By Pat Lowinger
In 1953, James Watson and Francis Crick published their first paper of what was to become the first of many in a series in the emerging field of molecular biology, The Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid (DNA). Building upon this monumental discovery, science has, over the past seventy years had continued to examine, catalog and ultimately sequence the DNA of over sixty thousand plant and animal species. In regards to humans, this technology has allowed for the testing and diagnosis of numerous genetic diseases, genetic inheritance patters and questions of paternity. In the past two decades, there has been an increased use of genetic material in the examination of human migration patterns. One powerful technique which has been utilized is the ‘finger-printing’ of mitochondrial DNA (mtDNA) sometimes referred to as maternal DNA for reasons which will be fully examined throughout this narrative. By using a variety of recently pioneered techniques mtDNA can now be extracted from the remains of long dead persons and be compositely analyzed to an ever growing list of regional and ethnic genomic markers. In light of this new technology and recent archaeological discoveries it is necessary to reexamine the impact of Scandinavian migrations to the British Isles, but also dispel long-held and often dogmatic historical narratives which are very often perpetuated in the historiography of the British Isles and their closely related neighbor, Iceland. Often mis-characterized as being solely motivated by plunder and military conquest, the Scandinavian migrations during the late Eighth through Eleventh Centuries AD were in fact a complex series of migration events, at times characterized by raiding, military conquest, in order to establish colonies throughout the British Isles by Scandinavian settlers.
The Scandinavians were relative newcomers to the British Isles during the late Eighth and Ninth Centuries AD- having come after both the Saxons (Late Fourth through Fifth Centuries AD) and the Romans (First through Fourth Centuries AD). But both Romans and Saxons appear to have settled to the southern portion of Britain. For the Romans, Hadrian’ Wall is generally accepted to mark the point of Roman expansion, while for the Saxons, conquest and settlements appear to have been concentrated along the Saxon Shore.
The year 789 AD holds dubious distinction in English history, as it was the first known (and recorded) hostile action between Scandinavian raiders (Vikings) and the people of Portland (in Dorset). This relatively small band of 3 Norwegian longships (misidentified as Danish by English chroniclers) arrived, possibly for the purpose of trade, instead murdered the Reeve for unknown reasons and subsequently looted the town. English chroniclers would continue to note intermittent Viking raids of towns and monasteries along Britain’s northern coast for the until the mid 850’s AD.
In 865 AD, the first large Scandinavian ‘army’ (commonly known as the Great Heathen Army) landed in East Anglia and soon captured the city of York. Following these initially successes, additional Scandinavians arrived and settled along Britain’s eastern coast. By 878 AD, the Scandinavians had conquered sizable holdings of east and central Britain- including the cities of York, Leicester and London. In 884 AD, the Scandinavians (predominately Danes) and Anglo-Saxons established what is now commonly referred to as the ‘Danelaw’– the region which allowed for Danish self-rule in territories previously under Anglo-Saxon control. As noted in the Anglo-Saxon Chronicle, “The same year  Healfden divided the land of the Northumbrians; so that they became afterwards their harrowers and plowers.” While brief, this entry indicated a significant investment by the Scandinavians into developing newly acquired agricultural holdings for long-term investiture. The Scandinavian migration and settlement was not only limited to the eastern coast of Britain, but was also significant in Ireland, Scotland, Iceland, Normandy and the Baltic region.
Fundamentals of mtDNA Technology and Inheritance
DNA within animal cells, such as Homo sapiens is normally categorized into two broad types. The first type in commonly referred to as intra-nuclear which is associated with the formation of chromosomes. Chromosomes are the key loci of genetic information within a human cell, containing a complete copy of all of the genetic material and coding(s) necessary for the development of cells, tissues and organs. In effect, most eukaryotic cells (animal cells) contain a complete copy of all of the genetic information of their parent organism, thus a single leukocyte (white blood cell) or follicular stem cells (hair growing cells) can be utilized to examine the entire genetic profile of the organism from which they originated. As the products of sexual reproduction, an individual Homo sapiens genetic profile is in fact a complex hybridization of the DNA received from their parents. In the case of humans, a male sperm carries 23 single chromosomes which will fertilize a female egg cell- which also contains 23 single chromosomes. Together, each of these 23 single chromosomes ‘pair-up’ to form a single cell containing 23 pairs of chromosomes and a diploid cell (which is what a typical human eukaryotic cell is).
