The final presentation at the International Vinland-Seminar in Chicago (October 16, 2010) was Stephen Harding’s “Searching for Viking DNA.” Harding is Professor of Applied Biochemistry at the University of Nottingham School of Biosciences and serves as co-director of the National Centre for Macromolecular Hydrodynamics. He is the author of Ingimunds Saga: Norwegian Wirral and Viking Mersey and a co-author of both Wirral and Its Viking Heritage and Viking DNA: The Wirral and West Lancashire Project. He also wrote “Norway’s ‘Colony’ of Wirral, Liverpool,” which was published in Torgrim Titlestad’s Viking Norway.
It was interesting to see how the seminar’s academic presenters reacted to Harding’s talk. Intimately acquainted with each other’s research and findings on the Vínland sagas, the Norse exploration of North America, and so forth, the presenters can be forgiven if they weren’t on the edges of their seats for the day’s papers. However, when Harding began to explain his study of Viking DNA in England, the scholars really did perk up and pay rapt attention. It was wonderful to see the appreciative response given to the lone scientist at a seminar centered on saga lore!
Throughout his talk, Harding sought to dispel misconceptions about what DNA can tell us regarding genealogy. For instance, he pointed out that there is no direct Viking ancestry in the region known as Vínland, since the original Norse explorers returned to Scandinavia without leaving descendents behind in the New World.
As part of the team behind the Viking DNA in Northern England Project, Harding has made trips to Norway to gather control data for research into English DNA. In the Viking Age, the east of England was a Danish settlement and the northwest coast was controlled by the Norwegians (who had come around and through Ireland and Scotland).
Changing slowly through time and varying between individuals, DNA provides “messages from our ancestors.” DNA from skeletons provides direct and “real” information from the past, but is laden with problems. It is difficult to gather, sometimes of poor quality, prone to contamination, and often (if the skeleton’s owner has no living descendants) a dead end.
A better working solution is to analyze the DNA of modern, living people. It is quite easy to gather samples, but these samples can actually turn out to be unrepresentative of past populations. In order to deal with this problem and draw meaningful conclusions, Harding’s team had to develop new methods of inference.
Earlier attempts to trace ancestry focused on the genetics of physical characteristics. Focus on blood groups was ineffective, as such typing was “poorly discriminating” and the various groups were too widespread. Pigmentation, stature, and facial shape were also dead ends for research, as these constructed categories were too complex, poorly understood and (like blood types) widely distributed in northern Europe. Although genetics of eye and hair color distribution are becoming better understood, the approach remains “rather unscientific.”
A strangely literary approach to the genetics of physical characteristics focused on the distribution of a condition known as Dupuytren’s Disease. Also known as digitopalmar contracture, the disease manifests in the inability to relax the fourth and fifth fingers, which remain bent and rolled into the palm. In the Longer Saga of Magnus of Orkney, a pilgrim named Sigurðr is mystically cured of an affliction that matches the symptoms of Dupuytren’s Disease. Contemporary British cases of digitopalmar contracture are more frequently found in Viking-influenced parts of Britain, and can help to trace Viking descent. However, the disease also appears in other, non-Viking-related populations, which makes definitive conclusions difficult.
The modern method of searching for genetic markers of inheritance focuses on studying DNA. The Y of the male XY pair is preserved unchanged through the male line, while mitochondrial DNA is passed down only by women. This means that any given man has two lines of ancestry that can be traced and an individual woman has only one (because of her XX pair). In other words, DNA allows us to follow only the maternal line of a female subject but both the maternal and paternal line of a male subject. Helpful to researchers is the fact that patrilineal surnames are linked to the Y chromosome down through the generations – outside of Iceland, at least, where last names change with each generation.
Haplogroups are, in a sense, branches of the human family tree that can be categorized by differences in DNA-variations. For example, Haplogroup A is the oldest and is found in Africa. Throughout human history, new groups and subgroups have developed through mutation. There are major haplogroup differences between the inhabitants of the various continents, and there are different distributions of sub-haplogroups within Europe. Haplotypes are groupings of DNA sequences that are inherited together. When attempting to determine the Viking ancestry of an individual, haplotype information can give a detailed picture.
