Iron Age and Anglo-Saxon genomes from East England reveal British migration history

[Graham]

Iron Age and Anglo-Saxon genomes from East England reveal British migration history

Abstract

British population history has been shaped by a series of immigrations and internal movements, including the early Anglo-Saxon migrations following the breakdown of the Roman administration after 410CE.

It remains an open question how these events affected the genetic composition of the current British population. Here, we present whole-genome sequences generated from ten ancient individuals found in archaeological excavations close to Cambridge in the East of England, ranging from 2,300 until 1,200 years before present (Iron Age to Anglo-Saxon period). We use present-day genetic data to characterize the relationship of these ancient individuals to contemporary British and other European populations.

By analyzing the distribution of shared rare variants across ancient and modern individuals, we find that today’s British are more similar to the Iron Age individuals than to most of the Anglo-Saxon individuals, and estimate that the contemporary East English population derives 30% of its ancestry from Anglo-Saxon migrations, with a lower fraction in Wales and Scotland.

We gain further insight with a new method, rarecoal, which fits a demographic model to the distribution of shared rare variants across a large number of samples, enabling fine scale analysis of subtle genetic differences and yielding explicit estimates of population sizes and split times.

Using rarecoal we find that the ancestors of the Anglo-Saxon samples are closest to modern Danish and Dutch populations, while the Iron Age samples share ancestors with multiple Northern European populations including Britain.

http://biorxiv.org/content/early/2015/07/17/022723

[Graham]

The middle Anglo-Saxon samples from Hinxton (HS1, HS2, HS3) share relatively more rare variants with modern Dutch than the Iron Age samples

In East England, Wales and Scotland. Overall, these samples are closer to the Iron Age samples than to the Anglo-Saxon era samples.

There is a small but significant difference between the three modern British sample groups, with East English samples sharing slightly more alleles with the Dutch, and Scottish samples looking more like the Iron Age samples.

To quantify the ancestry fractions, we fit the modern British samples with a mixture model of ancient components, by placing all the samples on a linear axis of relative Dutch allele sharing that integrates data from allele counts one to five.

By this measure the East England samples are consistent with 30% Anglo-Saxon ancestry on average, with a spread from 20% to 40%, and the Welsh and Scottish samples are consistent with 20% Anglo-Saxon ancestry on average, again with a large spread.


In summary, this analysis suggests that only 20-30% of the ancestry of modern Britons was contributed by Anglo-Saxon immigrants, with the higher number in East England closer to the immigrant source.

The difference between the three modern groups is surprisingly small compared to the large differences seen in the ancient samples, although we note that the UK10K sample locations may not fully reflect historical geographical population structure because of recent population mixing.

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We next applied rarecoal to 524 samples from six populations in Europe to estimate a European demographic tree into which we could place the ancient samples.


There was a marked difference between the Iron Age and the Anglo-Saxon era samples: the Anglo-Saxon era samples mostly merged onto the Dutch and Danish branches, whereas the Iron Age samples preferentially merged at the base of the ancestral branch for all modern Northern European samples .


The exception is that the early Anglo-Saxon O4 shows the same signal as the Iron Age samples, consistent with the rare allele sharing analysis.

There is some differentiation amongst the Anglo-Saxon era samples, with early AngloSaxon samples having highest likelihood of merging onto the Dutch branch while O3 and the middle Anglo-Saxons have highest likelihoods of merging onto the Danish branch.

Interestingly, when we placed modern samples onto the tree using the same method, samples from most countries placed on the tip of their respective branch, but GBR samples, collected from Kent, Cornwall and Orkney as part of the Peoples of the British Isles collection placed at varied positions, with some at the top of the northern European subtree near the Iron Age samples.

[Catkin]

Great paper, thanks for posting. The analysis by rare allele sharing is really interesting.

[Hevo]

Thanks Graham, The Dutch are the tr00 Anglo-Saxons.:P

[Graham]

Thanks Graham, The Dutch are the tr00 Anglo-Saxons.:P
Yeah the early Anglo-Saxons & going by the English language similarity with the Frisian Language. It adds up.
http://s22.postimg.org/nhf2zgm41/angles.jpg

[Neon Knight]

the East England samples are consistent with 30% Anglo-Saxon ancestry on average ... and the Welsh and Scottish samples are consistent with 20% Anglo-Saxon ancestry on average

Not a big difference between English and Scottish/Welsh then, whereas the PotBI results showed a Saxon+Danish element of about 3% in the North Welsh, 6% in the South Welsh and 2-13% in the Scots. However, the 30% estimate of AngloSaxon ancestry for the English is consistent with the average PotBI estimate of 25%.

http://i657.photobucket.com/albums/uu295/Alchemyst/PotBI%202015%20Britain%20Map%20My%20Version_zpswv5 8tnlo.jpg

So, either the Welsh and Scottish samples in this latest study are heavily mixed with English (at least half English in fact) or the AngloSaxons eventually did go to Wales and Scotland in significant numbers but without changing the languages. What do you think?

