Gene Expression

The genetics of Fenno-Scandinavia

Population substructure in Finland and Sweden revealed by the use of spatial coordinates and a small number of unlinked autosomal SNPs:

We genotyped 34 unlinked autosomal single nucleotide polymorphisms (SNPs), originally designed for zygosity testing, from 2044 samples from Sweden and 657 samples from Finland, and 30 short tandem repeats (STRs) from 465 Finnish samples. We saw significant population structure within Finland but not between the countries or within Sweden, and isolation by distance within Finland and between the countries. In Sweden, we found a deficit of heterozygotes that we could explain by simulation studies to be due to both a small non-random genotyping error and hidden substructure caused by immigration. Geneland, a model-based Bayesian clustering algorithm, clustered the individuals into groups that corresponded to Sweden and Eastern and Western Finland when spatial coordinates were used, whereas in the absence of spatial information, only one cluster was inferred.

I’ve cut edited two of the most interesting figures below.

i-4ee9f135abd03e6d3f1430e7e3cdd163-swedefinnmap.jpg

Now a figure which illustrates genetic variation clustered by the counties. I’ve cropped and rotated the chart, but if you click it you will see it in its original non-inverted form.
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Here’s an interesting tidbit:

The principal component analysis clearly separated the Finnish regions and Eastern and Western counties from the Swedish as well as the Finnish regions and counties from each other…Geneland showed three clusters (Figure 3B), roughly corresponding to Sweden, Eastern Finland and Western Finland. Thus, Geneland was able to correctly identify the country of origin of the individuals despite the lower quality of the Swedish data. Interestingly, the county-level PCA…and Geneland…placed the Finnish subpopulation of Swedish-speaking Ostrobothnia closest to Sweden. This minority population originates from the 13th century, when Swedish settlers inhabited areas of coastal Finland…Our result is in congruence with earlier studies where intermediate allele frequencies between Finns and Swedes have been observed in the Swedish speaking Finns….

Are Swedish speaking citizens of Finland the descendants of Finnish speakers who acculturated to a Swedish identity? Or are they the descendants of immigrants from Sweden? These are the questions genetics allows one to explore.

Related: Genetic map of Europe; genes vary as a function of distance and The Genetic Map of Europe.

Comments

  1. #1 Lassi Hippeläinen
    September 15, 2008

    I thought that genetics has already answered years ago: they are Finns, who have adopted Swedish as their home language. During the Middle Ages there were good business reasons to do so. The map doesn’t show data about the Swedish-speaking southern coast, but there the situation should be the same as in Ostrobothnia.

    The only exception is Aland, where Swedish genes are fairly common, obviously due to the proximity to Sweden and its several capitals over the years (Sigtuna, Upsala, and Stockholm).

    The split to Eastern and Western tribes is well known in Finland. Usually it is attributed to the Lake Päijänne, which is a bit too large to cross with the kind of rowing boats that are used on other lakes.

  2. #2 jaakkeli
    September 15, 2008

    “I thought that genetics has already answered years ago: they are Finns, who have adopted Swedish as their home language.”

    Ha. This is the only safe, “PC” line in Finland, what people default to when they don’t want to worry about politics. A Finn interpreting genetics as not finding Finland-Swedes to be of entirely Finnish origins *will* be interpreted by some as an attack against a minority. A Swede stating so will of course be suspected of Germanic racialism. So, we’re stuck producing all these studies finding an obvious pattern without anyone ever pointing out the obvious.

    Notice that the exact places where the coastal populations aren’t so Swedish-speaking (SAT and NO) are the ones that aren’t so close to Sweden. Even more peculiarily, note that the southwestern coast’s Swedish population has always had a bit of a gap at Satakunta, which is exactly where the distance to Sweden is greatest on the coast. It’s between SSO and SWF which are both closer to Sweden!

    This is far from the first study to find this pattern (in some others it’s even more obvious) without pointing out how well it fits, much less studying it further by separating ethnicity (the coarse resolution ends up only sampling a mix of Finns and Finland-Swedes even in the heavily Swedish areas) and sampling the southern coast. And then we of course point out the “well-known” “split” to eastern and western tribes…

    “The split to Eastern and Western tribes is well known in Finland.”

    …never mind that most North Ostrobothnians are of western origin and dialect, so we aren’t even seeing that “split” here, and never mind that the study once again finds a “split” between western and eastern Finns *while having a full gap in sampling between western and eastern Finns!*

    Sheesh! If you took out a band of samples to separate Swedes in two and then found out that there’s a gap, would that be “evidence” of “population substructure”?

    (Are they using the same dataset to produce all these studies since they *always* seem to have the same sample gap?)

  3. #3 Marcus
    September 15, 2008

    Swedish-speaking Finns, or Finns of Swedish background are slightly over-represented in Finnish elites.

    Within Sweden, much of the commercialization was done by foreigners from the continent, with the Dutch and English building up southern and western towns, and other foreign minorities focusing on specific towns (for instance, Jews in Marstrand). Even the Swedish royal family were a French import.

  4. #4 razib
    September 15, 2008

    which is a bit too large to cross with the kind of rowing boats that are used on other lakes.

    haha. you’re too shy to row across big lakes!

  5. #5 Lassi Hippeläinen
    September 15, 2008

    @jaakkeli:

    1) The reason for NO being grouped with east is livelihood. The eastern folks were still heavily involved in hunting-gathering, and NO was their regular hunting ground. SW Finns were mostly agriculturalists. Their life style wasn’t feasible in the north. They only traded there (and with the Swedes).

    2) SAT and HAM are closely connected for a geographical reason: the most important traffic route from the coast to central Finland was the river valley of Kokemäenjoki.

