Sikeliot
06-08-2018, 11:40 PM
http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1007152
Some of these are my own interpretations but anything quoted came directly from the study.
1. In Ireland, South Munster (Cork/Kerry) is the most distinct of the Irish genetic clusters, likely the most authentically ancient Irish, due to the geographic isolation of the region.
"South Munster (SMN) and Cork (CRK) clusters branch off first in the fineSTRUCTURE tree and show distinct separation from their neighbouring north Munster clusters (NMN), indicating that south Munster’s haplotypic makeup is more distinct from its neighbouring regions and the remaining regions than any other cluster. TVD analysis supports this observation (S1 Table and S3 Table), with the Cork cluster in particular showing strong differentiation from other clusters. This may reflect the persistent isolating effects of the mountain ranges surrounding the south Munster counties of Cork and Kerry, restricting gene flow with the rest of Ireland and preserving older structure."
2. Modern English are considerably closer to the Roman Era Britannic population than to the Anglo-Saxons, though the highest Anglo-Saxon contribution is, of course, in southeast England.
The Anglo-Saxons were almost entirely made up of the red component, while the Roman era (RM) cluster consists of individuals closely matching that of modern day England, with both the red and green component. The red component is, of course, lowest in western England (Cornwall, Devon, border regions with Wales, Cheshire) and northern England (Yorkshire, Cumbria, Northeast England), but we cannot say the red component in the English is entirely or even mostly Saxon, considering its prevalence in the Roman era sample. It was, though, lower in the Iron Age sample, implying, possibly, continued migration from the continent or even that some of the Celtic groups came from regions where it was present.
TL;DR: the green component is higher when Celtic ancestry is higher, but the red component is not necessarily Saxon, given its presence in Britannic samples from the Roman age.
https://i.imgur.com/ELb8k9b.png
3. Celtic populations in Britain likely had genetic variation among themselves, hence a Cornwall/Devon/South Wales cluster and a North Wales/North England cluster that both separate in opposite directions from the most heavily Saxon "SE England" cluster.
"As observed in Fig 1, ChromoPainter PCA in Ireland and Britain (Fig 2) demonstrates eastern homogeneity for each island and relative diversity on the west coast. The southeast England (SEE) cluster group is centred at zero on PC4, representing a group with predominantly Anglo-Saxon-like ancestry (S8 Fig). Clusters representing Celtic populations harbouring less Anglo-Saxon influence separate out above and below SEE on PC4. Notably, northern Irish clusters (NLU), Scottish (NISC, SSC and NSC), Cumbria (CUM) and North Wales (NWA) all separate out at a mutually similar level, representing northern Celtic populations. The southern Celtic populations Cornwall (COR), south Wales (SWA) and south Munster (SMN) also separate out on similar levels, indicating some shared haplotypic variation between geographically proximate Celtic populations across both Islands. It is notable that after the split of the ancestrally divergent Orkney, successive PCs describe diversity in British populations where “Anglo-saxonization” was repelled [22]. PC3 is dominated by Welsh variation, while PC4 in turn splits North and South Wales significantly, placing south Wales adjacent to Cornwall and north Wales at the other extreme with Cumbria, all enclaves where Brittonic languages persisted."
https://i.imgur.com/gcmZvlE.png
4. Southern Scotland is genetically close to Ireland, and ancestry related to northern England/southern Scotland is more prevalent in the north of Ireland than in the south which may be due not only to the Plantations but also due to migration from northern Ireland to Scotland, which brought the Gaelic language.
"Scotland is another region of Britain which successfully retained its Celtic language, however in contrast to Welsh and Cornish clusters, the majority of Scottish variation is described by ChromoPainter PC1. The three definable Scottish groups do not drive any further components of variation (up to PC7 considered) and fall away from the bulk of British variation on PC1 towards Irish clusters. This is most strikingly observed for the southern Scottish cluster (SSC) which fell amongst Irish branches in the fineSTRUCTURE tree, overlapping with samples from the north of Ireland in PC space (Fig 2 and Fig 5). In an interesting symmetry, many Northern Irish samples clustered strongly with southern Scottish and northern English samples, defining the Northern Irish/Cumbrian/Scottish (NICS) cluster group. More generally, by modelling Irish genomes as a linear mixture of haplotypes from British clusters, we found that Scottish and northern English samples donated more haplotypes to clusters in the north of Ireland than to the south, reflecting an overall correlation between Scottish/north English contribution and PC1 position in Fig 1 (Linear regression: p < 2×10−16, r2 = 0.24)."
5. Viking ancestry in Ireland is highest in the following regions:
"This was recapitulated to varying degrees in specific genetically- and geographically-defined groups within Ireland, with the strongest signals in south and central Leinster (the largest recorded Viking settlement in Ireland was Dubh linn in present-day Dublin), followed by Connacht and north Leinster/Ulster (S5 Fig; S6 Table). "
6. Both Britain and Ireland have a gradient where the east of the islands have absorbed more Germanic input than the West.
