Agriculture's roots go tropical.As early as 7,000 years ago, prehistoric societies in the tropical forests of Central and South America changed over from foraging to food production by cultivating manioc manioc: see cassava. and other plants with edible, starchy roots, a new study finds. Although cultivation appeared later there than in the Middle East, the data support a controversial theory that tropical-forest dwellers cultivated roots and tubers 1. a swelling or protuberance. 2. the essential lesion of tuberous sclerosis, presenting as a pale, firm, nodular, phakomalike glial hamartomatous brain lesion. tuber cine´reum a layer of gray matter forming part of the floor of the third ventricle, to which the infundibulum of the hypothalamus is attached. long before such practices emerged elsewhere among Native Americans, says a team led by archaeologist Dolores R. Piperno of the Smithsonian Tropical Research Institute in Balboa, Panama. Piperno's group recovered starch grains from milling stones found at a Panamanian site dated at between 7,000 and 5,000 years old. Microscopic analysis of the grains identified examples of manioc, arrowroot arrowroot, any plant of the genus Maranta, usually large perennial herbs, of the family Marantaceae, found chiefly in warm, swampy forest habitats of the Americas and sometimes cultivated for their ornamental leaves. The term arrowroot is also used for the easily digestible starch obtained from the rhizomes of M. arundinacea, the true, or West Indian, arrowroot, which is naturalized in Florida. Other plants produce similar starches, e.g., and yams yam, common name for some members of the Dioscoreaceae, a family of tropical and subtropical climbing herbs or shrubs with starchy rhizomes often cultivated for food. The largest genus, Dioscorea, is commercially important in East Asia and in tropical America. The thick rhizomes, often weighing 30 lb (13.6 kg) or more, are used for human consumption and for feeding livestock., the researchers report in the Oct. 19 NATURE. Earlier microscope observations by Piperno had uncovered characteristic grain shapes for these and many other modern species of wild and domesticated plants. The ancient milling stones also contained starch grains from maize, indicating that the site's prehistoric residents grew seed crops as well as root crops root crop, vegetable cultivated chiefly for its edible roots, e.g., the beet, turnip, mangel-wurzel, carrot, and parsnip. All root crops have a large water content and grow best in deeply cultivated soil in cool, overcast weather when the plant's loss of water through transpiration is lowest. Because they require thorough cultivating they are often desirable in a rotation of crops—beets and turnips being most frequently so used., the scientists say. Piperno suspects that the cultivation of manioc, a staple food in the tropics, first occurred in South America and then spread northward. Other researchers have uncovered manioc grains at two sites in Belize that date to 4,700 years ago. |
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