Peanut

Raw Valencia peanuts are 4% water, 48% fat, 25% protein, and 21% carbohydrates (table). In a reference amount of 100 grams (3.5 oz), peanuts provide 2,385 kilojoules (570 kilocalories) of food energy, supply 9 g (0.32 oz) of dietary fiber, and are a rich source (defined as more than 20% of the Daily Value, DV) of several B vitamins, vitamin E, and various dietary minerals, such as manganese, magnesium, and phosphorus. The fats are mainly polyunsaturated and monounsaturated (83% of total fats when combined; table source). Some studies show that regular consumption of peanuts is associated with a lower specific risk of mortality from certain diseases. However, the study designs do not allow cause and effect to be inferred. According to the US Food and Drug Administration, "Scientific evidence suggests but does not prove that eating 1.5 ounces per day of most nuts (such as peanuts) as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease."

The Arachis genus is native to South America, east of the Andes, around Peru, Bolivia, Argentina, and Brazil. Cultivated peanuts (A. hypogaea) arose from a hybrid between two wild species of peanut, thought to be A. duranensis and A. ipaensis. The initial hybrid would have been sterile, but spontaneous chromosome doubling restored its fertility, forming what is termed an amphidiploid or allotetraploid. Genetic analysis suggests the hybridization may have occurred only once and gave rise to A. monticola, a wild form of peanut that occurs in a few limited locations in northwestern Argentina, or in southeastern Bolivia, where the peanut landraces with the most wild-like features are grown today, and by artificial selection to A. hypogaea. The process of domestication through artificial selection made A. hypogaea dramatically different from its wild relatives. The domesticated plants are bushier, more compact, and have a different pod structure and larger seeds. From this center of origin, cultivation spread and formed secondary and tertiary centers of diversity in Peru, Ecuador, Brazil, Paraguay, and Uruguay. Over time, thousands of peanut landraces evolved; these are classified into six botanical varieties and two subspecies (as listed in the peanut scientific classification table). Subspecies A. h. …