HONG KONG (Reuters) - Chinese farmers cultivated rice along the eastern coast as far back as 7,700 years ago and used fire and flood control measures to manage their fields, researchers said, citing new evidence.

Farmers walk on rice terraces in southwest China's Guangxi Zhuang Autonomous Region, May 25, 2007. Chinese farmers cultivated rice along the eastern coast as far back as 7,700 years ago and used fire and flood control measures to manage their fields, researchers said, citing new evidence. REUTERS/Nir Elias

In a letter published in Nature late last week, geographers in Britain and China described how they found artifacts -- bone, bamboo and wooden tools used for foraging and cultivation -- and high concentrations of charcoal in Kuahuqiao, a freshwater marsh about 200 km southwest of Shanghai.

“About 7,700 years ago, people started to burn woody crops and there’s a very high concentration of charcoal there and a decline of woody tree pollen,” said Zong Yongqiang of Durham University in the United Kingdom.

“These two give us a very clear indication that people used fire to open the site for settlement and cultivation. It wasn’t just one burn but over several decades to maintain the ground for rice cultivation ... This could be the earliest paddy cultivation in the world,” Zong told Reuters by telephone.

“They used animal bones as spades, for example, the shoulder blades of pigs (which have a) triangular shape.”

Other archaeologists found wood pilings which they believe were used as supports in the marshy ground to erect platforms for huts for the farmers and their families.

These early farmers were also able to protect their paddy fields from floodwaters in the low-lying coastal area, at a time when they were constantly threatened by rising sea levels.

“When we look at the diatoms (species of green algae that thrive in sea water), salinity was kept very low in the background of rising sea levels. That gave us another suggestion that the humans somehow managed to have very primitive ways of blocking seawater during flooding,” Zong said.

But the area was suddenly abandoned about 7,500 years ago, again evident from diatoms dating from that time.

“You can see an abrupt rise in marine and brackish water diatoms, which means that up to a certain point, the people couldn’t maintain the paddy fields because sea water levels kept rising and they overwhelmed the sites,” Zong said.

“They abandoned the sites, which they occupied for 200 years, and moved on to other sites, with similar marshy conditions,” he said, referring to Hemudu, 120 km east of Kuahuqiao, or Majiabang, which lies in between Shanghai and Kuahuqiao.

Again, the researchers secured evidence showing paddy cultivation in Hemudu and Majiabang began about 7,000 years ago.

The researchers are now setting their sights on Taihu lake, which lies about 150 km north of Kuahuqiao.

“Between 6,000-4,000 years ago, the community was so vibrant, they had jade, ceramic ware and rice production was so high. Then 4,000 years ago, this community just disappeared,” Zong said.

“Is it because of the sea level rising, or climate cooling? Was weather so cold that their harvests were harmed?”