Tracking Viking-assisted dispersal of biodiversity using ancient DNA

The people from Vikings Age Scandinavia are renowned for their overseas voyages over large distances in the North Atlantic. Through trade and agricultural practices these people must have had a strong influence on the biodiversity in the areas where they lived and travelled. The main objective of our project was to investigate the effects of Viking trade and agriculture on the genetic makeup of animals and plants using the latest technological advances in genetic research. Extracting DNA from archaeological plant remains is a great challenge, because the material is typically charred which is detrimental for DNA preservation. We used the latest high-throughput sequencing technology and optimised methods to retrieve DNA from very poorly preserved samples, but all tests showed no DNA was preserved in the charred barley seeds from the Viking Age. Such lack of DNA preservation is an important finding, because the majority of archaeological plant remains are charred. We combined our findings with results on grape, rice and maize from other laboratories and all analyses resulted in the same conclusion: even the latest technology does not yield sufficient genetic data from charred plant remains (published in Scientific Reports in 2017). For the main objective of our project this meant that investigating the legacy of the Vikings on plant diversity using ancient DNA is limited by the lack of well-preserved material, and we are continuing our search for other sources than charred seeds. In archaeological sites animals remains are typically present in the form of bones, and the laboratory protocols to extract DNA from such bones are under continuous development. During this project we developed a new tool to effectively crush bone remains, and a new DNA extraction protocol to maximise the DNA content that can be retrieved (published in Biotechniques in 2018 and in Molecular Ecology Resources in 2017, respectively). Of the diversity of animals that were used by the Vikings, horses were certain one of great importance and their bones have been found throughout the Viking territories. We extracted DNA from over 100 horse bones and found DNA preservation varied from 0 to ~70% with many being very poorly preserved. We developed a hybridisation capture array to increase the information content that we can retrieve from the specimens. Using this data we can show how Viking Age horses are related to the modern breeds we see today, and formulate hypotheses on the establishment of horse populations in the different places where the Vikings settled. By analyzing specific genetic variants, we can also get more insights into certain morphological (e.g. size) or physiological traits of horses buried in high profile sites such as the Oseberg and Gokstad ship burials, and with that improve our understanding of the cultural background of such sites. This work is still in progress and is expected to be published in the scientific literature later this year. Finally, we have extended a simple and cost-effective method to sex biological remains, and used this to successfully sex the largest collection of Viking Age Icelandic horses studied to date. Horses are the most common grave good in Icelandic Viking Age burials, and our results showed a significant bias towards the use of male horses in burial sites compared to non-burial sites. This simple, cost-effective method to reliably sex animal remains even with poor DNA preservation is widely applicable to other animals remains, and the study was published in the Journal of Archaeological Science. In addition to agriculture, trade was a key aspect of Viking culture. The extent of historic trade of natural resources is difficult to assess using archaeological methods alone. In this project we used ancient DNA methods to investigate of two prime marine species, the Atlantic cod and Atlantic walrus. In the first study, we used ancient DNA to identify the biological source of ancient fish bones from several archaeological excavations, including the world-renowned Viking Age site Haithabu. Our results showed that these fish were not locally caught, but instead were obtained from northern Norway and transported over long distances. These findings indicate that the remote resources of the Arctic ocean were already exploited during the Viking Age (published in PNAS in 2017). In the second study, we applied similar methods to traced the biological origin of walrus bones from Europe, Svalbard, and Greenland, covering the entire period of the Greenland Norse occupation. The results showed a significant shift in walrus trade from an early, predominantly eastern source towards a near exclusive representation of Greenland ivory (published in the Proceedings of the Royal Society of London: Biological Sciences in 2018). This study forms an important contribution to the high-profile debate on the history of Atlantic walrus exploitation during the Viking and early medieval period.

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Humans have affected global biodiversity since prehistoric times, greatly altering landscapes and species compositions in areas where they settled. Nevertheless, it is difficult to directly assess the evolutionary impacts of past modifications, as traditi onal archeological approaches are limited in scope for a thorough understanding of biological processes. Here, we investigate the effects of human-driven modification during the Viking Age, a period in which the highly mobile people of Scandinavia coloniz ed regions throughout the North Atlantic, and when extensive trade and agricultural practices promoted the transport and exchange of many species. Specifically, we exploit the latest technological advances in ancient DNA research and high throughput seque ncing to directly investigate relatedness and patterns of functional genomic variation in unique archeological material. We focus on species of great agricultural, cultural and industrial importance (horse, flax and barley) for which excellent genomic too ls have recently been developed. The analysis of whole genome variation will enable us to elucidate demographic processes, characterize the distribution of functional biological variation in the Viking Age, and identify their evolutionary heritage in cont emporary populations. This approach allows us to answer specific archeological questions related to the cultural use of plants and animals, and provides an understanding of the evolutionary processes that accompany human-driven dispersal and domestication . Overall, the combination of the latest genomic technology and material of distinctive cultural and historical value will yield unparalleled insights in Viking archaeology while simultaneously assessing the impact of these people on biodiversity in Scand inavia and surrounding territories.