Greenland Vikings Killed Too Many Walruses to Stay There, Study Suggests

The collapse of Greenland's Nordic colonies and the unexplained disappearance of the Vikings who lived there is one of history's big mysteries. Now, a paper published in Quaternary Science Reviews suggests it may (at least partly) have been triggered by the over-exploitation of the community's most prized resource—walrus tusk.

Walrus ivory was traded up and down Europe in the early Medieval period, when it was considered a hot commodity. The material was used in objects from crucifixes to game pieces, and Greenland's Norse settlements held a "near monopoly" on the product.

But after a period of success, Europe's hunger for walrus ivory may have caused the community's downfall. Analysis of ivory products from the period suggest the traders increasingly relied on smaller, frequently female animals from regions further north. That would have meant a longer and more dangerous journey. Often for a smaller reward.

"Norse Greenlanders needed to trade with Europe for iron and timber, and had mainly walrus products to export in exchange," lead author James H. Barrett from the University of Cambridge's Department of Archaeology said in a statement.

"We suspect that decreasing values of walrus ivory in Europe meant more and more tusks were harvested to keep the Greenland colonies economically viable."

Norse colony
Church ruins from Norse Greenland's Eastern Settlement. The Norse mysteriously disappeared in the fifteenth century and overexploitation of walrus may help explain why. James H. Barrett

An international team of researchers from the U.K. and Norway analyzed 67 pieces of rostrum that date back to the 11th and 15th century. (The rostrum is the skull and snout that the tusk remains attached to in shipment.) A combination of ancient DNA and stable isotopes were used to determine the sex and geography of the animal.

The team also considered trends in manufacturing techniques that can indicate when the bone was used.

The results of that analysis suggest a shift to animals from an evolutionary branch of walrus predominantly found in the area around Baffin Bay, in the northwest of the country. This theory is supported by the presence of Norse artefacts among the remains of 13th and 14th century Inuit settlements, the researchers say.

The analysis also appears to imply a growing dependency on smaller, female animals, when the larger tusks of male walruses were likely to have been preferred. A higher ratio of females suggests there was a strain on resources, most likely caused by the over-exploitation of walrus populations—though medieval climate change (the "Little Ice Age") may also have played a part.

Venturing up north would have been more treacherous and provided the Norse people with a shorter hunting season given the abundance of ice.

As the supply chain dwindled, there appeared to be a growing preference on mainland Europe for elephant tusk, brought via the West African trade routes.

"Despite a significant drop in value, the rostra evidence implies that exploitation of walruses may have even increased during the thirteen and fourteenth centuries," said Barrett.

"As the Greenlanders chased depleted walrus populations ever northwards for less and less return in trade, there must have come a point where it was unsustainable. We believe this 'resource curse' undermined the resilience of the Greenland colonies."

The result was a "perfect storm" of fewer resources and less demand—exacerbated further by climate change, which has long been hypothesized as one of the reasons for the Norse people's disappearance in Greenland in the fifteenth century.

"An overreliance on walrus ivory was not the only factor in Norse Greenland's demise. However, if both the population and price of walrus started to tumble, it must have badly undermined the resilience of the settlements," co-author Bastiaan Star of the University of Oslo said in a statement. "Our study suggests the writing was on the wall."

An elaborately carved ecclesiastical walrus ivory plaque from the beginning of the medieval walrus ivory trade, featuring the figure of Christ, together with St. Mary and St. Peter, and believed to date from the 10th or 11th century. Museum of Archaeology and Anthropology, University of Cambridge.