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China science

Where did that rice in your bowl originally come from?

Scientists find more evidence that staple food was first grown in China’s Zhejiang province

PUBLISHED : Tuesday, 30 May, 2017, 7:00am
UPDATED : Monday, 12 June, 2017, 12:53pm

A new Chinese study has added weight to Zhejiang province’s claim to be the place where rice was first domesticated.

Many places have claimed that honour in years of heated debate, including the Korean Peninsula, Japan, China, India and Cape York in Australia, but archaeological and genetic evidence unearthed during decades of research pointed to South China as the site of the key grain’s first cultivation.

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But precisely where in South China? The provinces of Zhejiang, Jiangxi, Hunan and Guangdong all claimed to be the birthplace.

In an article published in PNAS, the official journal of the prestigious National Academy of Sciences in the United States today, a team of mainland Chinese researchers give further credence to suggestions the earliest domestication of rice might have occurred at an archaeological site, Shangshan, on the lower reaches of the Yangtze River in Zhejiang around 10,000 years ago.

Carbon-dating of trace elements in fossil remains identified domesticated rice at least 9,400 years old.

“We have a high confidence it is not wild rice,” said Professor Lu Houyuan, a researcher with the Chinese Academy of Sciences’ Institute of Geology and Geophysics in Beijing and a lead scientist in the study. “It is not the same as rice today, either. It’s a half-domestic species.”

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What made the discovery different from findings elsewhere was that the researchers not only discovered rice remains in Shangshan, but also some of China’s earliest villages.

Another author of the study, Professor Jiang Leping from Zhejiang’s Institute of Cultural Relics and Archaeology, said 18 prehistoric settlements, each covering an area of between three and five hectares, had been discovered.

The earliest rice farmers were likely to have lived in houses, he said.

“We found perfectly aligned holes for pillars, similar to those used by sophisticated, multi-storey wood buildings in later ages,” Jiang said.

They also discovered what appeared to be agricultural tools, with unique marks on the sharp edges of some stone tools likely to have been caused by cutting through plants similar to rice stalks, suggesting use in harvesting.

What impressed Jiang most, though, were the mortars and pestles.

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“We have discovered quite a few sets; the mortars were up to 70cm wide, quite large,” Jiang said. “They were likely used to grind and separate the rice grain from the husk.”

He said Shangshan represented an early but complex civilization that was even aware of waste recycling. Instead of dumping the rice husks, for instance, the early farmers mixed them into clay to improve the physical strength and durability of ceramics.

“We believe each of these villages was surrounded by rice paddies,” Jiang said. “We will start a search to see if there is any sign of an early irrigation system.”

However, Professor Wang Zixuan, from the Chinese Academy of Sciences’ Institute of Plant Physiology and Ecology in Shanghai, said genetic evidence suggested rice was first domesticated in the Pearl River Delta.

He took part in a large-scale research project, the results of which were published in the journal Nature in 2012, that used genome sequencing technology to show that cultivated rice originated in a single location.

Wang and his colleagues compared the genetic variation between domestic and wild rice in different regions. The molecular analysis enabled researchers to trace a species’ evolution and pinpoint where it first emerged.

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“They could spread,” Wang said. “It is likely that the early farmers along the Pearl River took the rice seeds up north to the Yangtze during migration.”

Scientists have determined the origin of every other main agricultural plant. Millet, for instance, was first planted in North China; wheat in the Fertile Crescent of the Middle East; and maize, or corn, in southern Mexico. But rice has proved more difficult to pin down, due to the scarcity of remains. Rice is difficult to preserve because it grows in areas with high humidity and the acidic soil in rice paddies is not fossil-friendly.

The latest study focused on phytoliths – microscopic particles of silica formed in plant cells. Different plant species produce different phytolith patterns, which can be preserved in the environment for a long period. Domesticated rice contains a much higher proportion of fish-scale-shaped phytoliths than its wild cousins, which helped the scientists date samples and detect signs of selective breeding of what is now the world’s most widely consumed staple food.

“Tracing the origin of rice helps us understand what happened at the dawn of agriculture, one of the most important chapters in human history,” Lu said.