A recurring theme of Harding’s presentation was the unreliability and vagueness of result provided by online and commercial entities claiming to analyze an individual’s DNA in order to provide ancestral information. To use the free online Y-STR Haplotype Reference Database (YHRD), a male subject enters his haplotype numbers (provided, for example, by a mouth-swab DNA test). YHRD then traces Y-chromosome ancestry and provides a report. Although the YHRD website claims that “chromosomal profiling can trace back paternal lineages into the past and has thus been proven a useful tool in genealogical and kinship testing,” Harding argues that the system provides very vague results. It gives the user some general idea of their ancestry, but it is not at all definitive.
To underscore the difficulty of determining any individual person’s specific ancestry, Harding provided a simple mathematical example. Any given individual has two biological parents (obviously). Each of those parents has two parents of their own, which means that the generation that is two steps back already has four ancestors (22 = 4). If we go back forty generations, the individual has 240 ancestors in that generation (240 = 1,099,511,627,776). This is, of course, a statistical construct, as forty generations back (approximately 1200 CE) the world had (according to scholarly consensus) only around 400,000,000 inhabitants. This all goes to show that (1) we’re all related if we go back far enough and (2) it’s simply not feasible to give a definitive ancestry for an individual.
The solution that Harding and his team have come up with is to focus on admixture approaches to “population Viking ancestry,” as more secure ancestry conclusions can be made at the population level (≥20 people) than at the individual level. The group studied the distribution of Y-chromosome types and looked at the admixture of parental and hybrid populations. Norse Viking and Celt are both defined as parental groups, while groups like the Norse-Gaels of Scotland are considered hybrids.
A 2005 paper by Goodacre, Helgason et al. analyzed mitochondrial DNA (mtDNA) and Y-chromosome markers to determine patterns of male and female ancestry in Scandinavian settlement of Shetland and Orkney during the Viking Age. Historically interesting is the fact that territories settled closer to the Scandinavian homelands show roughly equal traces of both male and female Viking ancestry – meaning that Norse settlers brought their families with them to new lands. Farther afield, the results show Viking male ancestry mixed with a greater proportion of British and Irish female ancestry – meaning that, in the farther settlements , Viking men arrived alone and mated with local or “imported” women. This “male-biased” Viking ancestry is most prominent in Iceland.
Harding’s own work on Viking DNA has focused on Northern England. There are a great many place names around Liverpool that show Norse origin. Most notable is the village of Thingwall, the name of which derives from Þingvellir, the legal assembly-field of Nordic society. Thingwall is known for a hill that is believed to be an ancient Þingbrekka – an assembly-hill from which the Lawspeaker’s legal announcements were made. Much archaeological evidence of Norse presence in the area has also been discovered.
Harding’s team ran into the problem of large population movements that followed the Industrial Revolution. Their solution was to test two different populations in Wirral and West Lancashire. The first group (“Modern”) was made up of men who could prove they had grandparents from the area. The second group (“Medieval”) consisted of men who had grandparents from the area and who also had a last name that could be proven to exist in the area before 1600 (through examination of Medieval tax records, court cases, church records, and so forth). The results showed that the Medieval group had a greater proportion of Norse ancestry (approximately fifty percent). When common last names were removed from the Medieval group, the Norse proportion rose to more than half.
Harding briefly outlined the second part of his team’s research (due later in 2011), which focuses on North Lancashire, Cumbria and North Yorkshire. It includes the “Gamle Norge” (“Old Norway”) project, which seeks to provide better controls for the English tests by gathering DNA samples from more remote areas of Norway.
In conclusion, Harding underlined the idea that individual genetic testing for ancestry might be interesting, but that one has to be careful making specific conclusions from the results, since testing gives no definitive answer. Results are much more powerful and meaningful on a population basis. His own group’s results are interesting on both social and historical levels, confirming that Northwest England’s coastal regions were areas of heavy Viking settlement.
No comments:
Post a Comment