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First Ancient Cultivated Rice Discovered in Central Asia

The origin, spread, evolution, and ecological adaptation of cultivated rice is still one of the most important issues thatcurrently concern global archaeologists, biologists, and agricultural scientists

by Science China Press
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Satellite imagery of Khalchayan and surface remains within the site.
Chen Guanhan and Zhou Xinying, IVPP, ©Science China Press

Rice has always been the most important food in Asia and the world. About half of the population on earth use rice as their main food source. The origin, spread, evolution, and ecological adaptation of cultivated rice is still one of the most important issues that currently concern global archaeologists, biologists, and agricultural scientists.

In recent years, archaeobotany and molecular biology studies have shown the originally cultivated rice was domesticated into japonica rice (Oryza sativa japonica) in the lower Yangtze region, China, 10,000 years ago, then spread to Japan, South-, and Southeast Asia. About 5,000-4,000 years ago, the cultivated japonica rice spread to South Asia, hybridized with the native wild rice, gradually formed indica rice (Oryza sativa indica) and became the main crop in South Asia today.

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However, in recent years, research on the origin and spread of rice have mainly focused on East Asia, Southeast Asia, and South Asia. At present, we still know very little about when and how rice spread into West Asia, Europe, and Africa. The Central Asia region, as an important node in the ancient Silk Road cannot be ignored, because it is the "crossroad" of world civilization. Therefore, studying the time and location of rice emergence in Central Asia can help gain insight into the spread of rice agriculture and make an important contribution to early crop globalization research.

Recently, Li Xiaoqiang's research group in the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (IVPP, CAS), and other researchers in College of Cultural Heritage, Northwest University, China, Institute of Archaeology, Uzbekistan Academy of Sciences reported their latest research about the agricultural remains in Khalchayan site, Uzbekistan, which was published in Science China: Earth Science. Researchers investigated 11 sites on the northern bank of the Amu Darya from the Bronze Age to Arabian period and found carbonized rice remains at the Kalchayan site. With archaeobotany, chronology methods, and other local archaeological records, researchers provide new physical evidence for the spread of rice to western Asia and the exchange of eastern and western civilizations along the ancient Silk Road.

Khalchayan site is a city site in southeastern Uzbekistan. Researchers use a flotation method to obtain large amounts of botanical materials at a cultural layer in the southwest part of the site. The AMS 14C dating results showed that the age of the rice remains in the site are 1714-1756 cal. B.P.—the Kushan period. In addition to the rice remains, carbonized wheat, two-row barley, pea, millet, grapes, flax, and other crops were recovered at the site. These crops include both West Asian and East Asian origins, which illustrates a diverse and complex oasis farming system. Because rice cultivation requires a lot more heat and water than wheat and millet, this made it difficult to cultivate in arid regions in early times. But, combining the carbonized rice remains with the records of the irrigation systems existing in other local oases agricultural archeological sites during the Kushan period, researchers believe it is possible that rice cultivation occurred locally during that time.

Morphological studies show that the carbonized rice remains are japonica rice, and their morphology is similar to the remains found in some sites in southern China and northwestern India during the same period. That indicates the possibility that rice in Central Asia was spread from South Asia. Meanwhile, when rice appeared in Central Asia, the Kushan Empire was already established in northwest India and conquered most of Central Asia and South Asia. The imperial expansion and political unrest may have further fueled the dispersal of crops across Inner Asia. The emergence of rice may also indicate the beginning of the rice-based diet culture's gradual integration with the local wheat-based diet system in Central Asia and finally formed the Central Asia diet system today, like baked dough (Naan), pilaf, and barbecue.

The rice remains in Khalchayan site are the first example of well reported rice remains in Central Asia. The remains are also one of the few ancient cultivated rices found without East Asia, South Asia, and Southeast Asia. It has great value for allowing us to further understand the exchange process of early agricultural activities in the Southern Himalayan route, and also provides new evidence to explain how rice further spread westward to Iran, Europe, and Africa, where rice cultivation activities exist today.