section_path: Evolution/History
section_name: History
paragraph_text: History
  
  Oryza sativa rice was first domesticated in China 9,000 years ago, by people of Neolithic cultures in the Upper and Lower Yangtze, associated with Hmong-Mien -speakers and pre-Austronesians, respectively. The functional allele for nonshattering, the critical indicator of domestication in grains, as well as five other single-nucleotide polymorphisms, is identical in both indica and japonica. This implies a single domestication event for O. sativa. Both indica and japonica forms of Asian rice sprang from a single domestication event in China from the wild rice Oryza rufipogon. Despite this evidence, it appears that indica rice arose when japonica arrived in India about 4,500 years ago and hybridised with another rice, whether an undomesticated proto- indica or wild O. nivara.
  
  Rice was introduced early into Sino-Tibetan cultures in northern China by around 6000 to 5600 years ago, and to the Korean peninsula and Japan by around 5500 to 3200 years ago. It was also carried into Taiwan by the Dapenkeng culture by 5500 to 4000 years ago, before spreading southwards via the Austronesian migrations to Island Southeast Asia, Madagascar, and Guam, but did not survive the voyage to the rest of the Pacific. It reached Austroasiatic and Kra-Dai -speakers in Mainland Southeast Asia and southern China by 5000 years ago.
  
  Rice spread around the rest of the world through cultivation, migration and trade, eventually to the Americas as part of the Columbian exchange after 1492. The now less common Oryza glaberrima (African rice) was independently domesticated in Africa around 3,000 years ago, and introduced to the Americas by the Spanish. In British North America by the time of the start of the American War of Independence, rice had become the fourth most valuable export commodity behind only tobacco, wheat, and fish.