A genetic perspective on the recent demographic history of Ireland and Britain

[Capitalis]

Thank you for the clarification. That seems to answer the question!

I looked up your Y-DNA SNP at FTDNA Discover and noticed that you share Y-DNA ancestors with the two Medieval Ballyhanna, Co. Donegal samples. So I've requested that they be converted to G25, although I don't know their coverage.

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If anyone can tell me which paper this sample is from I'd be thankful, as I can't work it out by looking at Lara Cassidy's list of papers; she wasn't lead author of a 2018 paper.

Lagore 14 was a man who lived between 1492 - 1665 CE during the Historical Age and was found in the region now known as Lagore, Meath, Ireland.

Reference: LG14 from Cassidy 2018

Silly me, it's her PhD, which is now unembargoed again: A Genomic Compendium of an Island: Documenting Continuity and Change across Irish Human Prehistory (tcd.ie)

[Capitalis]

I think something went awry when the authors computed the effective population size for Cornwall at generation 100.



The confidence interval for Cornwall_2 gives a range of 150,000 to 13,500,000,000 (!). That's 13.5 billion.

[Capitalis]

We chose to split ROH and IBD segments into the corresponding bins (a) 1 to 3cM [1,3cM), (b) 3 to 5cM [3,5cM), and © greater than or equal to 5cM (≥5cM). Using the methodology above, these length bins correspond to 100 generations ago, 40 generations ago and 15 generations ago respectively. An important caveat is that the estimates have very wide distributions, as well as the aforementioned assumption of population size.

If we take a generation as 28 years, then we have:

[1,3cM) ≈ 100 generations ago ≈ 776 BCE
[3,5cM) ≈ 40 generations ago ≈ 904 CE
(≥5cM) ≈ 15 generations ago ≈ 1604 CE

As an alternative to the PCA plots of IBD sharing in Supplemental Figure 13 which include all of the Isles, I've created PCA plots isolating the IBD sharing at ≥5 cM for,

The Isles (excluding Orkney and Isle of Man) and Europe


Compare this plot with the plot of IBD sharing for [3,5cM) ≈ 40 generations ago ≈ 904 CE.



As noted previously, the 3-5 cM IBD sharing plot is reminiscent of the modern Isles structure found in a G25-based PCA plot.

My interpretation is that the modern Isles population was essentially "set" at the 3-5 cM IBD sharing stage, as the plot of ≥5 cM IBD sharing doesn't recover the expected structure within the Isles. If you have a different take, do reply.

The Isles and France


The Isles and Belgium


The Isles and Germany / Poland


The Isles and Denmark / Sweden


The Isles and Norway


The Isles and Finland


The Isles and Italy / Spain


All data is from Supplementary Table 8.

[Capitalis]

If it’s not too much trouble, could you add me to your plots with the other members?

Interested in the Leinster info as that is where my 1812 patrilineal brick wall was born (Wicklow)

I only included Medieval / Viking Ireland samples with coverage of at least 0.1x.



The "Atlantic drift" has been present in Ireland, or Co. Roscommon at a minimum, since 700-1300 CE. So although most modern Irish "forum member" samples plot to the right, those who plot to the left have been with us for a good while.

Imagine sitting on samples for going on six years, by the way...

[Mitchell-Atkins]

Thanks for including me. I’m closest to Northumberland, followed by Cumbria/Tyne & Wear tied for 2nd, then Durham next closest.

I typically get a ~60/40 split between Anglo Saxon vs IA Briton, so being slightly closer to Anglian Northumberland than Briton Cumbria would make sense. Plus it’s on the Scottish border and Scotland is my closest modern population.

Edit: Plus I came out closest to this Celt_Brythonic_North/Brythonic_Brigantes IA pop in this thread so that lines up.

https://genarchivist.com/showthread.php?...1#pid12631

[Capitalis]

Thanks for including me.  I’m closest to Northumberland, followed by Cumbria/Tyne & Wear tied for 2nd, then Durham next closest.

