Ancient DNA reveals the extent of Norse Greenland’s trade in walrus ivory
Norwegian and British researchers have analysed DNA from up to 1100 year old walrus remains and confirmed that walrus ivory was a driver for both the success and decline of the old Norse colony of Greenland. They also revealed the shifting patterns of walrus ivory trade in medieval Europe and found traces of a major evolutionary split in the Atlantic walrus population.
The Vikings were Norse seafarers who raided and traded across wide areas of Europe during the late 8th to 11th centuries, even settling in areas of Greenland.
Remains of the animal and plant materials they used and traded are often found in archaeological excavations. Advances in DNA technology have made it possible to analyse ancient DNA in some of these remains.
In 2014, the Research Council of Norway funded an Oslo-led project named Tracking Viking-assisted dispersal of biodiversity using ancient DNA. At approximately the same time, the Leverhulme Trust in the UK funded a Cambridge-led archaeology project on medieval Arctic trade called Northern Journeys.
These projects combined forces and have used ancient DNA to uncover new stories about the Viking Age ever since. One of these stories came out in 2017, when the researchers showed that cod remnants found in Viking Age Haithabu (Germany) were brought all the way from the Lofoten Islands in Norway.
Several discoveries from ancient DNA
Also this time, biologists from UiO have cooperated with archaeologist James H. Barrett at the University of Cambridge. Together, they have analysed and interpreted DNA samples extracted from walrus skulls and tusks – most dated between 900 and 1400 CE – found in museums in Bergen, Oslo, Trondheim, Copenhagen, Dublin, Le Mans, London, Schleswig and Sigtuna.
These results have uncovered novel information about the natural history of the Atlantic walrus and have also revealed patterns of trade in walrus ivory in Europe during the Middle Ages.
These findings provide a new economic understanding of the Norse settlements on Greenland.
“We knew from the start that analysing ancient DNA would have the potential for new historical insights. But the results from analysing DNA in walrus skulls and tusks proved to be particularly spectacular. Looking at ancient DNA is a very valuable tool for both biologists and archaeologists”, senior author Sanne Boessenkool at UiO comments.
The Norse settlements on Greenland
As most Norwegian and Icelandic schoolchildren know, explorers led by Erik the Red set out from Iceland and reached the southwest coast of Greenland in the 980s. The ensuing Norse settlements on Greenland lasted almost 500 years and consisted of emigrants from Norway and Iceland.
Archaeologists and historians have long speculated that the trade in walrus ivory played an important role in the success of the Norse colony of Greenland, and that the end of the trade may have led to its collapse.
Before the project started, the researchers already knew that walrus products could have come from different regions in the Arctic. An eastern source, from the Barents Sea region, was documented as early as the late 9th century CE, when the chieftain Ohthere (Ottar) of Hålogaland visited the court of King Alfred of Wessex in England. The meeting between Ottar and Alfred was described in a contemporary document where Arctic Norway is mentioned for the first time in historical records.
Later, the transport of walrus products – ivory, hide ropes and even a decorated walrus skull – from Greenland to Europe as gifts, tithes and trade goods is described in historical sources dating from the 13th and 14th centuries. But before DNA analyses, it was impossible to know the relative importance of these sources during the centuries of Norse settlement in Greenland.
“Until now, there was no quantitative data to support the story about walrus ivory from Greenland. Walruses could also have been hunted in the north of Russia, and perhaps even in Finnmark, in Norway at that time. Some may also have come from Iceland. But our research proves beyond doubt that much of the ivory traded to Europe during the Middle Ages really did come from Greenland”, explains first author Bastiaan Star.
Bastiaan Star and Sanne Boessenkool both work at the Centre for Ecological and Evolutionary Synthesis (CEES), Institute for Biosciences, University of Oslo. This is where the UiO's ancient DNA-laboratory is located and managed.
Shifting patterns of trade
The researchers have been able to establish the biological origin of 23 archaeological specimens from Europe.
“The results suggest that by the 1100s CE Greenland had become the main supplier of walrus ivory to Europe. Our study provides empirical evidence for how its small and far flung community was integrated into a medieval and pan-European network”, explains James H. Barrett from the Department of Archaeology at the University of Cambridge.
Between the settlement of Greenland in the 980s and the 1100s, when the Norse settlement on Greenland was in its infancy, the story is less clear. Some ivory may then have arrived in towns such as Sigtuna and Dublin from the Barents Sea region and Iceland, in addition to Greenland.
