Colorado researchers have found the earliest direct evidence of manioc cultivation in the Americas, the remains of a 1,400-year-old field in El Salvador that was buried by volcanic ash shortly after the crop was harvested.
Manioc, also known as cassava, produces the highest yield of food energy of any cultivated crop, and its widespread use by the Maya could help explain how they sustained high population densities, said archeologist Payson Sheets of the University of Colorado, who made the discovery in the village of Ceren.
"We have always suspected strongly that people did cultivate manioc, but we have never had direct evidence of it," said archeologist David Freidel of Southern Methodist University, who was not involved in the research. "It's not going to be surprising to [people in] the field, but it is very gratifying that we have evidence substantiating it."
Ceren, about 15 miles west of San Salvador, has been called the American Pompeii. A village of about 200 people, Ceren was buried by the eruption of a volcano now known as Laguna Caldera in AD 590 that covered the village with as much as 17 feet of ash, preserving houses and their contents in remarkable detail.
Researchers think, based on the height of the corn in the fields and the fact that farming tools had been put away but bedrolls had not been unrolled, that the eruption occurred early in the evening in August. An earthquake shortly before the eruption apparently scared the villagers out of their homes. No bodies have been found.
Sheets and his colleagues discovered the evidence of manioc cultivation in June when they were excavating an underground anomaly revealed by ground-penetrating radar, the University of Colorado said Monday.
The manioc was long gone. What they found were holes left behind in the solidified ash as the manioc rotted away. They carefully filled the holes with plaster of Paris, then chipped away the ash to reveal what had been there.
They found planting beds about 3 feet wide and 2 feet high. They do not yet know how long the rows were.
The crop had apparently just been harvested, and only a few manioc tubers remained. The beds had been replanted with manioc stalks placed horizontally in the soil to regenerate bushes for the next growing cycle. The evidence indicates that the planting was done "just hours before the eruption," Sheets said.
"We felt like we were right on the heels of these ancient people because of the exquisite preservation provided by the volcanic ash," he said.
The idea that manioc was used by the Maya was first proposed in 1966 by archeologist Ben Bronson.
The tuber provides six to 10 times as much food energy per acre as corn, making it a feasible food source to have supported a population that researchers were concluding reached hundreds per square kilometer.
The tuber can be cooked much like a potato, or made into puddings and other foods that are high in sugars. The leaves are high in protein. The plant is widely cultivated in the Americas today.
But finding evidence that the Maya farmed it has been frustrating, Freidel said. The most direct evidence before now has been the discovery of obsidian tools that might have been used for scraping the tubers, he said.
The new discovery may help researchers develop evidence of manioc cultivation at other locations, Sheets said.
Researchers at the Smithsonian Institution in Washington are developing soil analysis techniques to look for starch grains like those Sheets found at Ceren.