While the overwhelming amount of genetic material is located within the nucleus, there is a small amount (less than 0.25 %) to be found outside, or extra-nuclear. This extra-nuclear DNA is associated with small, self- replicating organelles, know as mitochondria. Mitochondria are responsible for the conversion of glucose into ATP (adenosine triphosphate) which powers the metabolism of the cell- often referred to as the ‘power house’ of the cell. Mitochondria are unique not only because they produce energy within the cell, but that they self-replicate via their own DNA which is stored within their own structures. To distinguish mitochondrial DNA from cellular DNA, the prefix ‘mt’ is added. These relatively small pieces of mtDNA contain nearly 17,000 base pairs and code for 37 different genes which has been fully sequenced (and mapped) by geneticists.
Like DNA, mtDNA undergoes point mutations leading to genetic drift- or more simply genetic drift within the human species. These mutations, unless immediately fatal are occasionally conserved within the host organism and passed along to its progeny, with one notable exception which will bed addressed at greater length shortly. So, just as there are DNA markers (genes or more precisely sets of genes) which code for various hair and eye colors, there are mtDNA markers and mutations which can be readily identified by modern biotechnology. And as with phenotypic expressions of hair and eye color, DNA markers can be utilized to identify regional or ethnic origins- such as the use of haplogroup R1b to identify those of Ashkenazi Jewish ancestry. The same kind of markers in mtDNA can be utilized to identify regional and/or ethnic groups, yet unlike DNA, mtDNA mutations or variations do not manifest in visibly different characteristics between two groups (such as hair and eye color).
In addition, mtDNA is not transferred by the male during sexual reproduction. The mother’s egg supplies all of the cells (ovum) mitochondria for the soon to develop fetus. Thus all of the mtDNA contained within successive progeny can be traced entirely through matriarchal lines. Thus by process of ‘genetic subtraction’ it is possible to determine if subsequent offspring arose from distant and distinct parentages in the remote past.
The Scandinavian Settlers of Britain
Those Scandinavians who came in the wake of the great military invasion(s) of 865 AD were made up not only of able bodied men and youths of military age, but also a moderate to high percentage of women. Previously suggested models of Scandinavian migration theory have postulated that the majority of Scandinavian settlers were men, who often intermarried with Anglo-Saxon women as suggested the all too often repeated narrative of widespread Viking raiding, pillaging and raping throughout the areas of Britain which they had conquered. While forced sexual relations by Viking conquerors upon the native Anglo-Saxon population can not be fully dismissed, the extremely low frequency and detection of non-Scandinavian mtDNA suggests such copulation was rather rare prior the end of the Tenth Century AD. This further supports assertions that newly constructed Scandinavian settlements remained largely isolated from their Anglo-Saxon neighbors, even within the Danelaw region. The earlier established and accepted theory regarding Scandinavian migration patterns were based largely upon written source materials and the examination of known Scandinavian graves and burial mounds. Recent examination and DNA analysis of female Scandinavian remains, dated between the Ninth and Eleventh Centuries AD indicate the migrating population consisted of no less than one-third of women and was as possibly high as forty percent.
Knowing what percentage of the Scandinavian migrants to Britain were female brings us no closer to a positive cultural identification of the Scandinavians themselves. Where they all Danish and/or Norwegian? It has been the long standing limitation that identification of the origins of various Scandinavian migrants were based on their point of demarcation to Britain or the particular king or warlord they traveled or settled under. By examining the remains (and their DNA) of known Vikings who immigrated during the Ninth through Eleventh Centuries, it becomes immediately clear that Scandinavian migrants to Britain were an ethnically diverse group. While most Scandinavian migrants did originate from known Scandinavian countries- a small, but notable percentage bear genetic markers which showed origins in Baltic Europe, South-western Russia and Northern Ireland.
What these rather small groups show us is that Scandinavian settlers from other areas, such as the Baltic or Ireland first immigrated to those areas were some level of intermarrying occurred, followed then by subsequent immigration and settlement within the Danelaw region- commonly referred to as ‘second generation’ migrations. This information presents several new questions which remain largely unanswered; what forces drove these particular Scandinavians from their recently settled homelands to the eastern coast of England? what where the political or social pressures which inspired renewed settlement efforts within the Danelaw? It is possible that a decisive answer may never be obtained, but in light of the strong archaeological and genetic evidence, the Danelaw region was experiencing a significant influx of settlers apparently intent upon establishing permanent residence.
