Where does the rice we eat every day come from? Understanding the origins of rice in one article
Rice(Oryza sativa) can be said to be one of the crops most familiar to us Chinese. Its culinary uses were already covered by Species Calendar two years ago, which you can see here. What we want to understand today isthe origin of rice.
No rice, no meal. Image: magaret_1974 / pixabay
Rice sustains the largest population in the world, but where it originated is a very complex question. Since the early 20th century, whether rice originated in China or India has been hotly debated, going through several dramatic reversals, and to this day there is still no complete consensus. Over the past nearly hundred years, as research methods have deepened, although stage-by-stage conclusions have shifted back and forth, the picture of rice's origin has become increasingly clear.
Plump rice ears. Image: IRRI Images / Flickr
Before we introduce the latest progress of 2018, let us first review the past "battle situation" in this war over the place of origin.
The founding father of the field ignites the flames of war first
In the 19th century, there was a French botanist named Alphonse de Candolle, who in his book Origin of Cultivated Plants argued that rice originated in India, one reason being thatmany wild rices had been found in India. In the early 20th century, another Soviet scholar who studied the origins of cultivated crops, Vavilov, also believed that rice originated in India. With the arguments of these two masters, the idea that rice originated in India naturally became the mainstream view in academic circles at the time.
Swiss botanist Alphonse de Candolle: the first person to ignite the war over rice's origin. Image: wiki commons
By 1926, Ding Ying, the founder of rice research in China, also discovered wild rice in China. Two years later, he wrote A Study of the Names and Realities of Cereals, proposing that China was the original home of rice, and thus the "war" over rice's origin began. Ding Ying particularly emphasized that rice has two main cultivated variety groups: one isindica rice, withlong, slender grains that are not sticky when cooked[xiān]and generally prefer warmth,and the other isjaponica rice, withshort, stout grains that are somewhat sticky when cookedand are generally more cold-tolerant. The rice cultivated in India is mainly indica rice, but China has both indica and japonica rice, each with large numbers of varieties. This diversity strongly indicates that the original home of cultivated rice is in China.
Comparison of the grain shapes produced by japonica rice (left) and indica rice (right). Image: shutterstock.com
After 1949, Ding Ying's views gained a certain influence internationally. Although some Soviet scholars began to agree with the theory of rice's Chinese origin, the international mainstream still remained skeptical. It was also at this time that archaeology began to become an important means of determining rice's place of origin.
The battle unfolds in the archaeological community
From the 1960s to the 1980s, both China and India unearthed many prehistoric rice remains, and at the same time some ancient rice remains were also found in Thailand. For a time, rice's origin becamea "melee" among China, India, and Thailand。
After the initial frenzy, the archaeological community gradually calmed down and seriously re-examined the reliability of these archaeological evidences. In the end, scholars found that if evidence of the same standard is used for reference, then China's rice is clearly earlier than that of India and Thailand. Taking remains with complete grain morphology that can be conclusively identified as rice grains as an example, China's earliest isthe Hemudu site, dated to about 7,000 years ago, while India's is as late as 4,000 years ago. If less reliable evidence such as rice husks and phytoliths (a microscopic structure in rice cells) is also included, although India's history of rice cultivation can be extended to 4,500 years, some remains newly discovered in China after the 1980s can push China's history of rice cultivation back to 12,000 years ago!
Rice grains unearthed at the Hemudu site, some still very complete. Image: yongzhentang.com
Thus, by the end of the 20th century, the archaeological community had basically reached a consensus:rice was first domesticated in China and only later spread to India. However, the application of another new means of studying crop origins - molecular methods - brought this origin "war" back into a white-hot state.
The emerging field of molecular biology joins the battle
Some molecular biologists believe thatrice is not a single-origincrop; although japonica rice originated in China, indica rice originated in India, and the two were independently domesticated from corresponding wild rices. In the early 21st century, this view once gained the upper hand. However, scholars advocating a single origin of rice did not yield either. During rice's domestication, some traits favorable for harvest -non-shattering grains, upright rice stalks, and so on - were intentionally selected by early humans. These scholars found that the gene sequences determining certain domestication traits are almost identical in indica and japonica rice, which strongly suggests that rice was domesticated only once.
Upright growth and non-shattering seeds made rice a successful crop. Image: trivedieffect.com
In 2011 and 2012, two research groups successively carried out larger-scale and more rigorous DNA studies, and finally concluded that rice first originated in southern China, that japonica rice appeared first, and that later during its spread to India it acquired indica-type genes from wild rice and only then gradually transformed into indica rice. In this way, on this molecular battlefield, China also temporarily won.
The "war" is not completely over yet. On April 25, 2018, a latest study jointly published in Nature by 72 authors from 16 institutions, including the Institute of Crop Sciences of the Chinese Academy of Agricultural Sciences and the International Rice Research Institute, showed that the origin of indica rice is more complex than previously determined. This time, using newer sequencing technology, they determined the whole genomes of 3,024 cultivated rice samples in total, then processed and compared 3,010 high-quality data sets with computer programs, and specifically paid attention during the process to 9 key gene sequences that were selected during rice's domestication.
The results were astonishing: among 1,789 indica rice samples, only 1 specimen had all 9 of these gene sequences completely identical to japonica rice, while other indica rices had at least 1 gene sequence very different from japonica rice,which indicates that it has an origin independent of japonica rice。
Faced with such results, the researchers proposed a more reasonable theory: rice was indeed independently domesticated in China and India respectively,China domesticated japonica rice, and India domesticated indica rice. Later, Chinese japonica rice spread to India and over a long period hybridized with local primitive indica rice, eventually forming today's modern indica rice varieties that are mixed to varying degrees with japonica genes. So the latest "battle situation" in the war over rice's origin is - India has once again pulled back a point.
Of course, we must not forget that the reason molecular biologists have been able to keep deepening their work on this question is thanks to Asian rice farmers preservinghundreds of thousands of landraces. This enormous diversity not only provides diners with many choices, but also provides a large amount of material for rice breeding, and moreover preserves rich information about cultivation history, ultimately allowing scientists to glimpse the secrets of rice's origin.
Various kinds of rice. Image: gov.sg
If rice were like bananas, with only a few commercial varieties widely cultivated while many landraces were pushed out and nearly wiped out, then what humanity would forever lose would not only be thosediverse flavors and traits, but also a crop domestication history that fully records the wisdom of our ancestors.
The same principle, why should it not also apply to the diversity of human culture?
This article is the 226th article of the 4th year of Species Calendar, from Species Calendar author @Liu Su.
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