To bolster that notion, Naumann and her colleagues analyzed the skeletons' mitochondrial DNA, which is passed on through the maternal line. The team found that bodies buried together were most likely not related, at least on the maternal side.
Next, they analyzed the ratio of carbon and nitrogen isotopes, or elements with different molecular weights, in the bones of the ancient Scandinavians.
Because food that comes from the sea or the land contains different proportions of heavy and light isotopes of carbon and nitrogen, the concentration of these chemicals in bones can reveal the dietary history of a people.
Results showed the beheaded people ate more fish protein, whereas the others ate land-based protein sources, such as meat and dairy products. That suggests the people buried together came from very different strata of society.
Naumann proposes the beheaded victims were slaves who were sacrificed as gifts to be offered in death on behalf of their masters. Though such human sacrifice was uncommon in Viking society, it wasn't unknown.
"There are other examples of sacrifice in burials, where individuals had tied hands and feet and were sometimes beheaded, or in other ways treated in ways that indicates sacrifice," Naumann said. "It is assumed that such persons were grave gifts, and would follow their masters in death. One historical account from Ibn Fadlan (an Arab traveler who chronicled his journeys) describes how a slave woman volunteered to follow her master — a Viking chieftain — in the grave."
The find will be detailed in a forthcoming issue of the Journal of Archaeological Science.
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