Population genomics of the Viking world

[NNadir]

The paper I'll discuss in this post is this one: Population genomics of the Viking world (Eske Willerslev et al., Nature volume 585, pages390–396(2020))

According to "23 and me" analysis of my sister's-in-law genome, my wife is 30% (or maybe 32.38712% - I forget) French, which is news to me. I always kind of thought she was an American, and I have spent a lot of time in France among French people, I don't think my wife is French at all, or knows about how to be French, or wants to know about how to be French.

It gets a little silly in my view. These genetic ancestry companies, by the way, don't make any money by telling you about your remote relation to Anne Bolelyn's cousin's wife's brother's grandfather's adopted sister's great uncle's wife's bastard son. They make money by selling genetic distribution data to pharmaceutical companies, so they can figure out which diseases and syndromes are likely to be most profitable to manage and/or (god forbid) cure.

Nevertheless, there probably is some value in population genetics, and one area of active research is in physical anthropology, which can, if interpreted properly, surprise us by showing the commonality of our humanity, along with the beauty of diversity.

I came across this paper yesterday in desultory wandering around the literature, and it caught my eye because...because...well, honestly, I have no idea why it caught my eye but it seems to have done so. Following the references therein helped me make fun of one of my former intellectual conceits - which has now been considered to be vaguely (or maybe even grossly) racist - with respect to the disappearance of the Greenland Norse.

The main author listed in the reference next to the link - the authorship is quite a crowd - Eske Willerslev, is a pioneer in population genetics based anthropology, and according to his web page, is a world famous scientist and adventurer. Until yesterday, I never heard of him, but I'm a somewhat limited human being. For example, I know next to nothing about the Kardashian family except that one of them is apparently married to a famous African American Trumper, although I have no idea why the Trumper in question is famous.

Anyway, the abstract is available at the link above. From the introduction:

The events of the Viking Age altered the political, cultural and demographic map of Europe in ways that are evident to this day. Scandinavian diasporas established trade and settlements that stretched from the American continent to the Asian steppe1. They exported ideas, technologies, language, beliefs and practices to these lands, developed new socio-political structures and assimilated cultural influences2.

To explore the genomic history of the Viking Age, we shotgun-sequenced DNA extracted from 442 human remains from archaeological sites dating from the Bronze Age (about 2400 BC) to the Early Modern period (about AD 1600) (Fig. 1, Extended Data Fig. 1). The data from these ancient individuals were analysed together with published data from 3,855 present-day individuals across two reference panels (Supplementary Note 6), and data from 1,118 ancient individuals (Supplementary Table 3).

Here is a picture of some of the participants in this study, none of whom apparently gave "informed consent" to participate in the study, although there seems to have been no complaints from these subjects or their families about their uninformed lack of consent, which is probably a little less of ethical concern than say, the case of Henrietta Lacks, because the case of Henrietta Lacks involves some very questionable historical sociological implications:



The caption:

Extended Data Fig. 1 Viking Age archaeological sites.
Examples of a few archaeological Viking Age sites and samples used in this study. a, Salme II ship burial site of the Early Viking Age, excavated in present-day Estonia: schematic of skeletons (top left) and aerial images of skeletons (top right, and bottom). b, Ridgeway Hill mass grave dated to the tenth or eleventh century AD, located on the crest of Ridgeway Hill near Weymouth, on the south coast of England (reproduced with permission from Dorset County Council/Oxford Archaeology). Around 50 predominantly young adult male individuals were excavated. c, The site of Balladoole, around AD 900, a Viking was buried in an oak ship at Balladoole (Arbory) in the south east of the Isle of Man. d, Viking Age archaeological site in Varnhem, in Skara municipality (Sweden). Schematic map of the church foundation (left) and the excavated graves (red markings) at the early Christian cemetery in Varnhem; foundations of the Viking Age stone church in Varnhem (middle) and the remains of a 182-cm-long male individual (no. 17) buried in a lime stone coffin close to the church foundations (right).

By the way, the supplementary files, which are probably open sourced, have fascinating details about all the dead people participating in the study. The files are 178 pages long, if you have some time to kill, and are found here: Supplementary information


The text continues:

Although Viking Age Scandinavian populations shared a common cultural background, there was no common word for Scandinavian identity at this time1. Rather than there being a single ‘Viking world’, a series of interlinked Viking worlds emerged from rapidly growing maritime exploration, trade, war and settlement, following the adoption of deep-sea navigation among coastal populations of Scandinavia and the area around the Baltic Sea3,4. Thus, it is unclear to what extent the Viking phenomenon refers to people with a recently shared genetic background or how far population changes accompanied the transition from the Iron Age (500 BC–AD 700) to the Viking Age in Scandinavia.

