<P> The history of agriculture records the domestication of plants and animals and the development and dissemination of techniques for raising them productively . Agriculture began independently in different parts of the globe, and included a diverse range of taxa . At least eleven separate regions of the Old and New World were involved as independent centers of origin . </P> <P> Wild grains were collected and eaten from at least 20000 BC . From around 9500 BC, the eight Neolithic founder crops--emmer wheat, einkorn wheat, hulled barley, peas, lentils, bitter vetch, chick peas, and flax--were cultivated in the Levant . Rye may have been cultivated earlier but this remains controversial . Rice was domesticated in China by 6200 BC with earliest known cultivation from 5700 BC, followed by mung, soy and azuki beans . Pigs were domesticated in Mesopotamia around 11000 BC, followed by sheep between 11000 BC and 9000 BC . Cattle were domesticated from the wild aurochs in the areas of modern Turkey and Pakistan around 8500 BC . Sugarcane and some root vegetables were domesticated in New Guinea around 7000 BC . Sorghum was domesticated in the Sahel region of Africa by 5000 BC . In the Andes of South America, the potato was domesticated between 8000 BC and 5000 BC, along with beans, coca, llamas, alpacas, and guinea pigs . Bananas were cultivated and hybridized in the same period in Papua New Guinea . In Mesoamerica, wild teosinte was domesticated to maize by 4000 BC . Cotton was domesticated in Peru by 3600 BC . Camels were domesticated late, perhaps around 3000 BC . </P> <P> The Bronze Age, from c. 3300 BC, witnessed the intensification of agriculture in civilizations such as Mesopotamian Sumer, ancient Egypt, the Indus Valley Civilisation of South Asia, ancient China, and ancient Greece . During the Iron Age and era of classical antiquity, the expansion of ancient Rome, both the Republic and then the Empire, throughout the ancient Mediterranean and Western Europe built upon existing systems of agriculture while also establishing the manorial system that became a bedrock of medieval agriculture . In the Middle Ages, both in the Islamic world and in Europe, agriculture was transformed with improved techniques and the diffusion of crop plants, including the introduction of sugar, rice, cotton and fruit trees such as the orange to Europe by way of Al - Andalus . After the voyages of Christopher Columbus in 1492, the Columbian exchange brought New World crops such as maize, potatoes, sweet potatoes, and manioc to Europe, and Old World crops such as wheat, barley, rice, and turnips, and livestock including horses, cattle, sheep, and goats to the Americas . </P> <P> Irrigation, crop rotation, and fertilizers were introduced soon after the Neolithic Revolution and developed much further in the past 200 years, starting with the British Agricultural Revolution . Since 1900, agriculture in the developed nations, and to a lesser extent in the developing world, has seen large rises in productivity as human labour has been replaced by mechanization, and assisted by synthetic fertilizers, pesticides, and selective breeding . The Haber - Bosch process allowed the synthesis of ammonium nitrate fertilizer on an industrial scale, greatly increasing crop yields . Modern agriculture has raised social, political, and environmental issues including water pollution, biofuels, genetically modified organisms, tariffs and farm subsidies . In response, organic farming developed in the twentieth century as an alternative to the use of synthetic pesticides . </P>

Where is most of the agriculture practiced on earth