The Huxley and Surrounding Viking Hoards
In 2004, a Scandinavian hoard was discovered in Northwest England (Huxley), dated to around the year 900 AD. The relative size and wealth contained within the hoard suggests a growing importance of the settlement in regards to its position between Dublin, the Irish Sea and the northern Danelaw. To date there have been three Viking hoards found in the Cheshire region; Huxley, Eccleston and the so-called ‘coin hoard’ at Chester. Of the armbands (arm rings) found at Huxley, many contain features which are classified as Hiberno-Scandinavian, being of mixed Irish and Scandinavian cultural and artistic influences. Two plausible explanations for the hoards existence in this region: The first is that these items belonged to Scandinavian settlers who had been forced to flee or otherwise migrate to the Danelaw from Dublin. The second possibility is that the items were created locally, by Hiberno-Scandinavians who had settled in the region. Whichever is the case, it demonstrates the transitory nature of Scandinavian settlers, who resettled as needs and/or desires prompted them to.
The high number of silver coins found at Chester demonstrates that by the 920’s the minting of coinage by the Scandinavians was widespread- occurring at Lincoln and Rochester in addition to York. In addition to the locally minted coins, there were a significant number of imported coins- namely southern England. The Danelaw, consisting to two independent kingdoms; Northumbria and East Anglia appears to have regarded the coinage of the other as foreign, demonstrating the relative disconnect of authority (or submission) between the two respective powers within the Danelaw. It is also interesting to observe that coins minted after Guthrum’s (christened as Aethelstan) conversion to Christianity in 878 AD contain the obvious Christian iconography of the cross. While Scandinavians living in the areas of the northern Danelaw remained largely pagan, the conversion of Guthrum and several of his key chieftains marked a significant shift culturally among these early Scandinavian settlers, which in many ways brought them culturally and politically closer to the Anglo-Saxons living within and outside the southern Danelaw region. Thus further suggests that the Danelaw was more politically and culturally fragmented than once thought and not a unified and thoroughly Danish or Norwegian as suggested in The Anglo-Saxon Chronicles– but rather a mixture of various Scandinavian, Hiberno-Scandinavian and other so-called ‘second generation’ settlers.
Scotland, the Orkneys and the Shetlands
The Scandinavians had desires which extended beyond just Britain- northward into Scotland, and the Orkney and Shetland Islands. In Scotland, Scandinavian settlement appears to have been rather rapid, although unlike the Danelaw region the Vikings (Norwegians) who settled in Scotland appear to have done so in isolated pockets. One issue plaguing historians and archaeologists is a marked lack of historical writings in regards to the establishment and/or location Scandinavian settlements along the coasts of Scotland. In those areas where known Scandinavian settlements have been located, remains have been identified and genetic testing has determined that the Shetland Islands were settled by equal (~5-10%) numbers of males and females. Similar genetic testing of remains found in the Orkney Islands indicate that will approximately 30% of the islands inhabitants were descended from Scandinavian ancestors (44% in the Shetlands), again, as was the case in the nearby Shetlands the remains of Scandinavian settlers dated to the Late Eighth through Eleventh Centuries AD show approximately equal numbers of ethnically and genetically Scandinavian males and females. Genetic evidence of this kind indicates the strong likelihood that Scandinavian settlers of the northern coast and islands regions of Scotland were composed of family groups- possibly of an extended nature. In the words of Ceiridwen Edwards, “So, perhaps we had it wrong all these years and the vicious Viking warrior was really nothing more than a doting dad- but this does not seem to be the whole story.” While most historians likely aren’t ready to go this far… it does call for a renewed discussion on the topic.