The Viking Age Scandinavian individuals of our study fall broadly within the diversity of ancient European individuals from the Bronze Age and later (Fig. 2, Extended Data Figs. 2, 3, Supplementary Note 8), but with subtle differences among the groups that indicate complex fine-scale structure. For example, many Viking Age individuals from the island of Gotland cluster with Bronze Age individuals from the Baltic region, which indicates mobility across the Baltic Sea (Fig. 2, Extended Data Fig. 3). Using f4-statistics to contrast genetic affinities with steppe pastoralists and Neolithic farmers, we find that Viking Age individuals from Norway are distributed in a manner similar to that of earlier Iron Age individuals, whereas many Viking Age individuals from Sweden and Denmark show a greater affinity to Neolithic farmers from Anatolia (Extended Data Fig. 4a). Using the qpAdm program, we find that the majority of groups can be modelled as three-way mixtures of hunter-gatherer, farmer and steppe-related ancestry. The three-way model was rejected for some groups from Sweden, Norway and the Baltic region, which could be fit using four-way models that additionally included either Caucasus hunter-gatherer or East-Asian-related ancestry (Extended Data Figs. 4b, c)—the latter of which is consistent with previously documented gene flow from Siberia5,6,7.

Anatolia is the peninsula now wholly contained by the nation of Turkey, which is currently ruled by a Trump type, apparently. Irrespective of that fact, it's somewhat surprising to find that some Vikings were Turks.

The Viking World according to the authors, Fig. 1: Overview of the Viking Age genomic dataset:



The caption:

a, Map of the Viking World from eighth to eleventh centuries AD, showing geographical location and broad age category of sites with ancient samples newly reported in this study. Age categories of sites (circles) are coloured-coded as: dark green, LNBA (2400–500 BC); light green, Iron Age (500 BC–AD 700); yellow, Early Viking Age (AD 700–800); Viking Age (AD 800–1100); Medieval and Early Modern (AD 1100–1600). Red region, area of Viking origins; green region, area of Viking raids, settlement and trade; dark blue region, area of pioneer Viking colonization. b, All of the ancient individuals from this study (n = 442), and previously published Viking Age samples from Sigtuna10 and Iceland18, categorized on the basis of their spatiotemporal origin. The ancient samples are divided into the following five broad categories: Bronze Age (BA), Iron Age (IA), Early Viking Age (EVA), Viking Age (VA), Medieval (MED) and Early Modern (EM). Random jitter has been added along the x axis in each category to aid visualization. LNBA, Late Neolithic and Bronze Age; Norse W, Norse western settlement; Norse E, Norse eastern settlement; Norway S, southern Norway; Norway N, northern Norway; Norway M, middle Norway.

The next graphic apparently involves mapping from one real coordinate space to another (2 dimensional) coordinate space as a means of to determine "similarity" graphically. In one case, it's called "MDS" which is an abbreviation for multi-dimensional scaling and another, it's a "UMAP." I was frankly unfamiliar with these terms, which involve some nice mathematics involved in the area of statistics. Most of the statistics I know comes from taking courses in analytical chemistry, and some from osmosis over the years; but I've never actually taken a formal course in statistics, and certainly not in statistical similarity determinations in genomics. Poking around the internet showed me that apparently a UMAP is better than a tSNE, but I'm going in only so far as to say I've sort of, more or less, well, "in a fashion" have been there...

Anyway, similarity mappings, Fig. 2: Genetic structure of Viking Age samples:



The caption:

a, Multidimensional scaling (MDS) of n = 1,305 ancient genomes, on the basis of a pairwise identity-by-state sharing matrix of the Viking Age and other ancient samples (Supplementary Table 3). Outlier individuals with hunter-gatherer (VK531) or Saami-related ancestry (VK518 and VK519) are highlighted. b, UMAP analysis of the same dataset as in a, with fine-scale ancestry groups highlighted. HG, hunter-gatherer.

