Chemical and isotopic examination of copper artefacts from southern Africa uncovers unexpected cultural linkages among people living in the region between the 5th and 20th centuries according to a University of Missouri researcher and colleagues.
The paper appears in the PLOS ONE publication.
According to Jay Stephens, a post-doctoral fellow in the MU Research Reactor (MURR) Archaeometry Lab, people in the area between northern South Africa and the Copperbelt region in central Africa were more interconnected than previously imagined.
The majority of archaeologists have, he continued, “framed the archaeological record of southern Africa in a global sense over the previous 20 to 30 years, with a strong focus on its connection to imports arriving from the Indian Ocean.” The data reveals that interactions between the various groups of people living in southern Africa included not only the movement of goods but also information flows and the sharing of technological practises that go along with those exchanges. However, it’s also crucial to acknowledge the interconnected relationships that existed between these groups.
With the archaeological record, “we now have physical ties to rebuild connectivity at various moments in time,” the man added. “There is a massive history of interconnectivity found throughout the region in areas now known as the countries of Zambia, Zimbabwe and the Democratic Republic of the Congo. This also includes people from the contemporary Ingombe Ilede, Harare, and Musengezi traditions of northern Zimbabwe between at least the 14th and 18th centuries A.D.”
Little samples from 33 copper ingots were taken by researchers, who then studied them at the University of Arizona to get at their conclusions. Researchers carefully chose each sample from the archaeological samples they discovered in the collections of the Livingstone Museum in Livingstone, Zambia, and the Museum of Human Sciences in Harare, Zimbabwe.
“We didn’t want to damage the exhibition of an object, so we attempted to be cognizant of how museums and institutions would want to interact with the data we collected and share it with the broader public,” Stephens said. “We also want our information to be accessible for the folks in these communities who continue to connect with these items. Ideally, some of the skills linked with these studies can be used by anyone wants to ask similar questions in the future.”
Stephens said copper ingots are good artefacts for this type of examination because they frequently have symbolic shapes that allow archaeologists to identify specific markings and follow changes throughout different time periods.
“By looking at their changes in structure and morphology across time, we can match those changes with how technology improved over time,” he said. “This frequently comes from observing the decorative details formed by the cast object or mould, or other surface properties seen on these things.”
Once the samples arrived at the University of Arizona lab, researchers collected a small bit of each sample—less than one gram—and dissolved it with certain acids to leave behind a liquid combination of chemical ions. Afterwards the samples were examined for lead isotopes and other chemical components. Lack of available data to compare their samples with was one issue the researchers ran against.
In order to build a solid data set, Stephens said, “one component of the study involves evaluating hundreds of ore samples from different geological deposits in southern Africa—especially ones extracted before the entrance of European colonial powers. “The data can give a scientific foundation to assist back up the inferences and conclusions we make in the study.”
