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PART III Legumes For much of their protein supply, the Incas depended on the common bean, a plant of Central American and Mexican origin. But at high elevations the common bean performs badly it grows slowly and its seeds take too long to cook because water boils at lower temperatures. As a result, ancient Andean peoples developed their own legumes: the large-seeded lima bean (see opposite), basul, nunas, and tarwi. It is important to give more research attention to all of these. While enormous resources have been expended in recent decades on grasses such as rice, wheat, corn, sorghum, and barley, in developing countries especially, the advancement of legumes has lagged. Yet the cultivation of legumes is the most practical and quickest way to augment the production of food proteins. This section details the little-known Andean legumes basul, nunas, and tarwi. The underexploited promise of the lima bean is detailed in a companion report. Ahipa and pacay (ice-cream beans) are also legumes, but are handled in the roots and fruits sections of this report (see pages 39 and 2771. All of the Andean legumes described here have shown unusual promise. Basul and pacay are tree crops with exceptional potential for use in reforestation and the reclamation of wasteland. The nunas are particularly interesting because the kernels burst upon heating, which makes them a bean counterpart of popcorn. This characteristic is especially useful since the grains become edible without the need for grinding or extensive cooking. And tarwi rivals soybeanthe world's premier protein cro~in its composition and nutritive value. ' See companion report, Tropical Legumes: Resources for the Future. National Research Council. 1979. National Academy Press, Washington, D.C. 162
LEGUMES 163 THE LIMA BEAN To provide perspective on the possible future adoption of the under- exploited Andean legumes described in the following section, it seems instructive to consider the success of the one Andean legume that has already achieved worldwide renown. The modern, large-seeded lima beans (Phaseolus lunatus) trace back to Peru. Indeed, they are named for the city where they were probably picked up and distributed throughout the world. Europeans first encoun- tered the plant 400 years ago in the vicinity of what is now Lima. Large lima beans were well known to the Incas and their predecessors, especially in the river valleys cutting across the coastal desert of Peru. Wild types are found in parts of the Andes from Peru to Argentina. However, like many other species, it may have first been domesticated on the eastern slope of the Andean highlands in warm, humid lands. But, if so, the people on the western side of the Andes learned to appreciate it at an early time. Limas have been found in excavations in coastal Peru dated at 6000-5000 B.C. A small-seeded (sieve) type is found in Central America and Mexico, but the earliest record of it is 500-300 B.C. Thus, there probably were two separate domestications of different lima bean strains; the small type in Central America, the large type in South America. Exactly how lima beans left the Americas is not known, but since the time of Columbus they have become widely distributed, particularly in the tropics. In fact, they are one of the most widely cultivated pulse crops, both in temperate and subtropical regions. Spanish galleons took the small-seeded type across the Pacific to the Philippines, and from there it spread through Asia. It is now widely grown in Burma, for instance. Slave traders took limes from Brazil to Africa. At an early date, they reached Madagascar. It is now the main pulse crop in the rain forests of tropical Africa. In many such areas, lima beans have escaped from cultivation and maintain themselves in a wild state. They are exported (under the name "white butter beans") from Madagascar. The sieve type had already been spread from Mexico and Central America to New England by the time Europeans arrived. The large-seeded Peruvian lima types are known to have been carried by ship, perhaps as a curiosity, to be grown on a farm in New York State in 1824. Today, both large-seeded lima beans and sieves are an important United States crop, grown for canning, freezing, and production of dried beans. They are also important as a fresh vegetable commercial production running to more than 100,000 tons each year, chiefly in California.