<P> Records from the Warring States, Qin Dynasty, and Han Dynasty provide a picture of early Chinese agriculture from the 5th century BC to 2nd century AD which included a nationwide granary system and widespread use of sericulture . An important early Chinese book on agriculture is the Chimin Yaoshu of AD 535, written by Jia Sixia . Jia's writing style was straightforward and lucid relative to the elaborate and allusive writing typical of the time . Jia's book was also very long, with over one hundred thousand written Chinese characters, and it quoted many other Chinese books that were written previously, but no longer survive . The contents of Jia's 6th century book include sections on land preparation, seeding, cultivation, orchard management, forestry, and animal husbandry . The book also includes peripherally related content covering trade and culinary uses for crops . The work and the style in which it was written proved influential on later Chinese agronomists, such as Wang Zhen and his groundbreaking Nong Shu of 1313 . </P> <P> For agricultural purposes, the Chinese had innovated the hydraulic - powered trip hammer by the 1st century BC . Although it found other purposes, its main function to pound, decorticate, and polish grain that otherwise would have been done manually . The Chinese also began using the square - pallet chain pump by the 1st century AD, powered by a waterwheel or oxen pulling an on a system of mechanical wheels . Although the chain pump found use in public works of providing water for urban and palatial pipe systems, it was used largely to lift water from a lower to higher elevation in filling irrigation canals and channels for farmland . By the end of the Han dynasty in the late 2nd century, heavy ploughs had been developed with iron ploughshares and mouldboards . These would slowly spread west, revolutionizing farming in Northern Europe by the 10th century . (Glick, however, argues for a development of the Chinese plough as late as the 9th century, implying its spread east from similar designs known in Italy by the 7th century .) </P> <P> Asian rice was domesticated 8,200--13,500 years ago in China, with a single genetic origin from the wild rice Oryza rufipogon, in the Pearl River valley region of China . Rice cultivation then spread to South and Southeast Asia . </P> <P> The major cereal crops of the ancient Mediterranean region were wheat, emmer, and barley, while common vegetables included peas, beans, fava, and olives, dairy products came mostly from sheep and goats, and meat, which was consumed on rare occasion for most people, usually consisted of pork, beef, and lamb . Agriculture in ancient Greece was hindered by the topography of mainland Greece that only allowed for roughly 10% of the land to be cultivated properly, necessitating the specialized exportation of oil and wine and importation of grains from Thrace (centered in what is now Bulgaria) and the Greek colonies of southern Russia . During the Hellenistic period, the Ptolemaic Empire controlled Egypt, Cyprus, Phoenicia, and Cyrenaica, major grain - producing regions that mainland Greeks depended on for subsistence, while the Ptolemaic grain market also played a critical role in the rise of the Roman Republic . In the Seleucid Empire, Mesopotamia was a crucial area for the production of wheat, while nomadic animal husbandry was also practiced in other parts . </P>

About 12 000 years ago what environmental changes created a shift in food production ​