History of rice cultivation
The history of rice cultivation is an interdisciplinary subject that studies archaeological and documentary evidence to explain how rice was first domesticated and cultivated by humans, the spread of cultivation to different regions of the planet, and the technological changes that have impacted cultivation over time.
The current scientific consensus, based on archaeological and linguistic evidence, is that Oryza sativa rice was first domesticated in the Yangtze River basin in China 9,000 years ago. Cultivation, migration and trade spread rice around the world—first to much of east Asia, and then further abroad, and eventually to the Americas as part of the Columbian exchange.
The now less common Oryza glaberrima rice, also known as African Rice, was independently domesticated in Africa around 3,000 years ago. O. glaberrima spread to the Americas through the transatlantic slave trade although how is not clear. It is still commonly grown in West Africa and is grown in a number of countries in the Americas. There are also several crosses of O. glaberrima and O. sativa.
Four species of rice that form the genus Zizania, commonly known as wild rice are native to and cultivated in North America, where the grain is used, as well as in China, where the plant's stem is used as a vegetable. Wild rice and domesticated rice belong to the same botanical tribe, Oryzeae. Wild rice is also cultivated in Hungary and Australia.
Since its spread, rice has become a global staple crop important to food security and food cultures around the world. Local varieties of Oryza sativa have resulted in over 40,000 cultivars of various types. More recent changes in agricultural practices and breeding methods as part of the Green Revolution and other transfers of agricultural technologies has led to increased production in recent decades.
History
Asia
The scientific consensus based on archaeological and linguistic evidence, is that rice was first domesticated in the Yangtze River basin in China. Because 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, Vaughan et al. determined a single domestication event for O. sativa. This was supported by a genetic study in 2011 that showed that all forms of Asian rice, both indica and japonica, sprang from a single domestication event that occurred some 9,000 years ago in China from the wild rice Oryza rufipogon. A more recent population genomic study indicates that japonica was domesticated first, and that indica rice arose when japonica arrived in India about ~4,500 years ago and hybridized with an undomesticated proto-indica or wild O. nivara.There are two most likely centers of domestication for rice as well as the development of the wetland agriculture technology. The first is in the lower Yangtze River, believed to be the homelands of the pre-Austronesians and possibly also the Kra–Dai, and associated with the Kauhuqiao, Hemudu, Majiabang, Songze, Liangzhu, and Maqiao cultures. It is characterized by pre-Austronesian features, including stilt houses, jade carving, and boat technologies.
The second is in the middle Yangtze River, believed to be the homelands of the early Hmong–Mien speakers and associated with the Pengtoushan, Nanmuyuan, Liulinxi, Daxi, Qujialing, and Shijiahe cultures. Both of these regions were heavily populated and had regular trade contacts with each other, as well as with early Austroasiatic speakers to the west, and early Kra–Dai speakers to the south, facilitating the spread of rice cultivation throughout southern China.
Rice was gradually introduced north into the early Sino-Tibetan Yangshao and Dawenkou culture millet farmers, either via contact with the Daxi culture or the Majiabang-Hemudu culture. By around 4000 to 3800 BC, they were a regular secondary crop among southernmost Sino-Tibetan cultures. It did not replace millet, largely because of different environment conditions in northern China, but it was cultivated alongside millet in the southern boundaries of the millet-farming regions. Conversely, millet was also introduced into rice-farming regions.
By the late Neolithic, population in the rice cultivating centers had increased rapidly, centered around the Qujialing-Shijiahe culture and the Liangzhu culture. There was also evidence of intensive rice cultivation in paddy fields as well as increasingly sophisticated material cultures in these two regions. Both the number of settlements and overall settlement sizes increased among the Yangtze cultures, leading some archeologists to characterize them as true states, with clearly advanced socio-political structures. However, it is unknown if they had centralized control.
Liangzhu and Shijiahe declined abruptly in the terminal Neolithic. With Shijiahe shrinking in size, and Liangzhu disappearing altogether. This is largely believed to be the result of the southward expansion of the early Sino-Tibetan Longshan culture. Fortifications like walls are common features in settlements during this period, indicating widespread conflict. This period also coincides with the southward movement of rice-farming cultures to the Lingnan and Fujian regions, as well as the southward migrations of the Austronesian, Kra–Dai, and Austroasiatic-speaking peoples to Mainland Southeast Asia and Island Southeast Asia. A genomic study also indicates that at around this time, a global cooling event led to tropical japonica rice being pushed southwards, as well as the evolution of temperate japonica rice that could grow in more northern latitudes.
Genomic studies suggests that indica rice was later introduced back to China from India between 2,000 and 1,400 years ago.
Southeast Asia
The spread of japonica rice cultivation to Southeast Asia started with the migrations of the Austronesian Dapenkeng culture into Taiwan between 3500 and 2000 BC. The Nanguanli site in Taiwan, dated to ca. 2800 BC, has yielded numerous carbonized remains of both rice and millet in waterlogged conditions, indicating intensive wetland rice cultivation and dryland millet cultivation. A multidisciplinary study using rice genome sequences indicate that tropical japonica rice was pushed southwards from China after a global cooling event that occurred approximately 4,200 years ago.File:Likely_routes_of_early_rice_transfer,_and_possible_language_family_homelands_.png|left|thumb|320x320px|Possible language family homelands, and likely routes of early rice transfer. The approximate coastlines during the early Holocene are shown in lighter blue.
From about 2000 to 1500 BC, the Austronesian expansion began, with settlers from Taiwan moving south to colonize Luzon in the Philippines, bringing rice cultivation technologies with them. From Luzon, Austronesians rapidly colonized the rest of Island Southeast Asia, moving westwards to Borneo, the Malay Peninsula and Sumatra; and southwards to Sulawesi and Java. By 500 BC, there is evidence of intensive wetland rice agriculture already established in Java and Bali, especially near very fertile volcanic islands.
File:Pana_Banaue_Rice_Terraces_.jpg|thumb|Banaue Rice Terraces in Luzon, Philippines
It has been speculated the rice did not survive the Austronesian voyages into Micronesia due to the sheer distance of ocean they were crossing and the lack of abundant rain. These voyagers became the ancestors of the Lapita culture. By the time they migrated southwards to the Bismarck Archipelago, they had already lost the technology of rice farming. However, there is no archaeological record of rice in Polynesia and Micronesia before or during the time of Lapita pottery fitting the hypothesis.
Rice, along with other Southeast Asian food plants, were also later introduced to Madagascar, the Comoros, and the coast of East Africa by around the 1st millennium AD by Austronesian settlers from the Greater Sunda Islands.
Much later Austronesian voyages from Island Southeast Asia succeeded in bringing rice to Guam during the Latte Period. Guam is the only island in Oceania where rice was grown in pre-colonial times.
Within Mainland Southeast Asia, rice was presumably spread through river trade between the early Hmong–Mien speakers of the Middle Yangtze basin and the early Kra–Dai speakers of the Pearl River and Red River basins, as well as the early Austroasiatic speakers of the Mekong River basin. Evidence for rice cultivation in these regions, dates to slightly later than the Dapenkeng settlement of Taiwan, at around 3000 BC. Southward migrations of the Austroasiatic and Kra–Dai speakers introduced it into Mainland Southeast Asia. The earliest evidence of rice cultivation in Mainland Southeast Asia come from the Ban Chiang site in northern Thailand ; and the An Sơn site in southern Vietnam. A genomic study indicates that rice diversified into Maritime Southeast Asia between 2,500 and 1,500 years ago.