Supercrop: the yam bean, a tuber undaunted by drought, poor soil, or insects, produces astonishing yields. The crop is the focus of a worldwide effort to unlock its potential

Natural History, April, 2004 by Marten Sorensen

The Amazonian yam bean species, P. tuberosus, occurs as far north as Venezuela and as far south as Paraguay; but its history is more obscure than that of the Mexican species. Part of the reason for the obscurity is doubtless that the humid tropical lowlands of South America can be quite inhospitable to archaeological remains. But a combination of factors suggests that P. tuberosus, too, has a long history of domestication: The plant is widely distributed. It has a multitude of vernacular names (in various language groups), including ashipa, chuin, iwa, jacatupe, jiquima, mbacucu, nupe, poi, and yushpe. And in many rural areas it is still grown by indigenous peoples according to traditional cultivation practices, such as slash and burn.

Some ethnobotanists and anthropologists are convinced that root and tuber crops were among the first plants to be domesticated. After all, it is easy to imagine a transition from gathering roots in the local environment to cultivating them close to the family dwelling. In fact, the edible tubers of the Amazonian species of Pachyrhizus are thought to have been gathered in Peru before the advent of agriculture--that is, before 8500 B.C. And, as with other traditional root and tuber crops from South America that were later cultivated in the Caribbean, the presence of P. tuberosus in Cuba, Hispaniola, Jamaica, Puerto Rico, and Trinidad today suggests that the crop was introduced by Amerindians from northern South America, and thus points to a history of cultivation that predates Columbus.

The earliest European report on the cultivation of the Amazonian yam bean dates to the work of a mid-sixteenth century missionary who describes how tribes living along the coastline of Brazil used the plant. Some four centuries later, two German-Brazilian investigators--the emigre botanist and chemist Theodor Peckolt and his soil, Custavo Peckolt--reported that it was cultivated as food for slaves on large estates. The long, thick tuberous roots, they noted, were dried and smoked, turning them into what the Peckolts called "vegetable sausage."

The third cultivated species, the Andean yam bean (P. ahipa, locally known as ahipa or ajipa), rarely occurs today outside Bolivia. But it, too, has a long history of pre-Columbian--indeed, pre-Inca--cultivation in the Andes. Dried ahipas were among the provisions buried with the dead two millennia ago on the south coast of Peru, accompanying the hundreds of lavishly wrapped mummies discovered beneath the arid sands of the Paracas Peninsula. The ahipa was also depicted on the embroidered cloaks, knitted textiles, and imaginatively sculpted and painted ceramics produced by such thriving pre-Columbian societies as the Nazca, the Moche, and the Chimu.

The various species and cultivars have found their way into a dizzying array of utilizations. In seventeenth-century China, diced yam beans were preserved in syrup and eaten as candy; during the same period in Mexico, the diced tuber was wrapped in sweet dough, then placed in syrup-filled jars and exported to Spain. Today Mexicans often put jicamas inside pinatas--the decorative papier-mache containers that are filled with goodies and then smashed to pieces at festive occasions. Taiwanese fishermen often take jicamas with them on long expeditions, as nutritious and imperishable provisions. In the towns and villages of southern Bolivia--notably in Tarija--during the Corpus Christi celebrations in June, people sip fermented or unfermented fruit juices from vessels formed of hollowed--out ahipas ornamented with flowers. And thirsty Peruvian field laborers in the high, dry Andean forests, often finding themselves far from sources of freshwater, simply harvest, peel, and squeeze a yam bean to get a refreshing drink.