I typically get a ~60/40 split between Anglo Saxon vs IA Briton, so being slightly closer to Anglian Northumberland than Briton Cumbria would make sense.  Plus it’s on the Scottish border and Scotland is my closest modern population.

I don't know your regional Isles ancestry, except that your largest ancestral group is English, but I'm often thinking about Garimund's PCA plot position, as it should be somewhere much further north than it is given his ancestral populations, and so I wonder if the following may apply to other North Americans, depending on how long ago their ancestors emigrated.

sktibo once disagreed with me that LivingDNA was accurate, and we could say the same about a G25 PCA plot for Garimund, and I think there may be the following issue. I'll use a mixed Isles example.

If a modern person's ancestors, we'll call him Jim, left the West Country in 1650 CE, Wales in 1700 CE and Ulster in 1750 CE, and emigrated to a small settlement in North America, then they would only have carried with them a percentage of the genetic variation that existed in each of those source populations.

For the next 300 years in the West Country, the population would have mixed fairly freely and shared in the wider genetic variation. But in the subset of the West Country population in our North American settlement, they could potentially experience some combination of a founder effect or a bottleneck, either of which could cause the North American West Country folk to drift from their English West Country relatives.

If this also occurred in our North American settlement's Welsh population and Ulster population, then we now have multiple layers of drift in effect, which seems theoretically plausible as people sometimes take a number of generations to marry outside their origins; e.g. my grandmother was 100% Irish even though her ancestors had been in South Wales for a long time.

Jim might plot in exactly the right position on a G25 PCA plot compared to his close North American relatives, who also share in the drift of this North American settlement. But a combination of his more distant West Country / Welsh / Ulster relatives "back home" in the Isles won't produce the expected G25 coordinates because they haven't undergone the same drift.

So I look English / Irish / Welsh in the expected amount at LivingDNA because I'm not drifted enough from the PoBI / Irish samples they're comparing me with, but perhaps sktibo has undergone a change in allele frequency due to North American drift, and so now looks more [fill in the blank] than expected. Maybe Danish / French / German.

I don't know how long ago my North American Anthrogenica acquaintances' ancestors left the Isles, so this concept may not apply to everyone. Feel free to take offense. :-)

If this topic, specific to North America, has been covered by a professional research paper, please post a link if you, the reader, know of one.

[Mitchell-Atkins]

My focus is more a curiosity of what my genetic makeup is most similar to rather than any actual ancestral homeland as I’ve got British and Irish ancestors from dozens of locations.

3-6 generations back in Montgomeryshire, Wales
5 generations, Montrose, Scotland, Folkestone, Kent
6 generations, Wicklow, Ireland, West Grimstead, Wiltshire.
7 generations, Antrim, Ireland, Ross and Cromartie, Scotland

But the vast majority of my lines are still in the US before 7 generations.


Not sure if anyone else played with it but I used that “ Evil twin” tool at gedmatch a few years ago

http://jenniferhsrn.blogspot.com/2016/11...n.html?m=1

Basically someone who inherited the exact opposite of what you got from both parents.

My “evil twin” is much more Celtic, much less Germanic than me. Same parents but relatively distant location on a Brit/Ir-ish plot

Based on the county labels on your plot, my “genetic hometown” might be Berwick upon Tweed.

[Nqp15hhu]

LivingDNA isn’t accurate to be honest. My father scores ~40% SW Scotland and NI, I supposedly score ~2%!

[JonikW]

My LivingDNA results were good when I tested at their launch and became useless with the update a few years ago. Sktibo had a contact there and kindly raised my case but to no avail. He's not here under a different name is he? I used to enjoy his contributions at AG.

[Webb]

My LivingDNA results were good when I tested at their launch and became useless with the update a few years ago. Sktibo had a contact there and kindly raised my case but to no avail. He's not here under a different name is he? I used to enjoy his contributions at AG.

The last time I saw him post was mid to late Covid Pandemic, going off memory.