The authors continue:

To elucidate the fine-scale population structure of Viking Age Scandinavia, we performed genotype imputation on a subset of 298 individuals with sufficient (>0.5×) coverage (289 from this study, along with 9 previously published individuals10) and inferred the genomic segments they shared via identity-by-descent with a reference panel of present-day European individuals (n = 1,464) (Supplementary Notes 6, 10, 11). Genetic clustering using multidimensional scaling and uniform manifold approximation and projection (UMAP) shows that Viking Age Scandinavian individuals cluster into three groups by geographical origin, with close affinities to their respective present-day counterparts (Fig. 3a, Supplementary Fig. 10.1). Some individuals—particularly those from the island of Gotland in eastern Sweden—have strong affinities with Eastern Europeans; this probably reflects individuals with Baltic ancestry, as clustering with Bronze Age individuals from the Baltic region is evident in the identity-by-state UMAP analysis (Fig. 2b) and through f4-statistics (Supplementary Fig. 9.1).

The living and the dead, Fig. 3: Genetic structure and diversity of ancient samples.:




The caption:

a, UMAP analysis of n = 1,624 ancient and modern Scandinavian individuals, on the basis of the first 10 dimensions of MDS using identity-by-descent segments of imputed individuals. Large symbols indicate median coordinates for each group. b, Genetic diversity in major populations of the Scandinavian Viking Age. Plots next to the map show MDS analysis on the basis of a pairwise identity-by-state sharing matrix. Norway denotes all the sites from Norway. The scale is identical for all the plots.

And finally - trust me, Anne Boleyn is in here somewhere - Fig. 4: Spatiotemporal patterns of Viking and non-Viking ancestry in Europe during the Iron Age, Early Viking Age and Viking Age:





The caption:

We performed inverse distance-weighting interpolation of the ancestry painting proportions of each individual genome on a dense grid of points covering the European continent, to better visualize the distribution of ancestry paintings at different periods (Supplementary Note 12). Top, distinct spheres of influence in the Viking world. Middle, Danish Viking ancestry in southern Britain, Norwegian Viking ancestry in Ireland and Isle of Man and non-Scandinavian (‘North Atlantic’) ancestry in Orkney, Ireland and southern Britain. Bottom, Late southern European ancestry in southern Scandinavia. The Swedish-like ancestry is the highest in present-day Estonia owing to the ancient samples from the Salme ship burial, which originated from the Mälaren valley of Sweden (according to archaeological sources). n = 289 genomes used for interpolation.

Well then...

The authors discuss the disappearance of the Norse settlements in Greenland, an area of the world that is now famously melting at some threat to all of humanity, at least coastal humanity:

Disappearance from Greenland

From around AD 980 to 1440, southwest Greenland was settled by people of Scandinavian ancestry (probably from Iceland)28,29. The fate of these populations in Greenland remains debated, but probable causes of their disappearance are social or economic processes in Europe (for example, political relations within Scandinavia and changed trading systems) and natural processes, including climatic change29,30,31.

According to our data, the Greenland Norse populations were an admixture between Scandinavians (mostly from Norway) and individuals from the British Isles, similar to the first settlers of Iceland18. We see no evidence of long-term inbreeding in the genomes of Greenlandic Norse individuals, although we have only one high-coverage genome from the later period of occupation of the island (Supplementary Note 10, Supplementary Figs. 10.2, 10.3). This result could favour a relatively brief depopulation scenario, consistent with previous demographic models32 and archaeological findings. We also find no evidence of ancestry from other populations (Palaeo-Eskimo, Inuit or Native American) in the Greenlandic Norse genomes (Supplementary Fig. 9.4)

I always like to wonder through the references in interesting papers, and as such, I found my way to Reference 30, which is this one:

Cultural adaptation, compounding vulnerabilities and conjunctures in Norse Greenland (Dugmore et al., PNAS March 6, 2012 109 (10) 3658-3663)

At the end of the last century, and the beginning of this one, it was intellectually fashionable to embrace the ideas of Jared Diamond, who won the Pulitzer Prize for his book "Guns, Germs and Steel" which was followed by "Collapse: How Societies Choose to Fail or Succeed. I waxed romantic about the latter book, which I read, in a post over at DailyKos - where I was happily banned for reporting a scientific truth, albeit in a very crude way - in order to support the obsessive viewpoint, which is either amusing or dire, of which anyone familiar with my writings will be aware. A large section of the book is about the disappearance of the Greenland Norse, which Diamond attributes to a refusal to eat Salmon because of superstition.

