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India’s rice history may not have had anything to do with China

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At a lake called Lahuradewa in the Gangetic plain, three Lucknow researchers have found evidence of independent domestication of rice in India that predates China by 800 years.

Bengaluru: Indian paleo scientists have discovered in a lake called Lahuradewa in Uttar Pradesh, evidence of independent domestication of rice pre-dating established Chinese origins by 800 years. Existing theories state that Chinese first domesticated, and then spread rice to the rest of the world.

Authored by three researchers — Biswajeet Thankur, Anju Saxena, and Inderbir Singh, from Birbal Sahni Institute of Palaeosciences (BSIP), Lucknow — the new paper was published in Current Science.  earlier this year. BSIP is one of the country’s leading institutes of paleoscience — the branch of science studying pre-historic life, ecosystems, evolution, and other sciences — and was established in 1946 by the famed botanist Birbal Sahni, ‘Father of Dendrology’. It holds some of the country’s most advanced equipment for studying paleosystems and climatology.

The rice narrative

Origin of rice domestication has been a subject of much debate among those who study crop history and anthropology. Every study that establishes a date has been replaced by more advanced research with newer dates, going back and forth.

A 2012 study claimed that, rice was first cultivated in Pearl River valley in South China. Previous theories contradicted this only slightly; it was believed that rice originated in the Yangtze River valley. In fact, even South Korea claimed rice had been domesticated there much earlier than in China, but their studies were quickly discredited. Latest studies from 2016 dated rice fields back to China’s Yangtze valley 8,400 years ago.

Thakur’s paper dates cultivation in India to 9,250 years ago.

“We have previously had the same results using evidence from phytoliths (microscopic structures made of silica and produced by plants within their body which survive long after the plant dies). This paper confirms the date firmly,” explained Thakur. His team is working on the climate and environment dating to about 11,000 years ago, when human settlements began. “We aim to find out if Indian settlements occurred as early as others around the world,” he said. “And if settlers migrated into India from outside.”

How evidence was collected

To study the origin of rice cultivation, traditionally, phytoliths have been used for evidence. But these days, we have stronger, more advanced evidence in the form of ‘diatoms’. These are microorganisms that are present all over the world, producing over 20% of the world’s oxygen. When present in rice cultivated lands, they carry with them a unique signature. As paddy fields change seasonally, the diatoms that thrive in water abundance show signs of fluctuating water levels.

Diatoms primarily live in water bodies, and are classified into four types: planktic (free-floating in lake water), benthic (growing on sediment surfaces), paddy field (water-logged rice fields), and anthropogenic (water bodies with high pollution). The amount diatoms settled in lake beds over centuries vary in layers depending on lake conditions. If a lake expands, there is a larger number of planktic diatoms. If it shrinks, benthic population goes up. If there are rice fields around, paddy-field diatoms get washed into a lake in large numbers. And of course, if human-made pollution levels go up, the anthropogenic diatoms thrive.

The Lahuradewa lake, like many of the lakes in the Gangetic plain is very shallow, only a few metres deep and having flat, extensive lake margins that are used even today for agriculture. During the monsoons, when the lake expands, its water-logged margins are used for paddy cultivation. The rice is then harvested in October when the lake shrinks again. During any flooding event, all the evidence of rice cultivation such as diatoms, phytoliths, microcharcoal from grass, and some pollen get washed into the deeper parts of the lake, where they settle at the bottom.

Indian Gangetic settlements

The team used 28 different core samples from the lake bed for their observations. They noticed that from 10,600 to 9,900 years ago, the lake was shallow before it expanded until 7,000 years ago. In the meanwhile, at about 9,250 years ago, paddy field diatoms started showing up in large quantities, while anthropogenic ones turned up only a thousand years later.

This indicates that there was initially no pollution caused by settlements practicing established farming, such as carbon dioxide from cows, as it would have been had the practice come from China. Indian settlers had just been attempting to sporadically domesticate rice at this point, independently but in parallel with China.

Their study’s site was the Gangetic plains, which has evolved over time, thanks to river flow, tectonic activity, and climate change. The region is also a hot bed for studying ancient vegetation as fertile river banks are where the humans first settled across the world. The Lahuradewa lake is adjacent to the Lahuradewa excavation site where human settlement and early farming practices are being studied.

“Understanding such historical data helps us deduce what human response to sustainable conditions versus stressful ones were,” said Thakur. “We can then better model both future climate as well as human needs and responses to such changes.”

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