[Capitalis]

i’m pretty sure Cassidy found that a minority of irish late Iron Age (which is roughly parallel with Roman period in Britain) pulled away from typical (pure bronze age Irish) towards western Britain.

It's unclear which of my posts you were replying to as you didn't use the quote function, but I assume you were responding to, 



"Note also the persistent migration barrier between Wales and Ireland."

One last time...

Lara M. Cassidy, A Genomic Compendium of an Island Documenting Continuity and Change across Irish Human Prehistory (2017)

Quoted from pp. 168-171, Table 4.1 List of samples from the Late Neolithic to Early Modern periods analysed in the current chapter



I count 25 Iron Age samples and 2 (Early) Modern samples from Ireland. I can identify these samples on the PCA plots that follow.

Quoted from p. 185,

Several of the major principal components (PCs) identified explain little of the variation present in the ancient dataset. This includes the first and third PCs (Fig. 4.6A), which respectively segregate the populations of Orkney and Wales, while compressing the remainder of modern and ancient variation. The presence of strong haplotypic differentiation between these populations and the rest of Britain was reported in the original publication of the dataset [...].

[...]

The driving factor behind haplotypic divergence of Welsh populations is less clear. However, we note here that, alongside modern individuals from the border regions of Wales, the entire Irish Early Bronze Age population (several southwestern samples excluded) is also pulled away from the main cluster and in the direction of Welsh individuals on PC3 (Fig. 4.6A), suggesting they possess some haplotypic variation found in Wales that is absent in the remainder of the dataset. Surprisingly, the same increased affinity is not seen for the Iron Age Britons of Yorkshire and southeastern England, as may have been expected given both the persistence of Brittonic Language and culture in Wales after the Anglo-Saxon migrations, and the previously demonstrated affinity of the Yorkshire individuals to the modern Welsh population (Martiniano et al. 2016). This could indicate that the prolonged regional isolation of Wales, aided by its mountainous geography, stretches into the Bronze Age period, allowing the build up of the extensive haplotypic diversity seen in PC3.

To reiterate, the Irish EBA samples "possess some haplotypic variation found in Wales that is absent in the remainder of the dataset". That absence would include the Ireland Iron Age samples.

Quoted from p. 186, Figure 4.6A. PCA of haplotypic similarity of ancient and modern individuals from Britain and Ireland



Focus on the left side image. Note that the non-Ireland ancient samples are shades of red and grey. The Ireland Iron Age samples are downwards triangles. They are visibly "north" of the Ireland Bronze Age samples, moving away from South and North Wales, rather than towards it. Nothing in this PCA plot contradicts the quoted passage above.

Quoted from pp. 185-187,

The second component of variation (Fig. 4.6B-C) is unique in that it explains a large amount of variation present in both ancient and modern individuals.

[...]

Irish Iron Age samples extend the entire range of Irish variation on PC2, suggesting substantial continuity with the modern population. Irish Early Bronze Age samples show a more constricted distribution closer to the center of the plot, but still exhibit a systemic shift towards Irish Iron Age and modern populations, particularly those from individualised burials. The most parsimonious explanation for such observations is direct continuity between the Chalcolithic/Early Bronze Age and modern period in Ireland, with much of the haplotypic variation explained by PC2 forming in the intervening millennia, in a similar manner as suggested for Wales in PC3. While migration may be partially responsible for this structure, it is worth noting that the Irish Iron Age and modern population typically extends away, rather than towards, any potential external sources of variation in the dataset, including a contemporary Iron Age population from Britain, the most likely source of migration into Ireland between the Bronze Age and Early Christian periods. However, several exceptional Irish Iron Age samples exist, returned to in later sections.

Quoted from p. 186, Figure 4.6B. PCA of haplotypic similarity of ancient and modern individuals from Britain and Ireland



Focus on the right side image. The Ireland Iron Age samples are downwards triangles. I'm struggling to identify the "exceptional" samples.

Quoted from pp. 188-189,

PC4 appears to capture much of the ancient haplotypic variation missing in PC2 (Fig. 4.6C), and exhibits a clear temporal trend. Modern variation is compressed around the zero mark, with Iron and Bronze Age individuals forming approximate layers along the component’s axis.