The more recent criticism of Diamond is that his work is overwhelmingly Eurocentric, and quite possibly, racist, at least in a vague, or perhaps obvious, way.

Reference 30 in the paper under discussion in turn contains reference 34, which is to Diamond's "Collapse" about which Dugmore and his coauthors say the following:

Despite this early, large-scale use of marine fish in Iceland, the rarity of marine fish bones in any phase of Norse occupation—even recently excavated archaeofauna that have been carefully sieved for small bones—indicates that early settlers in Greenland decisively switched from cod to seal (32, 33). Although some explanations for this change invoke special pleading (34), it can be argued to be a pragmatic and effective adaptation driven by seasonal scheduling issues; the ice-riding harp and hooded seals arrived in the springtime, filling a potential late winter provisioning gap before the summer trips north for walrus hunting. Winter fisheries that did not compete with other subsistence were possible in Iceland but were less feasible in Greenlandic waters because of the formation of sea ice (35).

I love that locution referring to a logical fallacy, "special pleading," by which the authors dismiss Diamond's contention in "Collapse."

It has a certain trenchant eloquence, don't you think?

If there is any silver lining on the cloud of the near destruction of the United States by agency of having an ignorant racist lead it, it is that old white guys like me have had to reflect on their thinking and their assumptions, to question their immunity from being more than a little racist themselves, irrespective of their previous habits of thinking about themselves. This, I think, is a good thing. One is not really alive without questioning oneself.

The paper that is the general topic of this post concludes like this:

Our genomic analyses shed light on long-standing questions raised by historical sources and archaeological evidence from the Viking Age. We largely confirm the long-argued movements of Vikings outside Scandinavia: Vikings from present-day Denmark, Norway, and Sweden going to Britain, the islands of the North Atlantic, and sailing east towards the Baltic region and beyond, respectively. However, we also see ancient Swedish-like and Finnish-like ancestry in the westernmost fringes of Europe, and Danish-like ancestry in the east, defying modern historical groupings. It is likely that many such individuals were from communities with mixed ancestries, thrown together by complex trading, raiding and settling networks that crossed cultures and the continent...

... Some Viking Age Scandinavian locations are relatively homogeneous—particularly mid-Norway, Jutland and the Atlantic settlements. This contrasts with the strong genetic variation of populous coastal and southern trading communities such as in the islands of Gotland and Öland47,48,49. The high genetic heterogeneity in coastal communities implies increased population size...

...Finally, our findings show that Vikings were not simply a direct continuation of Scandinavian Iron Age groups. Instead, we observe gene flow from the south and east into Scandinavia, starting in the Iron Age and continuing throughout the duration of the Viking Age, from an increasing number of sources. Many Viking Age individuals—both within and outside Scandinavia—have high levels of non-Scandinavian ancestry, which suggests ongoing gene flow across Europe.

Perhaps, just perhaps, the "Scandinavians" are more human than Scandinavian.

I trust you are having a pleasant, safe, and healthy Sunday afternoon.

[Warpy]

1. In my readint years ago, I came across the bitter complaint of an Irish priest

that the local girls were running away with the Viking men because they were cleaner. I suppose men who smelt of the sea were preferable to the local lads who stank of peat smoke and sheep shit.

However, what needs to be remembered is that Vikings were traders, foremost. Oh, they pillaged monasteries full of gold and bling and captured slaves from undefended towns, but if they came upon a village full of peasants who could give them a fight, they'd pull out their purses and start to bargain.

All my European ancestry was qualified by "sort of" before they ever left for America because so few of them were farmers and tied to the land, most traveled. A cousin did do the ancestry test and found out the theoretically Alsatian side of the family was mostly Irish. I was not shocked. Ireland has always exported its people and mine were never farmers.

[abqtommy]

2. Thanks so much for this op that gives a lot of information using a somewhat humorous-aside

style I find very pleasing. Not to mention the colorful graphs that I enjoyed, so I won't mention them.
It all goes to show what I've long thought, that humans are well-traveled and very frisky in a randy
way so that in these days we're all related and truly part of the same family!

[NNadir]

5. I'm very happy to hear you appreciated the humor. The paper...

...certainly called up the inner sarcasm that runs through my brain when people sit around as some party or dinner discussing the results of their genetic tests and the alleged connection with Druid kings in 7th century Wales.

