Cultivation of the soil, including the allied pursuits of gathering crops and rearing livestock. The ‘Neolithic revolution’, the change from an economy based on hunting and gathering to one based on settled agriculture, is thought to have begun in many independent centres around the world, at very roughly the same time (c.9000 bc): changes in climate and population growth may have stimulated this process. Archaeological evidence suggests at least three independent centres of origin for agriculture based on grain crops (the Near East, the Far East, and meso‐America), plus other sites (for example, Peru and Indonesia) where root vegetables formed the main crops. The most complete evidence has come from the Near East, where domesticated barley and emmer wheat strains have been found which date from about 8000 bc. Domesticated animals (e.g. sheep and goats) were reared in large numbers from at least 7000 bc, and there is evidence for the use of the ox‐drawn wooden plough from 5000 bc. In the early civilizations of Babylonia, Egypt, the Indus Valley, and China (from c.3000 bc), large‐scale irrigation systems were developed.

Agricultural practices spread gradually from the different centres to other parts of the world, and were adapted to local conditions; many different field systems evolved. In Europe and the Mediterranean, practices, once established, remained basically unchanged for many years. Roman farmers used an ox‐drawn, wheelless plough with iron shares or blades. They sowed seed by hand, harvested using a curved sickle, threshed grain with a hand flail, and winnowed it by throwing it into the air and letting the wind carry away the chaff. By the 4th century ad, high labour input, the transplanting of seedlings, and use of fertilizers were producing cereal yields in China not matched elsewhere until the 19th century. In the Americas, maize was the main crop in some areas, the potato in others. The llama was domesticated as a beast of burden, while the alpaca was kept for its wool, and the guinea‐pig for meat. In medieval Europe, slow improvements were made in agricultural practice, particularly in northern areas. From the 5th to the 12th centuries, agricultural land was created by forest clearance, or was reclaimed from marshland and the sea. From the late 13th to the early 15th centuries, much arable land fell into disuse due to the effects of floods, famine, plague, and wars. Recovery began slowly in the 15th century. In the 17th and 18th centuries several different developments led to improvements in crop yields and in livestock production. In particular, the Agricultural Revolution of 18th‐century Britain introduced new, more efficient practices into farming. Principal among these was the Norfolk four‐course system, in which grain and fodder or grazing crops were grown in a four‐year rotation. The effects of this system were cumulative: grazing animals manured the land and increased its fertility, while the growing of winter fodder and summer grazing crops meant that animals were better fed, and more productive. In the 18th century selective breeding was introduced, and the Rotherham plough (the forerunner of the modern plough) was developed, along with a variety of simple machines for threshing, chopping animal feed, hoeing, and seed drilling. However, it was not until the mid‐19th century that agricultural machinery, for example the reaper and the traction‐engine, began to be adopted by farmers. The 19th century also saw the development of agricultural science, with the introduction of the earliest chemical and synthetic fertilizers, and the opening of agricultural research stations in several countries. During this period large areas of the USA, Canada, South America, and Australia were settled: huge sheep and cattle ranches were established, and large areas were given over to wheat farming. In colonial countries, plantation farming of beverage crops, rubber, and sugar cane expanded tremendously, although these developments had little effect on indigenous agricultural practices. Much of the cheap food generated by the opening up of these new areas was exported to Europe. The 20th century has seen far‐reaching changes in farming practices. The internal‐combustion engine has replaced steam‐power for agricultural machinery, and improved transport has led to the development of a world market for some agricultural products. The green revolution saw increased crop production in developing countries. From 1965 to the early 1990s, world cereal production increased by over 70%. Thus India, for example, which formerly suffered regularly from famine and was forced to spend scarce foreign exchange on food imports is now self‐sufficient in food although its population has doubled since independence in 1947. Agrochemicals were being used in huge quantities by the 1960s, but since that time the hazards of indiscriminate pesticide use have led to the development of other strategies such as the breeding of disease‐resistant plant strains and the use of biological methods of pest control favoured by organic farmers. Genetic development of plant strains and intensive animal breeding have greatly increased the productivity of croplands and livestock in developed countries while the production of genetically modified food has proved controversial. In the UK genetically modified food is generally not sold because of public opposition.