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DNA samples reveal Viking Age fish trade

It has been assumed that the Vikings were trading in cod, but so far solid evidence has been lacking. With new methods, it is possible to extract ancient DNA from fishbone remnants and this can provide some exciting new information!

The jaw bone of a cod used for DNA extraction – photo courtesy University of Oslo

Towards the end of the 8th century the Viking chieftain Ottar (Ohthere), from Hålogaland in northern Norway, was visiting Haithabu in todays Germany. He brought furs and walrus ivory, that he delivered as gifts to King Alfred the Great of Wessex. The meeting between Ottar and King Alfred is written in ”Historia ecclesiastica gentis Anglorum”, and this is also the text where Norway is mentioned for the first time in history.

Ottar tells King Alfred about his travels and his visit to Haithabu on the way to Wessex. Such historical accounts have provided tantalising ideas about possible early movement of goods from Northern Norway to central Europe, but scientific evidence was inconclusive. Now scientists have been able to use DNA preserved in old fish bones to solve this question.

Researches from the universities of Cambridge and Oslo, and the Centre for Baltic and Scandinavian Archaeology in Schleswig, used ancient DNA extracted from the remnants of Viking-age fish suppers. The study analysed five cod bones dating from between 800 and 1066 AD found in the mud of the former wharves of Haithabu, which was an early medieval trading port on the Baltic.

The DNA from these cod bones contained genetic signatures seen in the Arctic stock that swims off the coast of Lofoten: the northern archipelago still a centre for Norway’s fishing industry.

Researchers say the findings show that supplies of ‘stockfish’ – an ancient dried cod dish popular to this day – were transported over a thousand miles from northern Norway to the Baltic Sea during the Viking era.

Prior to the latest study, there was no archaeological or historical proof of a European stockfish trade before the 12th century.

Norway’s first export?

“It has long been speculated that the trade of Norwegian stockfish might have begun in the Viking Age (i.e. 800-1066),” says Dr. James Barrett of the University of Cambridge, “but this interpretation has been controversial because the earliest definite historical evidence dates from the 12th century and previously the most secure archaeological evidence had been from the 13th century. Past research at Cambridge using stable isotopes strongly suggested that the Haithabu cod were not from local waters, but we could not say for certain where they had been caught.

“With the new ancient DNA evidence we now know, with a high degree of confidence that they were from Arctic Norwegian cod. If the bones are from 1066 (their latest possible date) we have only changed existing knowledge a little, but it is equally likely that they are from the 9th or 10th century, in which case our understanding of Viking Age trade might need to be rewritten.

“This trade may have been as much about staple commodities as about luxury goods, such as walrus ivory or furs. Having opened this possibility, we aim to investigate more precisely dated cod bones in the future, at Haithabu itself or other sites in the region, and that more bones can be analysed in order to evaluate the scale of this activity. Do the bones only represent travelling provisions, or are we witnessing urban provisioning over vast distances?”

The sequencing of the ancient cod genomes was done at the University of Oslo, where researchers are studying the genetic makeup of Atlantic cod in an effort to unpick the anthropogenic impacts on these long-exploited fish populations.

“Fishing, particularly of cod, has been of central importance for the settlement of Norway for thousands of years. By combining fishing in winter with farming in summer, whole areas of northern Norway could be settled in a more reliable manner,” says the University of Oslo’s Bastiaan Star, another author of the new study.

Sanne Boessenkool and Bastaan Star are working on ancient DNA samples – photo courtesy University of Oslo

In order to be certain of where the fish were from, Bastiaan Star and Sanne Boessenkool, who work at the work at the Centre for Ecological and Evolutionary Synthesis (CEES), compared the genetic profiles from the old bones to those from modern cod populations from the same areas. Although it is too early to identify specific mutations and changes in the DNA that may have happened over time, these profiles were detailed enough to pinpoint the most likely source population back in time. Such comparisons can tell us a lot about human and animal development over time and give us a better understanding of evolution.

Even if we do not know if the cod in Haithabu represent travellers provisions or that they were goods for trade, it is quite certain that the cod did not end up there by itself. With these advanced methods we can learn more about Ottar from Hålogaland and how he lived.

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