UNIVERSITY PARK, Pa. — For more than a decade, Thomas Harper, adjunct lecturer in Penn State’s Department of Anthropology, has collaborated with colleagues in Ukraine to examine the movements of prehistoric agricultural communities across Eastern Europe.

Recently, the group shed new light on that timeframe with radiocarbon measurements made by the accelerator mass spectrometer (AMS) in the Radiocarbon Laboratory of Penn State’s Institute of Energy and the Environment. They published their findings in Radiocarbon, a publication of Cambridge University Press.

“What really interested us was how archaeological cultures move across the landscape, and how this corresponds with people moving and establishing settlements at the time,” co-corresponding author Harper said. “In central Ukraine, almost all the people had been hunter-gatherers until that point in time. With the movement of pottery and other materials into the region, we can see the establishment of the first agricultural communities in the area. They’re practicing farming, but when you move farther east, they’re practicing herding and hunting and gathering.”

The researchers set out to resolve long-unanswered questions about the chronology of the settlements by examining the elaborately decorated clay pottery found at the archaeological sites, and through high-precision AMS radiocarbon dating of the bones of domesticated animals including sheep, goats, pigs and cattle. Living organisms take in radiocarbon — or carbon 14 —from their exposure to environmental carbon dioxide. After death, carbon 14 begins to decay at a consistent rate. The AMS can efficiently measure how much carbon 14 a specimen contains, and researchers can then determine how long the carbon 14 has decayed, aging the specimen with precise accuracy.  

“In Ukraine, it’s an interesting environmental context,” Harper said. “Going from east to west, you have the steppe, which is this vast grassland, but then you have the forest-steppe, which is kind of a transitional zone, and then you have the Eastern European Forest. There were different sorts of strategies employed by people to survive in different regions. It’s the very periphery of what archaeologists call ‘Old Europe,’ these Neolithic societies where people were subsisting off agriculture. By looking at the movement of these settlements, we’re seeing how these people were extending the edge of this periphery over time eastward.”

Harper and his colleagues focused a portion of their research on the Eastern Tripolye Culture, a sub-group of Cucuteni-Tripolye people who from about 4300 to 2950 B.C. expanded into the forest-steppe region of Central Ukraine. Current scholarship suggests, Harpers said, that Neolithic and Copper Age systems of settlement and subsistence in Eastern Europe were defined by short-to-medium range migration, while sparsely populated land in peripheral regions allowed for the continual colonization of new territories.

The group dated materials from eight Eastern Tripolye sites. Through those tests, they were able to revise the chronology of two phases of its development: Tripolye BI and BI-II. Rather than consisting of distinct “early” and “late” time periods, the researchers found they instead constitute a single period in which the material culture had a range of stylistic diversity.

Once the chronology was clearly established, the researchers then analyzed the space-time distribution of sites, which revealed a southwest-to-northeast migratory vector across Central Ukraine marked by episodes of what Harper and co-corresponding author Aleksandr Diachenko refer to as “leapfrog” colonization. Through that, the group determined that the sites established by the Eastern Tripolye Culture mostly predated the larger-scale population movements by the Western Tripolye Culture during the first part of the 4th millennium BC, which established the largest settlements of prehistoric Europe.

“The project outcomes significantly improve our understanding of the evolution of Neolithic communities in Southeastern Europe, mutual interactions between various population groups, transfer of technological knowledge and styles,” said Diachenko, who is a researcher with the Institute of Archaeology of the National Academy of Sciences of Ukraine. “Work on all these topics requires the development of fine-grained chronologies, and the project’s success was grounded on integrating relative chronologies based on the analysis of pottery styles and absolute dating. The extremely good quality of the AMS dates obtained in Penn State’s Radiocarbon Laboratory made possible a solid chronological framework for our deep understanding of prehistoric Neo-Eneolithic Europe and further mutual collaboration between scholars from the U.S., Ukraine, Republic of Moldova, Romania and Poland.”

A specialist in demographic archaeology and radiocarbon dating, Harper has worked on the project since forming a close collaboration with Diachenko at the University at Buffalo, State University of New York, where Harper received his doctorate and Diachenko served as a Fulbright Visiting Scholar. A grant from the National Science Foundation allowed Harper to pursue his postdoctoral research at Penn State in 2017 and 2018, which involved dating a large quantity of prehistoric materials from Ukraine.

“Previous radiometric, or older style, radiocarbon dates in the region caused many interpretive problems for Ukrainian archaeologists, who had pieced together the general sequence of sites but did not know their absolute dates,” Harper said. “What Penn State’s involvement brought to the picture was advanced analysis and being able to run these dates internally. We could generate AMS dates for not a whole lot of money and target them for high impact. And the great thing about working with our Ukrainian partners is that they have a history of 120 years working with these materials. We go through the old literature, and the research questions are there. So, we’re not reinventing the wheel, but coming in as equal partners.”

Harper said the group next plans to produce additional papers on other Cucuteni-Tripolye sites in Southwestern Ukraine and Moldova. He said he’d eventually like to return to Ukraine, although that timeline remains uncertain as Ukraine’s war with Russia continues well into its second year. Archaeological research continues in Ukraine, although several of Harper’s colleagues are fighting in defense of the country.

“There’s really no end to the type of questions that can be asked — we’re just scratching the surface,” Harper said. “Our revised chronologies are now being taken up by people in Ukraine, and things are starting to make more sense. On a personal and professional level, it’s opened up a lot of opportunities for partnerships between us and the National Academy of Sciences of Ukraine, and it’s generated a lot of goodwill and trust. Despite the geopolitical landscape, our collaborations continue. I’ve made a lot of great friends in Ukraine.”

In addition to Harper and Diachenko, paper co-authors include Douglas Kennett, a former Penn State faculty member now at the University of California, Santa Barbara; Laurie Eccles, research technologist in the Penn State Department of Anthropology; and Sergei Ryzhov, Yuri Rassamakin and Elena Tsvek from the Institute of Archaeology of the National Academy of Sciences of Ukraine.