shifted dramatically in the distant past, at times moving northward by as much as 400 kilometers and doubling rainfall in that northern reach. The monsoon’s changes over the past 10,000 years likely altered the course of early human cultures in China, say the authors of a new study.

Researchers from the Lamont-Doherty Earth Observatory and the Chinese Academy of Sciences in Xi’an studied ancient water levels for Lake Dali, a closed-basin lake in Inner Mongolia in the northeast of China. They found that the lake was six times larger and water levels were 60 meters higher than present during the early and middle Holocene–the period beginning about 11,700 years ago, and encompassing the development of human civilization.

“I think it is important to emphasize that these spatial fluctuations in the monsoon drive large changes in northern China,” said Yonaton Goldsmith, a graduate student at Lamont-Doherty Earth Observatory and lead author of the paper. “When the monsoon is strong, it shifts northward and northern China becomes green. When the monsoon is weak, the monsoon stays in the south and northern China dries out. Such large fluctuations must have altered the ecosystems in northern China dramatically.”

 

The study, appearing this week in the Proceedings of the National Academy of Sciences, also ties the shifting monsoon to changes in the earth’s orbit and other periodic changes in the climate system. The study should help scientists understand how the monsoon is affected by those natural cycles, and how a changing climate today might influence the monsoon in the future.

Goldsmith said it’s still unclear how the monsoon will react to global warming. One view is that the monsoon should grow stronger, but the area studied has been drying out over recent decades, he said, “so there is still a lot that needs to be done in that region before we can get definitive answers.”

Dali Lake is located near the northwestern limit of the East Asian monsoon, and so would reflect the changes brought about when the monsoon shifted north. The researchers studied outcrops of sediments left behind when the lake was far larger, and used those and other markers to construct a timeline of lake levels, and the fluctuation of rainfall over millennia.

They found that the lake reached peak levels around 123,000 years ago, again around 58,000 years ago, and once more between 11,000 and 5,500 years ago. They tie the periodic increases in rainfall to the range of the monsoon shifting north by as much as 400 kilometers. The lake record is “highly correlated” with measurements taken earlier from cave deposits in both northern and southern China.

Between 5,500 and 5,000 years ago, the monsoon weakened and rainfall over northern China decreased by 50 percent, the researchers found. They speculate that this drying triggered a major cultural transition in the region. As they describe it, two early Neolithic societies, the Hongshan culture in North China and the Yangshao culture in central China, collapsed around 5,000 years ago. In central China, the following period saw the rise of more stratified and socially and politically complex societies, including the Longshan culture. Previously unoccupied areas on the eastern margin of the Tibetan plateau were populated. Meanwhile, northeast China experienced a sharp population decline, represented by the Xiaoheyan culture.

“These findings show that climate change can have dramatic effects on human societies and highlight the necessity to understand the effect of global warming on rainfall patterns in China and all over the world,” the authors write.

Intense variations in rainfall may have played a role in the collapse of other civilizations. A study led by Lamont scientist Brendan Buckley, published several years ago, suggested that extended drought coupled with changes in the monsoon could have doomed Cambodia’s ancient Khmer civilization at Angkor nearly 600 years ago. Drought is thought to have played a role in the decline of the Classic Maya civilization, too, though in that case, another Lamont study suggests that the Maya themselves contributed to the drought by clearing forests for cities and crops.

THE EARTH INSTITUTE AT COLUMBIA UNIVERSITY

Download the HeritageDaily mobile application on iOS and Android

More on this topic

LATEST NEWS

Giant Sand Worm Discovery Proves Truth is Stranger Than Fiction

Simon Fraser University researchers have found evidence that large ambush-predatory worms--some as long as two metres--roamed the ocean floor near Taiwan over 20 million years ago.

Burial Practices Point to an Interconnected Early Medieval Europe

Early Medieval Europe is frequently viewed as a time of cultural stagnation, often given the misnomer of the 'Dark Ages'. However, analysis has revealed new ideas could spread rapidly as communities were interconnected, creating a surprisingly unified culture in Europe.

New Starfish-Like Fossil Reveals Evolution in Action

Researchers from the University of Cambridge have discovered a fossil of the earliest starfish-like animal, which helps us understand the origins of the nimble-armed creature.

Mars Crater Offers Window on Temperatures 3.5 Billion Years Ago

Once upon a time, seasons in Gale Crater probably felt something like those in Iceland. But nobody was there to bundle up more than 3 billion years ago.

Early Humans Used Chopping Tools to Break Animal Bones & Consume the Bone Marrow

Researchers from the Sonia and Marco Nadler Institute of Archaeology at Tel Aviv University unraveled the function of flint tools known as 'chopping tools', found at the prehistoric site of Revadim, east of Ashdod.

50 Million-Year-Old Fossil Assassin Bug Has Unusually Well-Preserved Genitalia

The fossilized insect is tiny and its genital capsule, called a pygophore, is roughly the length of a grain of rice.

Dinosaur-Era Sea Lizard Had Teeth Like a Shark

New study identifies a bizarre new species suggesting that giant marine lizards thrived before the asteroid wiped them out 66 million years ago.

The Iron Age Tribes of Britain

The British Iron Age is a conventional name to describe the independent Iron Age cultures that inhabited the mainland and smaller islands of present-day Britain.

Popular stories

The Iron Age Tribes of Britain

The British Iron Age is a conventional name to describe the independent Iron Age cultures that inhabited the mainland and smaller islands of present-day Britain.

The Roman Conquest of Wales

The conquest of Wales began in either AD 47 or 48, following the landing of Roman forces in Britannia sent by Emperor Claudius in AD 43.

Vallum Antonini – The Antonine Wall

The Antonine Wall (Vallum Antonini) was a defensive wall built by the Romans in present-day Scotland, that ran for 39 miles between the Firth of Forth, and the Firth of Clyde (west of Edinburgh along the central belt).

Vallum Aulium – Hadrian’s Wall

Hadrian’s Wall (Vallum Aulium) was a defensive fortification in Roman Britannia that ran 73 miles (116km) from Mais at the Solway Firth on the Irish Sea to the banks of the River Tyne at Segedunum at Wallsend in the North Sea.