[Golf]

Interesting stuff, thanks for the share and for the abridged version.

Bunch of immigrants after all :vikingship:

[Gooding]

What an interesting article! Thanks so much for posting this, it gives one some insight into the genetics of the populace of Great Britain, England especially.

[de Burgh II]

Makes sense, probably explains where R1b-U106 comes from...

[Kamal900]

I guess that the English and their Celtic neighbors can finally see each other as close brethren then.

[Graham]

So, either the Welsh and Scottish samples in this latest study are heavily mixed with English (at least half English in fact) or the AngloSaxons eventually did go to Wales and Scotland in significant numbers but without changing the languages. What do you think?

Scots 20% will mostly be Norse. 30% AS in East English will literally be Anglo Saxon.

[Hevo]

Yeah the early Anglo-Saxons & going by the English language similarity with the Frisian Language. It adds up.
http://s22.postimg.org/nhf2zgm41/angles.jpg

The ''new'' Frisians in Coastal Netherlands were basically Anglo-Saxons but some Jutes, remaining Frisii and other minor North Sea Germanic groups migrated to the Coastal Netherlands aswell.

[Neon Knight]

Scots 20% will mostly be Norse. 30% AS in East English will literally be Anglo Saxon.

If they've not been able to distinguish between Norwegian and Danish/Saxon DNA then their study is not much use as a measure of AngloSaxon genetic impact. Did they use PotBI data for their Welsh and Scottish samples? I find it hard to believe they would not have made sure their pop. samples were properly representative. But if they are good samples then, like I said, the relatively high AS % in the Welsh, at least, needs explaining.

[Graham]

There is no ancient Norse data currently to compare with the Anglo Saxon data & they didn't use PotBi.

There is an Iron Age Swede kicking about though. That could have been used but didnt.

[Neon Knight]

We should also remember that these ancient DNA samples from a few individuals are not-never-no way statistically significant and this can be seen as no more than a pilot study. PotBI remains the best one so far, easily.

[Brianna]

If they've not been able to distinguish between Norwegian and Danish/Saxon DNA then their study is not much use as a measure of AngloSaxon genetic impact. Did they use PotBI data for their Welsh and Scottish samples? I find it hard to believe they would not have made sure their pop. samples were properly representative. But if they are good samples then, like I said, the relatively high AS % in the Welsh, at least, needs explaining.

That's a good point. How could they separate Germanic tribes from later Danish invaders from Norwegian Vikings from some Normans? The labels almost seem like arbitrary guesswork. FE, there were Germanic settlers in southern Scotland. One could use historical geography as a guide, but, as the article states, there's been a lot of population changes over the many years. I buy the basic premise of the study. I'm not sure about the specific divisions. FE, Danes arrived at different times. They also were genetically close to other Germanic arrivals. We can separate the Iron Age group from the "Anglo-Saxon" group. Can we correctly and definitively separate the latter group from other genetically close groups? Can we divide the "Anglo-Saxon" group into smaller groups? It seems like we would need a gargantuan amount of samples to do so. I doubt that even that would be foolproof. I sometimes think it's better to refer to just one northern European continental group when we're unsure of the specific subgroups within it.

[Neon Knight]

There's a discussion on it in this forum: http://www.anthrogenica.com/showthread.php?4943-Iron-Age-and-Anglo-Saxon-genomes-from-East-England-reveal-British-migration-history

I might join just to put my points across.

[Graham]

We should also remember that these ancient DNA samples from a few individuals are not-never-no way statistically significant and this can be seen as no more than a pilot study. PotBI remains the best one so far, easily.

Potbi will be one step behind until it uses ancient samples rather than modern. But from they have said in the past, this will happen & the results will be great when we get them.

Regarding the faults in this study, is the numbers. There's not enough people to get a proper result of Scotland, England & Wales.

[Neon Knight]

Potbi will be one step behind until it uses ancient samples rather than modern. But from they have said in the past, this will happen & the results will be great when we get them.

Regarding the faults in this study, is the numbers. There's not enough people to get a proper result of Scotland, England & Wales.

It appears they did not apply the 4 granndparents rule and used people who were simply born in England, Scotland and Wales. Very sloppy.