While remotely located, and laying outside the sphere of the British Isles, the Scandinavian settlement of Iceland serves as an important an unique point of comparison. Largely dissimilar from the Danelaw region and completely reversed from the observations of Northern Scotland- the genetic studies of Iceland revealed results which followed what many would consider the time honored and notorious historical narrative of Viking expansion. In 2003, Geneticist Agnar Halgason and his team colleagues undertook and extensive genetic study of the relatively small population of Iceland. The results indicated that while nearly all Icelanders contained numerous chromosomal DNA markers with marked Scandinavian ancestry, nearly 87% of the populations’ mtDNA had distinct genetic markers associated with persons of Irish and Scottish (non-Scandinavian) ancestry. What this demonstrates is that while the original male colonists of Iceland were in fact Scandinavian, the majority of the females were either culturally Irish and/or Hiberno- Scandinavians transported to Iceland from Scotland or Ireland. “It seems in these areas [Iceland and Ireland], that Viking settlement was mainly for the unattached male, who subsequently ‘acquired’ partners from among the local populations [before settling in Iceland].”
In 2000, Historian N. Price put forward an iteration of the long held Scandinavian migration theory which added additional conditions and permutations on pre-existing models in his explanation of Viking settlement patterns in the region of Kiev and the Baltic region. This rather simple hypothesis offers that Scandinavian settlements were either proceeded by trade and/or raiding into areas on the established peripheries of Scandinavian control and influence. Then following the establishment of a successful settlement these ‘transplanted’ Scandinavians would themselves travel, trade and raid and possibly establish new settlements of their own. While it is possible that some Viking settlements were transitory- existing for only a few seasons before the inhabitants moved on, the existence of numerous large and structurally significant Viking settlements calls this assertion into question. The more likely scenario is that within one to three generations of being founded, these new settlements were themselves well enough established to in turn support the establishment of ‘newer’ settlements which became the ‘new’ frontier of Scandinavian exploration and settlement.
If correct in its assertion, the ‘leap-frog’ migration theory would constitute a renewed dialog and examination of many long held historical premises in regards to the Scandinavian invasion and settlement within the British Isles. One immediate implication is that while ‘waves’ of Scandinavian immigrants did in fact originate from regions traditionally associated with Scandinavian peoples (such as Denmark, Sweden and Norway), other important groups of secondary or second-generation Scandinavians played a significant role in the expansion of the Scandinavian sphere of influence during the Eighth through the Eleventh Centuries AD.
The impact of the Scandinavian migrations upon Europe during the Eighth through Eleventh Centuries can not be understated. Historian George Holmes makes the following insightful statement regarding this period of history, “the effects of the Viking experience were just as profound in Scandinavia itself as in the parts of northern Europe touched by the Viking raids.” Holmes goes on to add, “The [Viking] raids brought Scandinavia into much closer contact with the other parts of Europe, paving the way for conversion to Christianity, and bringing economic and social changes which were to lead to the political unification of Sweden, Norway and Denmark.” Beginning in the early Tenth Century and throughout the next century, the Scandinavians found themselves in the center of an ever increasing territory which shaped much of the history of northern Europe, particularly the British Isles.
As previously discussed, the Danelaw region was not homogeneous mixture of Danes and Norwegians. The presence of numerous Hiberno- Scandinavians at Chester show the settlement of second-generation Scandinavians who displayed a strong Scandinavian heritage, but one that had also been influenced by exposure and intermarriage with the indigenous Irish, had themselves settled in the Danelaw region. In addition, the presence of other second-generation Scandinavians within the Danelaw shows at least a tacit cultural acceptance of those born outside of the traditional Scandinavian homelands.
Further close examination of the Danelaw region itself presents some difficulties in the traditional historiography of England. While the Danelaw served as the nominal delineation between Scandinavian and English rule, it fails to show the overwhelming presence of Scandinavians in the British Isles or the relatively transitory nature of Scandinavians traveling into and out of the region. Despite the false narrative of historians such as Barrie Markham Rhodes who stated, “[The Scandinavians within the Danelaw established] farms and village communities [which] needed both men and women to run them, so the Vikings would have had to find themselves wives”– the genetic examination of archaeological evidence proves that relatively few Scandinavian males within the Danelaw took Anglo-Saxon women as wives, but instead relocated large numbers of Scandinavian women into the region. This evidence largely dispels any assertions that the Vikings arrived in Britain, killed all the men and subjugated their widows as wives, which implies a more peaceful co-existence between newly arrived Scandinavians and the native Anglo-Saxons. This should by no means imply that the two groups did not engage in protracted and often costly military campaigns against each other, but rather to imply the Scandinavian migration into the Danelaw resembled the military campaigns which were occurring in mainland Europe- with the caveat that the Vikings often arrived by boat. This new and less ruthless narrative of the Scandinavian settlements within the Danelaw region also offers possible new insights into the early agreements by Scandinavians and Anglo-Saxons to agree to peaceful negotiations and relative succession of hostilities, as well as the early acceptance of Christianity by Guthrum and by extension presumably that of many of his pagan subjects.