    3) I’d be happy to see the results from those white areas that separate East from West. It’s not like they aren’t inhabited. The capital area alone contains a million people (20% of total population!) and is white on the map…

    @Razib: of course there was some traffic across Päijänne, but only when conditions were right. The boats were optimized for the 10’000 or so smaller lakes, uncounted rivers and creeks, and hauling across the ground between waters. Things like marriage were local things; so is language – the map of Finnish dialects looks much the same as that genetic map.

  6. #6 windy
    September 15, 2008

    Sheesh! If you took out a band of samples to separate Swedes in two and then found out that there’s a gap, would that be “evidence” of “population substructure”?

    It would, it just wouldn’t tell us what kind of substructure (clinal or not).

    Was anyone else surprised by the position of Skåne and Halland in the PCA?

  7. #7 magetoo
    September 15, 2008

    Being from “DAL”, I find it interesting that we’re apparently in one of the corners, and that our neighbours GAV, in another. Is this significant in any way? (Other than being inbred bastards the lot of us.)

    I wouldn’t be surprised to see some effects from migration and immigration here (due to the copper mine), but since I have no idea what the axes mean I’m not sure what to make of it.

  8. #8 jaakkeli
    September 15, 2008

    “The reason for NO being grouped with east is livelihood.”

    No, we’re talking *genetics*. By dialect and by known historical origin, NO is a *western* population, with only the easternmost bit being eastern (the county boundaries don’t always make perfect cultural sense). That’s my point: yeah, there is the deep difference between eastern and western Finnish, but dialect puts most of NO solidly on the western side, so whatever “population substructure” they’re supposedly finding here DOES NOT correspond to the eastern/western Finnish division we all know!

    I’ve yet to see the study that finds an actual “split” between eastern and western Finns. But I’m seeing plenty of hints that there is *one* relatively stark genetic boundary in Finland: inland/coast, brought on by the Swedes. Here we’re seeing a pattern of enhanced closeness to Sweden roughly following the level of Swedish population in the counties. More resolution and sampling by ethnicity is likely to make it look starker.

    “SAT and HAM are closely connected for a geographical reason: the most important traffic route from the coast to central Finland was the river valley of Kokemäenjoki.”

    I know. I’m from around there. Satakunta, by the way, is one of the really artificial constructs, so sampling it as a whole sucks. It makes no cultural sense whatsoever (it’s very old but it has never made that kind of sense, it’s always been just administrative) and there’s a very stark difference between the coast (which used to have some Swedish population) and the inland.

  9. #9 windy
    September 15, 2008

    By dialect and by known historical origin, NO is a *western* population

    I thought the Savonians colonized all the way to the coast so it should be a mixed population?

    I’ve yet to see the study that finds an actual “split” between eastern and western Finns.

    I think that most studies so far have been geared to find whether the Finnish population came from different “sources”. You don’t need to sample everywhere to show that your population is not perfectly admixed, but you are right that it’s premature to conclude genetic “gaps”.

    But one of the authors is a von Döbeln, so I suppose looking for gaps comes naturally… (sorry, bad Finnish in-joke)

    Here is a Y chromosome study with a geographically more complete sampling. As you suspected, the groups are more evenly spread out, but the substructure is still there.

  10. #10 windy
    September 15, 2008

    Being from “DAL”, I find it interesting that we’re apparently in one of the corners, and that our neighbours GAV, in another. Is this significant in any way? (Other than being inbred bastards the lot of us.)

    The differences between Swedish counties weren’t statistically significant in this study, but it’s certainly interesting that it’s so far off center. Better sampling could sort out whether there’s some real signal there.

    Maybe some weird old genetic types surviving in Älvdal, along with the language?

  11. #11 Richard
    April 9, 2009

    Did anyone actually ever bothered to read the study?

    This is the direct citat from the original version.

    “Clear East-West duality was observed when when the Finnish individuals were clustering using Geneland.[b]Individuals from the Swedish-speaking part of Ostrobotnia clustered with Sweden when a joint analysis was performed on Swedish and Finnish autosomal genotypes”[/b].

    Ulf Hannelius, 2008. Population genetic association and Zygosity testing on preamplified Dna. 2008

    The study sampled 20 Ostrobotnian Swedes on the west coast of Finland without checking the background of the donours. Despite the increase in the bi-ethnic intermarriages, the Finland-Swedish sample still formed a cluster with Mainland Swedes.

    This is actually a topic (the genetic of Finland-Swedes) which is the most taboo-laden issue in Finnish society. The Swedes in Finland enjoy a higher social prestige as opposed to Finns, and the “Swedishness” of Finland-Swedes is uncomfortable issue in Finland.

    History of Finland is Swedish. Reading Finnish history one never encounters name such as “Virtanen” (referring a common Finnish last-name) in Finnish history. It´s all Swedish. Denoting the Swedes in Finland as some sort of language shifters has been very popular among Finns, after all it´s only gimmick Finns have to make them appeared to have been inside the “club”. It´s just reflection of the low Finnish national self-esteem.

    Obviously the Swedes in Finland (and Sweden) have assimilated all kind of “foreign” ethnicities. Uralic-speaking Finns are just one ethnicity among the many.

  12. #12 Christian
    October 29, 2009

    Doesn’t anyone here realise that there are differences within the Finland-Swedes themselves? The swedish-speakers of Ostrobothnia are obviously connected to Sweden (probably the ones living on the coast south from Turku towards Helsinki as well), but those who live in the area around and in Helsinki aren’t necessarily so. That is the “elite” that so many are referring to. Many of them have very mixed backgrounds; German, Russian, Baltic, Finnish and so on. Even some Swedish :-). The thing that binds them together with other Finland-Swedes is language and similar experiences from the past 100 years.

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