On May 24th, about 120 kilometers from Hangzhou in Pujiang County, Zhejiang Province, under the blue sky and white clouds, surrounded by rice fields, an important discovery was made at the Shangshan site.
Researchers from the Institute of Geology and Geophysics of the Chinese Academy of Sciences, including Lü Houyuan and Zhang Jianping, in collaboration with the Zhejiang Provincial Institute of Cultural Relics and Archaeology, Linyi University, and 13 other domestic and international institutions, used rice "fingerprints" - such as the number of fish scale patterns in phytolith microfossils - to unlock the continuous 100,000-year evolutionary history of rice from wild to domesticated. The study further confirmed that China is the birthplace of world rice, with the Shangshan culture from about 10,000 years ago playing a significant role. The related research was published in "Science."
"The evidence is conclusive, and the conclusion is highly innovative," said an international reviewer, praising the study for delving deep into the long evolutionary history of rice in China, changing people's understanding of the global agricultural origins, and providing the most comprehensive evidence to date for the origin of East Asian rice, with significant academic value.
"This is a scientific breakthrough and a civilizational revelation," said Di Qingyun, Director of the Institute of Geology and Geophysics, noting that the origins of wheat and rice are important milestones in human development history. The evidence of rice domestication at the Shangshan cultural site indicates that the origins of rice agriculture in East Asia and wheat agriculture in the Mesopotamian region were synchronous in time, significantly deepening the understanding of the global agricultural origins and making an important contribution to enhancing cultural confidence.
The Shangshan Site. Zhang Guoping provides images at the Shangshan Site.
Missing Evidence Chain
Rice is the staple food for half of the global population. But when and where did humans first plant and eat rice, marking the beginning of agriculture?
For over a century, this question has been a topic of debate. Theories such as the origin in India, Southeast Asia, Assam, and Yunnan have been proposed, leading to various speculations.
It wasn't until the 1970s when the discovery of rice archaeological evidence at sites like Hemudu in Yuyao, Zhejiang, Shangshan in Pujiang, and many other sites in the middle and lower reaches of the Yangtze River, that the international academic community began to recognize the possibility that the middle and lower reaches of the Yangtze River could be one of the important origins of rice in the world.
"However, until the early 21st century, the accepted origin of agriculture thousands of years ago was in Central and South America and West Asia, excluding East Asia," said Lv Houyuan, the first co-corresponding author of the paper, to China Science Daily.
The key issue lies in the lack of fossil evidence.
The traditional belief is that during the last glacial period, from 26,500 to 19,000 years ago, the lower and middle reaches of the Yangtze River did not have wild rice due to the lower temperatures. "Without wild rice, where did the domestication come from?" Lv Houyuan said. "Due to the humid climate in East Asia, organic matter buried in the soil after plant death easily decomposes, making it difficult to identify and provide evidence for the transition from wild rice to cultivated rice before 8,000 to 10,000 years ago."
So, are there identifiable indicators for rice that can be preserved long-term? Can evidence of wild rice during the last glacial period in the Yangtze River Basin be found? Can the process of human domestication of wild rice be revealed along with its potential mechanisms?
For over 20 years, Lv Houyuan and his team have been attempting to answer these questions using phytolith microfossils. "Phytoliths are silica particles filled in the cell tissues of higher plants. They are abundant and widely distributed, with tens of thousands of particles produced in one gram of leaf. Silica, like glass, can be preserved for a long time. Whether it is consumed by animals and excreted or burned in a fire, it can settle in the soil," explained Zhang Jianping, the first co-corresponding author of the paper, to China Science Daily.
More importantly, Lv Houyuan stated that like human "fingerprints," different plants' phytoliths have distinct morphological characteristics. For example, rice phytoliths have fan-shaped scales, bamboo has elongated saddles, and reeds have shield shapes.
Since the late 1980s, Lv Houyuan and his team have been studying phytoliths, standing out in China. They have traveled across the country, collecting topsoil samples from different climatic zones, analyzing the characteristics and distribution patterns of phytolith combinations in different vegetation zones, collecting thousands of plant samples, identifying them with the help of botanists, conducting phytolith analysis, creating a set of sketches of modern phytoliths, publishing a monograph on phytolith research, producing many sets of microscope slides, and attracting many domestic and foreign students to study every year.
This technique has shown remarkable achievements in archaeological work at various sites in China, such as identifying the "noodles" at the Lajia site in Qinghai as made from broomcorn millet and the plant remains at the Cishan site in Wu'an, Hebei as millet. This crop phytolith identification method has been included in textbooks at many universities in Europe and America.
However, due to the similarity between the phytoliths of wild and cultivated rice, identifying their evolutionary differences has proven to be extremely challenging.
The Zhejiang Xiatang Site: Archaeologists Listening to a Lecture
Zhejiang Xiatang Site, with Lv Houyuan (far right), listening to an archaeologist explaining the profile. The Shangshan culture is distributed in Zhejiang Province, and the Xiatang Site belongs to the Shangshan culture. Geological map provided by the Institute of Geology.
Establishing a "New Standard"
As early as 1998, Lv Houyuan discovered phytoliths of rice plants in layers dating back over 13,000 years while analyzing samples from the East China Sea continental shelf drilling. Based on the analysis of limited modern wild rice and domesticated rice samples at that time, he found that the "fish scale pattern" in domesticated rice phytoliths is usually equal to or greater than 9, while in wild rice, it is mostly less than 9. However, the technology and limited fossil quantity at that time made it difficult to answer when wild rice began to be domesticated.
In 2017, Lv Houyuan and his students used a method to determine the number of fish scale patterns in phytoliths and found that the domestication of rice at the Shangshan Site could be traced back to 9,400 years ago. They believed that crop domestication is a lengthy process and there should be earlier records of the transition from wild to domesticated rice.