Conclusion and More Consideration
The Scandinavian migration of the British Isles is a complex narrative which is poorly served by encapsulation into short, dogmatic points of view. No single narrative can address what is observed in the Orkney Islands, Iceland or the Danelaw. In each case it is necessary to examine the available evidence and apply the latest scientific modes of inquiry to support or refine previously held positions and/or theories. What is evident is what begun as a forceful military expansion along the eastern shore of Britain was quickly followed by settlers who established themselves in the interior regions of the country. These settlers, while initially cultural isolationists (to various degrees), were not bent on the destruction or eradication of the native Anglo-Saxon population. The Danelaw region was not an area completely populated by Scandinavians and their thralls, but the acknowledgement of the preeminence of Scandinavian lordship over mixed population of Scandinavian settlers and the native Anglo-Saxons who continued to live, trade and worship largely as they had done before.
In a future article (date unknown), I will examine the Scandinavian migration and settlement patterns of Ireland, Normandy and the Baltic region in the hope of shedding even more light upon this fascinating subject. But with that, I must caution all of my students and readers that as powerful as DNA technology is… it does have theoretical and practical limitations. Quality archaeological and anthropological research will remain a fundamental component in the analysis and understanding of Medieval and Ancient History.
Sources & References:
Barrett, James H. “What Caused the Viking Age?” Antiquity 82, no. 317 (2008): 671-85.
Blair, John. The Anglo-Saxon Age: A Very Short Introduction. Oxford: Oxford University Press, 2000.
Fleming, Robin. Britain after Rome: The Fall and Rise, 400 to 1070. London: Penguin, 2011.
Graham-Campbell, James, and Robert A. Philpott. The Huxley Viking Hoard: Scandinavian Settlement in the North West. Liverpool: National Museums Liverpool, 2011.
Goodacre, S., and A. Helgason. “Genetic Evidence for a Family-based Scandinavian Settlement of Shetland and Orkney during the Viking Periods.” http://Www.nature.com/Heredity. January 2005. http://www.nature.com/hdy/journal/v95/n2/full/6800661a.html#bib14.
Helgason, A., G. Nicholson, K. Stefansson, and P. Donnelly. “A Reassessment of Genetic Diversity in Icelanders: Strong Evidence from Multiple Loci for Relative Homogeneity Caused by Genetic Drift.” Annals of Human Genetics Ann Human Genet 67, no. 4 (2003): 281-97. doi:10.1046/j.1469-1809.2003.00046.x.
Holmes, George. The Oxford History of Medieval Europe. Oxford: Oxford University Press, 1992.
Mcevoy, B., and C. J. Edwards. “Human Migration: Reappraising the Viking Image.” Heredity 95, no. 2 (2005): 111-12. doi:10.1038/sj.hdy.6800695.
McLeod, Shane. The Beginning of Scandinavian Settlement in England: The Viking ‘Great Army’ and Early Settlers, C. 865-900.
Ostrer, Harry and Karl Skorecki. “The Population Genetics of the Jewish People.” National Center for Biotechnology Information. Hum Genet. 2013 Feb; 132(2): 119–127. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3543766/
Richards, J. D. The Vikings: A Very Short Introduction. Oxford: Oxford University Press, 2005.
Schwartz, Marianne, and John Vissing. “Paternal Inheritance of Mitochondrial DNA.” New England Journal of Medicine N Engl J Med 347, no. 8 (2002): 576-80. doi:10.1056/nejmoa020350.
Sykes, Bryan, and Bryan Sykes. Saxons, Vikings, and Celts: The Genetic Roots of Britain and Ireland. New York: W.W. Norton &, 2006.
Sykes, Bryan. The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry. New York, NY: W.W. Norton, 2002.
“Genomic Sequences.” National Center for Biotechnology Information. http://www.ncbi.nlm.nih.gov/genome/.
“Anglo Saxon Chronicle.” Anglo Saxon Chronicle translated by James Ingram (1823). http://www.britannia.com/history/docs/asintro2.html.
