An ancient culture in southern Peru cultivated corn some 4,000 years ago, about a thousand years earlier than previously believed, a new study suggests.
Researchers excavating a site in the Andean highland town of Waynuna found both corn leaf and corncob remains in the ruins of a house at least 3,600 years old.
Perhaps even more important, the scientists say, is that they found arrowroot remains at the same dig site.
The presence of this edible root confirms archeologists' suspicions that people in the eastern lowland forests—where the plant was grown—made contact with people in the highlands—where the root was consumed.
"Archaeologists have suspected that there was an important connection between the two areas based upon iconographic evidence and some coastal finds," said Linda Perry, the lead author on the study.
Perry is an archaeobiologist with the Smithsonian National Museum of Natural History in Washington, D.C. She conducted the research with Dolores Piperno, a staff scientist at the Smithsonian Tropical Research Institute in Panama and a National Geographic Society grantee.
Perry added that "our arrowroot fossils are the first highland evidence documenting this connection. Our finds indicate that the connection was early and of long duration."
She and her team describe their findings in this month's issue of the journal Nature.
The Waynuna site, excavated by a team from the University of Maine in Orono, lies in Peru's Cotahuasi Valley, about 200 miles (320 kilometers) west of Lake Titicaca (see map (http://www.nationalgeographic.com/xpeditions/atlas/index.html?Parent=sameri&Rootmap=peru&Mode=d&SubMode=w)). The area has been occupied since about 13,000 years ago.
Human cultivation of corn probably first began in Mexico almost 10,000 years ago. Then people carried it south to Ecuador by about 7,000 years ago.
In Peru, "our dates indicate a migration of the crop down the Andean mountain chain and an acceptance of maize into the local diet quite early, by 4,000 years ago," Perry said.
The researchers determined that damage in the maize granules found at Waynuna was due to grinding and pounding from the outside and not caused by rotting from the inside.
The researchers also found corn remains on tools that were used for grinding and pounding corn to make flour.
There were two different kinds of corn being used at the site, one that was soft enough to be made into flour and another with a harder kernel similar to modern popcorn.
The Waynuna site, they conclude, was a place where corn was both grown and processed more than 2,000 years before the appearance of the great South American empires built on corn cultivation—the Wari, the Tiwanaku, and the Inca .
Uprooting Conventional Methods
For some experts, though, the arrowroot find is more interesting than the evidence of early corn use.
Richard Burger, a professor of archeology at Yale University in New Haven, Connecticut, who was not involved in the study, said that most scholars have already accepted that corn was cultivated in central and northern Peru around this time.
But, he said, "the identification of arrowroot is in some respects more exciting and unexpected, particularly since it is relevant to models of highland/eastern lowland interaction during the early stages of agriculture."
Arrowroot cannot be cultivated at high altitudes, so the material must have been brought to Waynuna—11,800 feet (3,600 meters) above sea level—from the Amazonian rain forest to the east.
This means that goods and people must have moved between the eastern lowlands and the Andean highlands, and that arrowroot was a trade commodity well before European contact.
"There is no question that this is an important contribution to the field," Burger said.
The researchers were also praised for their cutting-edge analysis techniques.
Because Waynuna experiences seasonal rainfall, plant material decomposes rapidly on the ground. But Perry's team was able to perform microscopic analyses of starches and silica phytoliths, which are fossilized plant remains.
Jose Iriarte, professor of archaeology at the University of Exeter in England, said that the research was "a welcome expansion in the application of microbotanical techniques to the Central Andean highlands."
"Plants are one of the most important items that people exchanged in the past," Iriarte said.
"And documenting these interactions will prove crucial to unraveling the connections between the eastern tropical forest and the Andean highlands on the brink of complex societies."