Archeologists have long credited the Iroquois with spreading agriculture throughout the Northeast.
Take the period 1,000 years ago in central New York when the small, nomadic settlements of the Point Peninsula people (named after the Lake Ontario region where their pottery was first discovered) were replaced by large Iroquois villages, marked by the classic longhouse. The speed of this turnover—perhaps a few decades—led Penn State anthropologist Dean Snow to hypothesize that the wigwam-dwelling Point Peninsula people were pushed out by Iroquois bringing agriculture.
But to graduate student Janet Schulenberg, that model seemed too simple. "Elsewhere we see hunting and gathering peoples gradually settling down and beginning to cultivate wild plants," she says. "How do we know this wasn't already occurring before the Iroquois migration? The Iroquois have been studied since 1680, but we do not know why they changed house styles or adopted corn."
The key is to find the earliest evidence of agriculture in the area. For Schulenberg, that means teasing out the remains of ancient corn.
One common technique for isolating plant residues from soil, she says, is flotation: Dirt from an archeological site is submerged in water; lighter objects like plant remains float to the surface. But almost all of the known Iroquois sites were excavated during the 1950s, long before this technique became common, and are now hopelessly contaminated. Chemical analysis of skeletons can provide clues to what an individual ate, but the Iroquois, like most Native Americans, view the exhumation of their dead as an affront, ruling out that option as well.
So Schulenberg, inspired by early explorers' accounts of how the Iroquois ate—keeping a pot of corn mash soup bubbling over the fire all day and dipping into it whenever they were hungry —turned to pottery. The corn mash, she reasoned, would leave a ring of burnt carbon around the inside of the pot. The trick would be to confirm the presence of maize in the carbon residue.
Carbon exists in several forms, or isotopes, Schulenberg explains. These isotopes are distinguished by their atomic weight, which is calculated by counting the number of protons and neutrons in their nuclei. Isotopes may be stable, meaning that their atomic bonds do not weaken over time, or unstable, giving off small levels of radiation as they decay at a set rate. Of the stable isotopes, the most common is carbon 13; of the unstable isotopes, the most common is carbon 14. As it turns out, temperate-zone plants are low in carbon 13, but corn, a native of tropical Mexico, is high in it. Schulenberg could identify maize on a pot by the carbon 13 ratio, then date the residue using radiocarbon dating, which measures the decay of carbon 14. Together, the two analyses would pinpoint when corn was present in the area.
To see if her method worked, Schulenberg first analyzed potsherds from Pennsylvania. Three samples dated from 200 A.D., well before corn had been introduced, and six were from people historically known to eat corn. "The method correctly showed no corn on the early pots and corn on the historic pots," Schulenberg says.
But when she turned to the Iroquois question, Schulenberg again was stymied. Iroquois pots excavated in the 1950s and '60s, as most museum pieces were, had all been carefully washed. The museum pots lacked any trace of carbon residue.
Enter Bill Breen, an amateur archeologist who has been gathering pottery fragments from Kipp Island in Lake Ontario for 50 years. Breen's pots, Schulenberg says, were gloriously dirty, each holding a charred residue up to a millimeter thick. Even better, Breen had fragments of both Point Peninsula and early Iroquois pottery. Schulenberg shipped a selection off to the lab.
"I expected that either the Iroquois pots or the Point Peninsula pots could have shown evidence of corn," she says, "or they both could have." If both did, Schulenberg says, "I could change the conception of the introduction of agriculture in North America. I could prove that the Iroquois were not the first to adopt agriculture in the Northeast after all."
The lab results, however, turned up a fourth possibility: no maize residue at all. None on the Point Peninsula pots, and, surprisingly, none on the Iroquois pots either. "So much for changing the world," Schulenberg jokes. Yet her negative result had accomplished something: "What I've done is show that the models need to be revised.
"My evidence and what it implies is only true for this site," Schulenberg admits. "But ultimately I think that it will help us arrive at a more complicated, more realistic model where we have some agriculture introduced through migration and some developed in place. My goal is to create a more detailed view of how these two peoples interacted." Schulenberg will be examining more residue-laden pots from an Iroquois site in Pennsylvania to flesh out her findings. She will also be creating her own plant residues in the lab, in an effort to refine her still-new technique.
Janet Schulenberg is a Weiss Graduate Scholar in anthropology, 403 Carpenter Building, University Park, PA, 16801; 814-865-0797; jks142@psu.edu. Her adviser, Dean Snow Ph.D., is professor and head of anthropology, 409 Carpenter; 814-865-2509; drs17@psu.edu. Schulenberg's research is funded by the Hill Foundation, the Wenner Gren Foundation, the College of the Liberal Arts, and the Weiss Fellowship. The Weiss Graduate Scholars Fellowships were established with a gift from William L. and Josephine Berry Weiss for the support of interdisciplinary research. Additional reporting by Andrea Messer.