How to find evidence of earlier wild rice, distinguish between wild and domesticated rice, and establish an internationally recognized set of criteria?
"We put a lot of effort into answering this question, requiring collaboration with many units to obtain samples of wild rice. In the 'Carbon Special Project' of the Chinese Academy of Sciences that I was in charge of, teams of botanical experts from Wuhan Botanical Garden and other institutions provided rare opportunities to obtain samples," said Lv Houyuan.
The research team not only collected soil from different geological layers in the field, brought them to the laboratory for identification by separating phytoliths using chemical solutions, but also collected many present-day wild rice plants and soil from places like Hainan and Jiangxi for analysis. They transformed into "farmers," cultivated wild rice in greenhouses, eliminated domestication genes, identified each leaf one by one, and obtained a large amount of reproducible data.
Based on this, they established a set of quantitative standards: if the proportion of fan-shaped phytoliths with fish scale patterns greater than or equal to 9 reaches 40%, it is considered domesticated rice; otherwise, it is wild rice.
The research team further explained the reasons for the correlation between the number of fish scale patterns and the degree of rice domestication. Wild rice grows in water year-round, while domesticated rice requires periodic drainage. Therefore, the curling of rice leaves is an agronomic trait selected during human breeding. As the drought increases, rice leaves can repeatedly lose water and expand, leading to an increase in fish scale patterns.
To ensure the accuracy of dating, the dating of this study involved four laboratories from both domestic and international sources for mutual verification. "Optically stimulated luminescence dating mainly determines the age of sediment burial, using methods such as small chips and single-grain analysis, combined with chronological models to address stratigraphic disturbances. Combined with phytolith carbon-14 dating, these two dating methods can support each other to prove the reliability of the age," explained Yu Lupeng, co-corresponding author of the paper and professor at Linyi University in Shandong.
A series of interdisciplinary studies indicate that the Shangshan cultural site records the continuous process of East Asian rice from wild to domesticated. Wild rice was already growing here around 100,000 years ago, and around 24,000 years ago, during a cold climate period, it began to be utilized as a resource by humans. Cultivation of wild rice before domestication started around 13,000 years ago, and finally achieved domestication around 11,000 years ago, marking the origin of rice agriculture in East Asia.
Silica bodies of rice husks found at the Shangshan cultural site (the first three rows are fan-shaped silica bodies with different numbers of fish scale patterns, and the last row is rice husk silica bodies). Image provided by the Institute of Geology, Chinese Academy of Sciences.
It's like "opening blind boxes."
"The most important core of the Shangshan culture's application for World Heritage status is the origin of rice cultivation. New research provides strong support and key scientific evidence for the Shangshan culture as the birthplace of rice agriculture, which will help advance the local application for World Heritage status," said Jiang Leping, co-corresponding author of the paper and researcher at the Zhejiang Provincial Institute of Cultural Relics and Archaeology.
International reviewers believe that the origin of rice agriculture in East Asia's Shangshan culture, which began around 11,000 years ago, almost synchronizes with the development, utilization, and domestication of wheat and barley in West Asia. This synchronization implies that global climate change, landscape changes, as well as cultural exchange and inheritance, played important roles in the origin of crops.
Since starting his graduate studies at the Institute of Geology, Chinese Academy of Sciences in 2005, Zhang Jianping has been conducting research on silica bodies. Speaking about the ups and downs of research, he said, "The hardships of fieldwork are nothing compared to the anxiety of waiting for feedback on paper revisions, fearing that any detail might affect the publication of the article."
Over the course of two years, Zhang Jianping and his research team have been supplementing their silica body research data based on the reviewers' feedback. He feels that doing data research is like "opening blind boxes." Until all the data is completed and a complete picture is formed, the final outcome is completely unclear. "Sometimes the 'blind box' result turns out to be particularly good, exactly as expected, and can be quickly written up for publication. But if it's different from what was anticipated, we have to change our approach and conduct extensive analysis on the samples again. Until the very last moment of publication, our emotions are tormented," he said.
However, Zhang Jianping admitted that the sweetest moment is when the results are accepted. "Being recognized by international experts makes me feel that my work is worthwhile, that I have done something meaningful."
New research plans are in the works, as Lv Houyuan mentioned that there are still many mysteries to be answered regarding the domestication and origin of rice. For example, what genes control the variation of fish scale patterns in rice? How did perennial wild rice transform into annual wild rice that reproduces through seeds? Was the origin of rice a single event or multiple events? Was it a single-point domestication or multiple-point domestication? Was the domestication process rapid or did it span over long periods? He hopes to further conduct interdisciplinary research to explore the geological relationships between the Shangshan culture and other regions such as the Xianrendong site in Jiangxi and the Diaotonghuan site.
Shangshan Site Park. Photo provided by Zhang Guoping at the Shangshan Site Center.
Research team at Shangshan site (third from the left is Zhang Jianping, fourth from the left is Lv Houyuan). Image provided by Institute of Geology, Chinese Academy of Sciences.
Wild rice in Jiangxi. Geological Earth Supply Map
In the wild rice fields of Jiangxi, Lü Houyuan conducted experiments on harvesting wild rice using the unique large-mouthed basin model of the Shangshan culture. Image provided by the Institute of Geology, Chinese Academy of Sciences.
The research team at the Jingtoushan site in Zhejiang is using geophysical exploration methods (such as electrical and magnetic methods) to investigate the relationship between underground archaeological cultural layers and natural strata. They took a temporary break in the shed due to a sudden heavy rain (the person on the far right is Lü Houyuan). Geological Earth map provided by the Institute of Geology.
Related paper information: Link to the paper