[...]

A millennium separates Inchagreenoge134 and the earliest Irish Iron Age burial (Knowth10), in which time considerable haplotypic variation is seen to have built up on the island.

[...]

Notably, the only other LBA individual considered (Cherrywood1), places within Irish Iron Age variation on both PCs 2 and 4 (Fig. 4.6C), necessitating a more cautious interpretation of the indirectly dated burial (1,400-1,000 cal BC), which is not considered further in results or discussion.

[...]

The Iron Age population also shows some correlation between PCs 2 and 4, showing a diagonal distribution between the British Iron Age population and modern individuals from the west of Ireland. Intriguingly, two contemporaneous individuals from the same burial site (Lehinch) form the extreme ends of this distribution, suggesting some level of mobility in the community to which they belonged. Lehinch28 and HillOfWard14 are in fact indistinguishable from British Iron Age variation, and may potentially represent recent arrivals from the neighbouring island.

Aside from Inchagreenoge134 (a Late Bronze Age sample from Co. Limerick), all of the other samples highlighted in the quote above are from Central Leinster. I have highlighted in red all samples from Late Bronze Age and Iron Age Central Leinster in the PCA plot below.

Quoted from p. 186, Figure 4.6C. PCA of haplotypic similarity of ancient and modern individuals from Britain and Ireland



The cline of Central Leinster Iron Age samples identified in the quote above is clear, with Central Leinster Late Bronze Age sample Cherrywood1 also on this cline but "not considered further in results or discussion".

This cline is on the road to nowhere, not to Iron Age Britain. In fact, the three Iron Age Cambridgeshire samples (deep red downwards triangles) can more correctly be described as having clearly shifted from Britain to Ireland. A Medieval England sample (deep red diamond) is also clearly heading towards the Iron Age Central Leinster cline.

This is also visible on PC 2 and PC 6.



So what we actually have here is evidence for population movement spanning the Iron Age to Medieval Age, from Ireland to England, probably from Central Leinster.

Cheers. :-)

[Cejo]

Thank you for the clarification. That seems to answer the question!

I looked up your Y-DNA SNP at FTDNA Discover and noticed that you share Y-DNA ancestors with the two Medieval Ballyhanna, Co. Donegal samples. So I've requested that they be converted to G25, although I don't know their coverage.

---

If anyone can tell me which paper this sample is from I'd be thankful, as I can't work it out by looking at Lara Cassidy's list of papers; she wasn't lead author of a 2018 paper.

Lagore 14 was a man who lived between 1492 - 1665 CE during the Historical Age and was found in the region now known as Lagore, Meath, Ireland.

Reference: LG14 from Cassidy 2018

Silly me, it's her PhD, which is now unembargoed again: A Genomic Compendium of an Island: Documenting Continuity and Change across Irish Human Prehistory (tcd.ie)

Thanks for pointing this out, and for requesting those G25 samples. I don't know how to use them, but thanks, regardless! 

I looked at my ancient connections on FTDNA a bit more (which I hadn't made much use of, so thanks also for pointing this out), and found some additional context. Ballyhanna 331 is my closest ancient match - we share R-A18276 (TMRCA ~300CE). FTDNA lists the y-haplogroup as R-FT77253, as a subclade under R-A260. I think this makes the sample most closely related to the Ui Briuin dynasties of Connacht (ie: O'Connor), which makes some sense for that area, since they expanded into Breifne (ie: O'Rourke).

   

Ballyhanna 197 is listed as R-DF105, which places it slightly more distantly related (TMRCA ~250 CE). DF105 includes several ancient matches, including multiple Medieval Gaelic samples in Kilteasheen, Roscommon, the Lagore 14 sample, as well as a one culturally Viking Ireland sample in Dublin (Ship Street Great 12), and a Faroe Islander (Faroe 17). None show additional subtypes, though I assume they aren't actually basal DF105 (especially Lagore 14, who lived much later).