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Stone Age paddy fields tended by the world's earliest known rice farmers have been uncovered in a swamp in China, scientists say.

The discovery shows rice growing began in the coastal wetlands of eastern China some 7,700 years ago, according to a new study.

A reconstructed hut at the ancient Chinese settlement of Hemdu may resemble the elevated structures used by the first known rice farmers some 7,700 years ago, scientists say.

A new study of artifacts and sediments found at Kuahuqiao, China, show that Stone Age farmers there used fire and even flood control to develop the earliest rice paddies ever found.

Evidence of prehistoric rice cultivation, including flood and fire control, was found by a team led by Cheng Zong of Britain's Durham University.

The team's research, which sheds new light on humans' critical transition from hunter-gathers to farmers, centers on the site of Kuahuqiao in Zhejiang province near present-day Hangzhou.

The research follows previous excavations at the site that revealed a Stone Age community of wooden dwellings perched on stilts over the marshy wetlands.

An 8,000-year-old dugout canoe, pottery made with wild rice as a bonding material, wood and bamboo tools, and the bones of dogs and pigs were also found.

Zong's team analyzed the sediments of the ancient swamp for signs of rice paddies.

The researchers found the land was deliberately managed for rice growing.

Fire was used to clear scrub, while flood-prevention measures helped keep brackish water from getting into the fields, the study suggests.

"The site provided us well-dated evidence for the earliest rice cultivation," Zong said.

Rising Seas

Kuahuqiao supported rice farming until around 7,550 years ago, when rising sea levels suddenly deluged the area, Zong said.

"Rice doesn't like saltwater," he said, noting that sea levels were rising at the time due to climate warming.

"We think [saltwater levels] must have been managed. Otherwise you would see a gradual rise in the brackish water influence," he said.

The water may have been held back by small earth dikes known as bunds, Zong said.

The team also detected increased levels of animal and human dung on the rice fields.

"Whether the dung was deliberately used as fertilizer, or whether it was just washed naturally into the paddy fields, it's very difficult to be certain," Zong said.

Rice fragments found in the swamp belonged to wild strains, the team found.

The discovery of unusually large rice pollen grains, however, may signal the beginnings of domesticated varieties, Zong said.

The team's findings are published in the latest issue of the journal Nature.

Other recent studies have dated the first fully domesticated rice in China to about 6,000 years ago.

Dorian Fuller of University College London, author of one such study, said the "evolution of rice as a domesticated crop was a long, drawn-out process which may have taken millennia."

The inhabitants of Kuahuqiao would have been "forager-cultivators," Fuller said.

"Rice cultivation isn't the only thing they do, and it's possibly not the main thing they do," he added.

"People who were using a wide range of other resources, including acorns and water chestnuts, started to manipulate marshland environments where rice was wild," Fuller added.

Who Farmed It First?

The new study provides the earliest known evidence of rice paddies, Fuller said, though other, less solid evidence points to rice farming elsewhere in China around the same period.

Wild rice grains from Stone Age sites along the middle Yangtze River have been dated to 6000 B.C., he noted.

"People were using rice earlier than this," he added.

He explained that rice farming likely evolved independently in different parts of Asia, such as along the Ganges River in India.

"It's very clear now from the genetics of modern rice that it has multiple origins from the wild gene pool right across southern China and northern and eastern India," Fuller said.

Gary Crawford, an anthropologist at the University of Toronto at Mississauga, said that the new study is "an important contribution to understanding agricultural origins in the rice regions of East Asia."

The study, he said, provides "a fascinating interpretation that rice cultivation was taking place in slightly brackish coastal wetlands that were regularly flooded."

It's hard to tell from the rice grains found whether the plants grown were wild or cultivated, he added, but "they are a long way outside the presumed geographic range of rice at the time."

The study team says the move toward rice farming by the Kuahuqiao people was likely spurred by the onset of warmer, wetter conditions ideally suited to growing the cereal plant.

The changing climate acted as a "critical environmental prompt to cultural change, permitting rice cultivation at this latitude," the team said.

 

 

英文原文版权归 NationalGeographic James Owen

图片版权归 Y.Q. Zong

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