Although scholars have come close to a consensus concerning the origins of rice in China, its subsequent spread outside of the center of domestication in the Yangtze Valley is still a matter of controversy. Scholars have generally agreed that the original domesticated plant for all varieties of rice is Oryza sativa japonica, domesticated from O. rufipogon in the lower Yangtze River Valley by Jomon culture hunter-gatherers approximately 9,000 to 10,000 years ago.
Recent research, reported in the journal Rice in December 2011, describes at least 11 separate routes for the spread of rice throughout Asia, Oceania, and Africa. At least twice, say scholars, a manipulation of japonica rice was required: in the Indian subcontinent about 2500 BC, and in West Africa between 1500 and 800 BC.
Possible Domestication
For quite some time, scholars have been divided about the presence of rice in India and Indonesia, where it came from and when it got there. Some scholars have argued that the rice was simply O. japonica, introduced straight from China; others have argued that the O. indica variety of rice is unrelated to japonica and was independently domesticated from Oryza nivara.
Most recently, as described in Rice, scholars suggest that Oryza indica is a hybrid between a fully domesticated Oryza japonica and a semi-domesticated or local wild version of Oryza nivara.
Unlike Oryza japonica, Oryza nivara can be exploited on a large scale without instituting cultivation or habitat change. The earliest type of rice agriculture used in the Ganges was likely dry cropping, with the plant's water needs provided by monsoonal rains and seasonal flood recession. The earliest irrigated paddy rice in the Ganges is at least the end of the second millennium BC and certainly by the beginning of the Iron Age.
The archaeological record suggests that Oryza japonica arrived in the Indus Valley at least as early as 2400-2200 BC, and became well-established in the Ganges River region beginning around 2000 BC. However, by at least 2500 BC, at the site of Senuwar, some rice cultivation, presumably of dryland Oryza nivara was underway. Additional evidence for the continuing interaction of China by 2000 BC with Northwest India and Pakistan comes from the appearance of other crop introductions from China, including peach, apricot, broomcorn millet, and Cannabis. Longshan type harvest knives were made and used in the Kashmir and Swat regions after 2000 BC.
Although Thailand certainly first received domesticated rice from China – archaeological data indicates that until about 300 BC, the dominant type was O. japonica – contact with India about 300 BC, led to the establishment of a rice regime dependent on wetland systems of agriculture, and using Oryza indica. Wetland rice – that is to say rice grown in flooded paddies – is an invention of Chinese farmers, and so its exploitation in India is of interest.
Paddies and rice
All species of wild rice are wetland species: however, the archaeological record implies that the original domestication of rice was to move it into a more or less dryland environment, planted along the edges of wetlands, and using natural flooding and annual rain patterns. Wet rice farming, that is to say, including the creation of rice paddies, was invented in China about 5000 BC, with the earliest evidence to date at Tianluoshan, where paddy fields have been identified and dated.
Paddy rice is more labor-intensive then dryland rice, and it requires an organized and stable ownership of land parcels. But it is far more productive than dryland rice, and by creating the stability of terracing and field construction, it reduces environmental damage. In addition, allowing the river to flood the paddies maintains the replacement of nutrients taken from the field by the crop.
Direct evidence for intensive wet rice agriculture, including field systems, comes from two sites in the lower Yangtze (Chuodun and Caoxieshan) both of which date to 4200-3800 BC, and one site (Chengtoushan) in the middle Yangtze at about 4500 BC.
Rice in Africa
A third domestication/hybridization appears to have happened during the African Iron Age in west Africa, by which Oryza sativa was crossed with O. barthii to produce Oryza glaberrima. The earliest ceramic impressions of rice grains date from between 1800 to 800 BC in the side of Ganjigana, in northeast Nigeria. documented domesticated O. glaberrima has first been identified at Jenne-Jeno in Mali, dated between 300 BC and 200 BC.
Sources
This article on the domestication of rice is a part of the About.com Guide to Plant Domestications, and part of the Dictionary of Archaeology.
- See the History of Rice Part 1, Rice Domestication in China
- See the complete bibliography
Primary Sources
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