The DNA evidence could also suggest that inhospitable eastern Greenland was explored at this early stage in the settler’s familiarity with their environment, before the north-western hunting grounds around Disko Bay, well known from later sources, became established.
In the later period between ca 1125 and 1400 CE, however, the DNA shows that most European walrus finds that were analysed derived from western Greenland, and there is a high probability that even all the specimens of this date range were from this region.
A popular material in its own right
Ivory made from walrus tusks has been viewed as a substitute for elephant ivory in the Middle Ages. Barrett doesn’t agree with that assessment.
“During the Romanesque period, especially the 1100s CE, walrus ivory was just what people wanted. At the same time, it wasn’t at all impossible to obtain elephant ivory”, he explains.
Ivory from the Atlantic walrus was certainly a popular material for the manufacture of luxury objects in medieval Europe. A famous example is the Lewis chessmen, which were probably made in Trondheim around 1200 CE and discovered in 1832 on the Isle of Lewis in the Outer Hebrides of Scotland.
Most of the Lewis chessmen are carved from walrus ivory, with a few instead made from whale teeth. Today, 11 pieces are owned and usually exhibited at the National Museum of Scotland in Edinburgh, and the remaining 67 are at the British Museum in London.
What the researchers did
The researchers could obviously not analyse DNA from objects like the Lewis chessmen, because they would have had to damage them in order to extract samples. For this study therefore, they have instead focused on skulls and tusk offcuts, where remnants of DNA can still be found. Walrus tusks were often traded in pairs, still attached to the front part of the animal’s skull.
These skull fragments, often broken in medieval times when the ivory was removed for use, provided ideal material for analysis. Yet walrus skulls are particularly tough, which inspired the researchers to design a mortar in stainless steel and commissioned it from a local craftsman.
The researchers analysed the entire mitogenomes, that is the DNA found in mitochondria, of 37 archaeological walrus specimens found in the European mainland, Svalbard and Greenland.
“We compared our data to 306 modern and 19th century walrus specimens from the Barents Sea region, Greenland and the Canadian Arctic. This was done in order to infer the geographical origin of European walrus imports during the chronology of the Norse occupation of Greenland”, explains Star.
How the Ice Age affected the walrus
However, the ancient DNA had more stories to tell. “The ancient DNA also told us that Atlantic walruses must have consisted of two main breeding populations that separated over 20,000 years ago, probably during major glacial events, such as the last Ice Age”, explains Boessenkool.
When the ice invaded the Atlantic coasts southwards, the walruses were forced to live in two separate regions on either side of the Atlantic. The descendants of the western population can still be found along the coast of Canada and Greenland, while those of the eastern side can be found around Svalbard in Norway, in Russia around the Franz Josef Land archipelago, and also along the Russian coastline of the Barents Sea.
The value of interdisciplinarity
The ancient DNA project has once again demonstrated the value of interdisciplinarity in research. As an archaeologist, it was James H. Barrett’s task to discover and obtain the tusks and skulls of walruses from museums. Scientific assistant Agata T. Gondek at the UiO did most of the extraction of DNA from the material. Sanne Boessenkool and Bastiaan Star focused on sequencing and analysing the DNA.
Finally, Barrett worked on the archaeological interpretations together with the Oslo team. To ensure the success of this interdisciplinary collaboration the team often worked together in practice, on location in museums, in Oslo and remotely by cloud computing.
Read more on Titan.uio.no:
- DNA-samples from the Viking age show that cod remnants in Germany come from Lofoten in Norway
- A stream of surprises from the Atlantic cod genome
- Fossils recount a bustling ocean 100 million years ago
- A threat to cod is a threat to humans
Bastiaan Star, James H. Barrett, Agata T. Gondek and Sanne Boessenkool: Ancient DNA reveals the chronology of walrus ivory from Norse Greenland.
Gondek A.T., Boessenkool S., Star, B. 2018: A stainless-steel mortar, pestle and sleeve design for the efficient fragmentation of ancient bone. Biotechniques doi: 10.2144/btn-2018-0008
Bastiaan Star, Sanne Boessenkool, Agata T. Gondek, Elena A. Nikulina, Anne Karin Hufthammer, Christophe Pampoulie, Halvor Knutsen, Carl André, Heidi M. Nistelberger, Jan Dierking, Christoph Petereit, Dirk Heinrich, Kjetill S. Jakobsen, Nils Chr. Stenseth, Sissel Jentoft, and James H. Barrett: Ancient DNA reveals the Arctic origin of Viking Age cod from Haithabu, Germany. PNAS, August 7, 2017.
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