A cereal is any of the edible components of the grain (botanically, a type of fruit, called a caryopsis) of cultivated grass, composed of the endosperm, germ, and bran. Cereal grains are grown in greater quantities and provide more food energy worldwide than any other type of crop and are therefore staple crops. Edible grains from other plant families, such as buckwheat (Polygonaceae), quinoa (Amaranthaceae) and chia (Lamiaceae), are referred to as pseudocereals.
In their natural, unprocessed, whole grain form, cereals are a rich source of vitamins, minerals, carbohydrates, fats, oils, and protein. When processed by the removal of the bran, and germ, the remaining endosperm is mostly carbohydrate. In some developing countries, grain in the form of rice, wheat, millet, or maize constitutes a majority of daily sustenance. In developed countries, cereal consumption is moderate and varied but still substantial.
Some grains are deficient in the essential amino acid, lysine. That is why many vegetarian cultures, in order to get a balanced diet, combine their diet of grains with legumes.
Many legumes, however, are deficient in the essential amino acid methionine, which grains contain. Thus, a combination of legumes with grains forms a well-balanced diet for vegetarians. Common examples of such combinations are dal (lentils) with rice by South Indians and Bengalis, dal with wheat in Pakistan and North India, and beans with corn tortillas, tofu with rice, and peanut butter with wheat bread (as sandwiches) in several other cultures, including Americans. The amount of crude protein found in grain is measured as the grain crude protein concentration.
Cereals contain exogenous opioid peptides called exorphins and include opioid food peptides like Gluten exorphin and opioid food peptides. They mimic the actions of endorphines because they bind to the same opioid receptors in the brain.
Agriculture allowed for the support of an increased population, leading to larger societies and eventually the development of cities. It also created the need for greater organization of political power (and the creation of social stratification), as decisions had to be made regarding labor and harvest allocation and access rights to water and land. Agriculture bred immobility, as populations settled down for long periods of time, which led to the accumulation of material goods.
Early Neolithic villages show evidence of the development of processing grain. The Levant is the ancient home of the ancestors of wheat, barley and peas, in which many of these villages were based. There is evidence of the cultivation of figs in the Jordan Valley as long as 11,300 years ago, and cereal (grain) production in Syria approximately 9,000 years ago. During the same period, farmers in China began to farm rice and millet, using man-made floods and fires as part of their cultivation regimen. Fiber crops were domesticated as early as food crops, with China domesticating hemp, cotton being developed independently in Africa and South America, and Western Asia domesticating flax. The use of soil amendments, including manure, fish, compost and ashes, appears to have begun early, and developed independently in several areas of the world, including Mesopotamia, the Nile Valley and Eastern Asia.
The first cereal grains were domesticated by early primitive humans. About 8,000 years ago, they were domesticated by ancient farming communities in the Fertile Crescent region. Emmer wheat, einkorn wheat, and barley were three of the so-called Neolithic founder crops in the development of agriculture. Around the same time, millets and rices were starting to become domesticated in East Asia. Sorghum and millets were also being domesticated in sub-Saharan West Africa.