 Sykes, Bryan. The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry. (New York, NY: W.W. Norton, 2002), 25
 “Genomic Sequences.” National Center for Biotechnology Information. Accessed December 09, 2015.
 Sykes, Bryan. The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry. (New York, NY: W.W. Norton, 2002), 29-31.
 Fleming, Robin. Britain after Rome: The Fall and Rise, 400 to 1070. (London: Penguin, 2011), 4-6, 40-41.
 Hadrian’s Wall is in fact south of Antonine’s Wall built during the mid Second Century AD. While ultimately unknown, Antonine’s wall likely served as a point of demarcation between pro-Roman Celtic tribes and hostile tribes living northward.
 Fleming, Robin. Britain after Rome: The Fall and Rise, 400 to 1070. (London: Penguin, 2011), 219-220.
 “Anglo Saxon Chronicle.” Anglo Saxon Chronicle translated by James Ingram (1823).
 Richards, J. D. The Vikings: A Very Short Introduction. (Oxford: Oxford University Press, 2005), 56-57 & 102-104.
 Sykes, Bryan. The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry. (New York, NY: W.W. Norton, 2002), 26-27.
 Ibid., 25.
 Schwartz, Marianne, and John Vissing. “Paternal Inheritance of Mitochondrial DNA.” New England Journal of Medicine (347, no. 8 2002), 576-80.
 Ostrer, Harry and Karl Skorecki. “The Population Genetics of the Jewish People.” National Center for Biotechnology Information. (2013), 123-125.
 Sykes, Bryan, and Bryan Sykes. Saxons, Vikings, and Celts: The Genetic Roots of Britain and Ireland. (New York: W.W. Norton &, 2006), 102-105.
 McLeod, Shane. The Beginning of Scandinavian Settlement in England: The Viking ‘Great Army’ and Early Settlers, (C. 865-900), 88-90.
 Sykes, Bryan, and Bryan Sykes. Saxons, Vikings, and Celts: The Genetic Roots of Britain and Ireland. (New York: W.W. Norton &, 2006), 260-262.
 McLeod, Shane. The Beginning of Scandinavian Settlement in England: The Viking ‘Great Army’ and Early Settlers, (C. 865-900),100-108.
 Ibid., 66-68.
 The burial site at Repton and Heath Wood consists of three separate burial areas, the first dating to the 9th Century. Unlike the burial mounds commonly associated with military action, these burials were accompanied by very few grave-goods with both sexes interred in similar states of adornment.
 McLeod, Shane. The Beginning of Scandinavian Settlement in England: The Viking ‘Great Army’ and Early Settlers, (C. 865-900), 109-110 &112-132.
 Graham-Campbell, James, and Robert A. Philpott. The Huxley Viking Hoard: Scandinavian Settlement in the North West. (Liverpool: National Museums Liverpool, 2011), 82-83.
 Ibid., 79.
 Ibid., 76.
 Ibid., 32.
 Blair, John. The Anglo-Saxon Age: A Very Short Introduction. (Oxford: Oxford University Press, 2000), 43.
 McLeod, Shane. The Beginning of Scandinavian Settlement in England: The Viking ‘Great Army’ and Early Settlers, (C. 865-900),201.
 Goodacre, S., and A. Helgason. “Genetic Evidence for a Family-based Scandinavian Settlement of Shetland and Orkney during the Viking Periods.” Www.nature.com/Heredity. January 2005.
 Mcevoy, B., and C. J. Edwards. “Human Migration: Reappraising the Viking Image.” Heredity 95, no. 2 (2005), 111-112.
 Helgason, A., G. Nicholson, K. Stefansson, and P. Donnelly. “A Reassessment of Genetic Diversity in Icelanders: Strong Evidence from Multiple Loci for Relative Homogeneity Caused by Genetic Drift.” Annals of Human Genetics Ann Human Genet 67, no. 4 (2003), et.al.
 Ibid., et.al.
 Mcevoy, B., and C. J. Edwards. “Human Migration: Reappraising the Viking Image.” Heredity 95, no. 2 (2005), 112.
 Barrett, James H. “What Caused the Viking Age?” Antiquity 82, no. 317 (2008), 676.
 Holmes, George. The Oxford History of Medieval Europe. (Oxford: Oxford University Press, 1992), 107-108.
 Ibid., 108.