The earliest known domestic rice was cultivated in China as early as 9,400 years ago, at the beginning of the Holocene epoch, according to a new study. Carbon dating of rice fossils from Shangshan in the Lower Yangtze region shows domestication occurred there at least 9,400 years ago. Archaeologists have unearthed bits of rice from when it was first domesticated in China. The site of the first domestication of rice is a hotly contested issue, with several countries eager to lay claim. Several locations in China have been put forward, as have the Ganges valley in India, the southern slopes of the Himalayas, and various places in Southeast Asia. There is even evidence to suggest that wild rice may have originated in Australia.
Shangshan, in China’s Lower Yangtze region, has long been one of the strongest contenders: fossils uncovered there are some of the earliest evidence of rice grown by humans. Remnants of rice are identified through microscopic bodies of silica called phytoliths. However, the species of rice – whether wild or domesticated – isn’t always clear from these remains. Around 10,000 years ago, as the Pleistocene gave way to our current geological epoch, a group of hunter-gathers near China’s Yangtze River began changing their way of life when they remarkably started to grow rice. The grains, of course, were eaten long ago and the plant stalks have long been rotten, but one tiny part of rice remains even thousands of years later; phytoliths or hard, microscopic pieces of silica made by plant cells for self-defense. These fan-shaped phytoliths, found on rice leaves, don’t burn, digest, or decompose but carry specific patterns that suggest people in Shangshan were not just gathering rice, but actually cultivating it 10,000 years ago. The team then examined the morphological characteristics of the rice remnants, and confirmed that the species is closer to modern-day rice than wild rice. Their results, published in the Proceedings of the National Academy of Science, suggest the Shangshan fossils are indeed evidence of the earliest domesticated rice, dating back to 9,400 years ago.
Furthermore, a research team led by Xinxin Zuo, a geophysicist at the Chinese Academy of Sciences in Beijing verified the age of the phytoliths at Shangshan by comparing them with carbon dating on other materials from the same environment. It went through the tedious process of sifting the phytoliths from dirt, washing and sieving and heating until they ended up with a white powder of pure phytolith. They then used carbon-14 dating to pinpoint the age of phytoliths found at different depths in the excavation. To prove the reliability of dating phytoliths, they compared the ages to that of other material, like seeds and charcoal, found at the same depth. They found that phytoliths in modern rice have more than nine fish-scale decorations. The ancient phytoliths in Shangshan were a mix of different numbers of fish-scale decorations—as they got younger, the proportion with more than nine increased and more like modern rice. This is evidence of rice’s gradual domestication, a process that is “long and slow,” says Jianping Zhang, a geologist at the Chinese Academy of Sciences. Wild rice didn’t become modern rice overnight. “Wild rice usually grows in swampy conditions, so they get plenty of water. Domesticated rice leaves are erect and distant from water, and so the leaves need to curl repeatedly to hold water,” Zhang explained. The curling creates more fish-scale decorations. These microscopic fish-scale patterns tell the story of a rice plant that may have lived some 10,000 years ago in Shangshan.