Radiocarbon dating techniques re-setting Indigenous histories

A session organized by UGA faculty at the Society for American Archaeology Meetings in early May discussed the ways recent innovations in radiocarbon dating are rewriting the history of Indigenous sites. 

Many of these new histories are challenging conventional wisdom about Indigenous persistence, or the lack thereof, in the face of European contact, researchers reported during a session co-organized by Jennifer Birch, professor of anthropology, and reported in Science:

Traditionally, archaeologists have subdivided the history of eastern North American sites based on shifting ceramic styles, as well as the presence or absence of European artifacts. If a site contains objects such as iron blades or glass beads, archaeologists include it in the so-called “historic” period, placing it earlier or later depending on the number of European artifacts. If a site lacks such items, researchers assume it was occupied in the precontact era.

“A lot of us are really frustrated by this arbitrary division of time,” says Michelle Pigott, an archaeologist at the University of Tennessee, Knoxville. But in colonial eastern North America, it was often the best archaeologists could do. Radiocarbon dating during this time frame is particularly tricky.

The method works by measuring levels of carbon-14 in organic material such as wood, charcoal, and seeds. Living things absorb the radioactive isotope from the atmosphere, and it gradually decays after death. But turning carbon-14 levels into an age expressed in calendar years requires knowing how much radiocarbon was in the atmosphere when the wood or seed was alive. That baseline fluctuates over time—sometimes substantially, as it did during the 15th through the 17th centuries. For that period, radiocarbon dating can yield possible calendar years that are “wildly different but all completely plausible,” says Jacob Holland-Lulewicz, an archaeologist at Pennsylvania State University, resulting in uncertainties of a century or more.

The new dates are helping answer questions tribal nations have about their own history. Victor Thompson, an archaeologist at UGA, is redating sites in Georgia’s Ocmulgee Mounds National Historical Park at the request of the Muscogee (Creek) Nation, whose citizens lived in the region until they were forcibly removed by the U.S. government to Oklahoma in the 19th century. Thompson presented unpublished data showing the Lamar site in Ocmulgee was very likely the Indigenous town known as Ichisi that was visited by Spanish explorer Hernando De Soto in 1540.

Birch and Thompson were joined in the symposium by several UGA faculty and alumni, including Megan Conger, Center for Applied Isotope Studies; Brita Lorentzen, Anthropology and Tree Rings and Archaeological Wood Laboratory; Seungyeon Hong (RA), Anthropology and Tree Rings and Archaeological Wood Laboratory; and Mark Williams (Emeritus), Anthropology and Laboratory of Archaeology, UGA.

UGA alumni at the session were co-organizer Stefan Brannan (MS Archaeological Resource Management '09, PhD Anthropology '18) of New South Associates; Jake Holland-Lulewiscz (PhD Anthropology '18), assistant professor, Penn State University; and Brandon Ritchison (PhD Anthropology '19), assistant professor, University of Illinois Urbana-Champaign.

"By homing in on when key events and processes transpired in early colonial eastern North America, participant in the session revealed how complex and variable Indigenous responses to European incursions were," Birch said. "This included the relatively rapid reconfiguration of social landscapes as well as the persistence of cultural practices for more than a century after those initial encounters. Clearly, we have much more to learn." 

Participants in the session will reconvene at UGA in fall 2025 for a research seminar sponsored by the Willson Center for Humanities and Arts. 

Image: Ocmulgee Mounds National Historical Park. – ROBERT RAUSCH/THE NEW YORK TIMES VIA REDUX