Rice is the main food source for about half the population of the Earth, and it is arguably one of the most important foods for human beings. The origins of rice, as well as it spread is a key point of study for many biologists and archaeologists. With advances in archaeobotany and molecular biology, we now understand that in the Yangtze region of China about 10,000 years ago cultivated rice was domesticated into japonica rice (Oryza sativa japonica). This rice spread to Japan as well as southeast Asia. About 5,000 to 4,000 years ago this rice was hybridized with native wild rices in southern Asia and gradually formed the indica rice (Oryza sativa indica) to become the main crop in South Asia today. Most of these studies have focused on the origins of rice in East Asia and its spread to South and Southeast Asia. Little is known about how rice spread west into Central Asia, Europe and Africa.
The importance of the ancient Silk Road cannot be ignored to understand the spread of rice. Therefore, studying the time and location of rice emergence in Central Asia can help elucidate the spread and process of rice agriculture, and also add an important understanding of early crop technology research.
Studying the agricultural remains of the Khalchayan site in Uzbekistan, the Li Xiaoqiang research group at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (IVPP, CAS) and other researchers from the College of Cultural Heritage at the Northwest University, China and the Institute of Archaeology, Uzbekistan Academy of Sciences reported their findings of prehistoric rice agriculture in Central Asia.
Khalchayan was a city in southeastern Uzbekistan. Researchers discovered these people used rice by using flotation method to obtain a large amount of botanical materials from the cultural layer in southwest part of the site. The rice remains in Khalchayan site is the first well reported rice remain in Central Asia. The AMS 14C dating results showed that the age of the rice remains in the site are 1714-1756 cal. B.P., which falls during the Kushan period. In addition to the rice remains they also found these people cultivated wheat, barley, peas, millet, grapes, and flax. These crops include both West Asian and East Asian origin, which illustrates a diverse and complex oasis farming system as well as a exchanges of crop.
Compared to wheat and millet, rice cultivation requires a lot of heat and water. This makes it difficult to cultivate in arid regions. But combining the rice remains with the archaeological records of the irrigation system existing in other local oases agricultural archeological sites during Kushan period, researchers believe these people had the technology to cultivate rice locally during that time.
Morphological studies of the rice from this site, show similarities to japonica rice. That indicates the possibility of rice in Central Asia was spread from South Asia. As rice appeared in Central Asia, the Kushan Empire was already established in northwest India and conquered most part of Central Asia and South Asia. The imperial expansion and political unrest may have further fueled the dispersal of crops throughout Inner Asia.
The emergence of rice may also indicate the introduction of rice-based diet culture to an already established local wheat-based diet system in Central Asia. This is the oldest evidence of cultivated rice found outside of East Asia and has great value to understanding exchange process of the early agricultural activities in the Southern Himalayan route. Furthermore, this findings provides new evidence to explain how rice further spreads westward to Iran, Europe, and Africa, where rice cultivation activities exist today.