What is the point?

Of course, I may be a little jaundiced about these things, genetic reductionist theories. My father claimed to be of 1/4 Austrian decent, and frankly, late in life my father had a disturbing and uncanny facial resemblance to the pictures Adolf Eichmann as Eichmann looked in the protective glass box when he was on trial in Israel.

Then too, my mother-in-law used to tell me that the reason my sons did so well academically was that they had her genes, which came from "good" English and "good" German stock. All the time my wife and I put into the education of those boys had nothing to do with their success apparently.

I loved my mother-in-law in the end, but she certainly knew how to get on my nerves.

I was certainly in a mood for absurdity when reading and writing about this serious and fine paper and found that I couldn't help myself from coloring my post with some irony.

Genes may be useful for tracing migrations, and exploring disease syndromes, but they are decidedly not what defines human worth, character or the experience of humanity.

Thank you for your kind words.

[abqtommy]

6. You're welcome. It was my pleassure to read your words.

[eppur_se_muova]

3. This study included samples from as late as 1600, so that might show the influence of Norman Sicily.

Last edited Mon Sep 21, 2020, 10:20 AM - Edit history (1)

The Normans mingled with Arab-speaking Muslims ("Moors" ) and Greek-speaking Byzantines -- no doubt including some from Asia Minor, the heart of Byzantium -- in the parts of Sicily, lower Italy, and the northern coast of Africa which they controlled. And mercenaries on all sides were free of foot, and, well, mercenary in their allegiances.

https://en.wikipedia.org/wiki/Norman-Arab-Byzantine_culture#Norman_conquest_of_Africa

I was under the impression that a Sicilian coin, with Arabic script, had been found in a New England NA archaeological site a number of years ago (in fact, I ate lunch with the guy who found it -- IIRC) and was attributed to trade with Vikings. Unfortunately, the only references I can find to a Viking coin in the US are to the "Maine Penny", which was found much earlier. Perhaps I misremembered our conversation, or at least some of its details, and he only studied the find (and it wasn't minted in Sicily); the "Maine Penny", or "Goddard coin", has been studied repeatedly by a host of experts.

[NNadir]

8. Well that's an interesting story about the "Goddard Coin."

I downloaded a few papers about it.

Apparently the "Spillings Hoard" discovered buried under outhouse boards on the Swedish Island of Gotland, contains a considerable amount of silver that is clearly Islamic in origin.

I stumbled on that hoard while clicking around links connected to Gotland, one of the areas whose genetic history is discussed in the paper.

[Igel]

4. Lots of possible reasons for the connection with Anatolia.

Remember, "Turks" showed up in the 1200s/1300s, and largely just added their genetic stock to the area.

But the agrarian wave out of Anatolia probably led to increased population, which would have led to more people on the move.

Then again, Indo-Europeans had moved into Anatolia and also into Europe, so the connection may be a kind of confound--people moved from Central Asia into both places, but the data set just picks up the occurrence of those alleles in N. Europe and SE Europe.


This kind of thing is neat for bringing information to homeland and historical linguistic studies. Sort of "if the IE people were here, how, exactly, did they get there?" Useful to link the genetic data with linguistic data.

[NNadir]

7. I would guess - without offering any evidence - that your third paragraph is the most likely...

...explanation.

How well this genetic data interfaces with linguistic clues is beyond my ken, but the paper refers to the close relation between the inhabitants of Gotland - an Island off the coast of Sweden where Swedish is spoken and Baltic inhabitants. Some of the genetic material sample was from anthropological digs in Estonia.

Estonian, Finnish, and Hungarian, as you probably know, are Finno-Ugric languages of a class still represented in the Urals and trans-Ural regions, as is Sami.

To my knowledge, these languages are not related to Turkish; they are not even considered, I believe, to be Indo-European languages. Of course, this may be a result of historical political effects. The Dine language still exists, but I expect that it will ultimately disappear in Arizona and the language of the Dine people will be English, quite divorced from their genetic heritage.

The other Scandinavian languages, Danish, Norwegian, Swedish, Icelandic, and Faroese are all considered Germanic. I worked briefly for a Norwegian country, and although I never really got into their language, Norwegian had a decidedly Germanic sound, and one could hear here and there, German cognates, along with English cognates that litter all the world's languages these days.