In England, Celtic ancestry gets higher as you go north and west, and in Ireland, the highest amount of Germanic input is in the east, with the exception of Viking ancestry in Connacht.
Some of these are my own interpretations but anything quoted came directly from the study.
1. In Ireland, South Munster (Cork/Kerry) is the most distinct of the Irish genetic clusters, likely the most authentically ancient Irish, due to the geographic isolation of the region.
"South Munster (SMN) and Cork (CRK) clusters branch off first in the fineSTRUCTURE tree and show distinct separation from their neighbouring north Munster clusters (NMN), indicating that south Munster’s haplotypic makeup is more distinct from its neighbouring regions and the remaining regions than any other cluster. TVD analysis supports this observation (S1 Table and S3 Table), with the Cork cluster in particular showing strong differentiation from other clusters. This may reflect the persistent isolating effects of the mountain ranges surrounding the south Munster counties of Cork and Kerry, restricting gene flow with the rest of Ireland and preserving older structure."
2. Modern English are considerably closer to the Roman Era Britannic population than to the Anglo-Saxons, though the highest Anglo-Saxon contribution is, of course, in southeast England.
The Anglo-Saxons were almost entirely made up of the red component, while the Roman era (RM) cluster consists of individuals closely matching that of modern day England, with both the red and green component. The red component is, of course, lowest in western England (Cornwall, Devon, border regions with Wales, Cheshire) and northern England (Yorkshire, Cumbria, Northeast England), but we cannot say the red component in the English is entirely or even mostly Saxon, considering its prevalence in the Roman era sample. It was, though, lower in the Iron Age sample, implying, possibly, continued migration from the continent or even that some of the Celtic groups came from regions where it was present.
TL;DR: the green component is higher when Celtic ancestry is higher, but the red component is not necessarily Saxon, given its presence in Britannic samples from the Roman age.
https://i.imgur.com/ELb8k9b.png
3. Celtic populations in Britain likely had genetic variation among themselves, hence a Cornwall/Devon/South Wales cluster and a North Wales/North England cluster that both separate in opposite directions from the most heavily Saxon "SE England" cluster.
"As observed in Fig 1, ChromoPainter PCA in Ireland and Britain (Fig 2) demonstrates eastern homogeneity for each island and relative diversity on the west coast. The southeast England (SEE) cluster group is centred at zero on PC4, representing a group with predominantly Anglo-Saxon-like ancestry (S8 Fig). Clusters representing Celtic populations harbouring less Anglo-Saxon influence separate out above and below SEE on PC4. Notably, northern Irish clusters (NLU), Scottish (NISC, SSC and NSC), Cumbria (CUM) and North Wales (NWA) all separate out at a mutually similar level, representing northern Celtic populations. The southern Celtic populations Cornwall (COR), south Wales (SWA) and south Munster (SMN) also separate out on similar levels, indicating some shared haplotypic variation between geographically proximate Celtic populations across both Islands. It is notable that after the split of the ancestrally divergent Orkney, successive PCs describe diversity in British populations where “Anglo-saxonization” was repelled [22]. PC3 is dominated by Welsh variation, while PC4 in turn splits North and South Wales significantly, placing south Wales adjacent to Cornwall and north Wales at the other extreme with Cumbria, all enclaves where Brittonic languages persisted."
https://i.imgur.com/gcmZvlE.png
4. Southern Scotland is genetically close to Ireland, and ancestry related to northern England/southern Scotland is more prevalent in the north of Ireland than in the south which may be due not only to the Plantations but also due to migration from northern Ireland to Scotland, which brought the Gaelic language.
"Scotland is another region of Britain which successfully retained its Celtic language, however in contrast to Welsh and Cornish clusters, the majority of Scottish variation is described by ChromoPainter PC1. The three definable Scottish groups do not drive any further components of variation (up to PC7 considered) and fall away from the bulk of British variation on PC1 towards Irish clusters. This is most strikingly observed for the southern Scottish cluster (SSC) which fell amongst Irish branches in the fineSTRUCTURE tree, overlapping with samples from the north of Ireland in PC space (Fig 2 and Fig 5). In an interesting symmetry, many Northern Irish samples clustered strongly with southern Scottish and northern English samples, defining the Northern Irish/Cumbrian/Scottish (NICS) cluster group. More generally, by modelling Irish genomes as a linear mixture of haplotypes from British clusters, we found that Scottish and northern English samples donated more haplotypes to clusters in the north of Ireland than to the south, reflecting an overall correlation between Scottish/north English contribution and PC1 position in Fig 1 (Linear regression: p < 2×10−16, r2 = 0.24)."
5. Viking ancestry in Ireland is highest in the following regions:
"This was recapitulated to varying degrees in specific genetically- and geographically-defined groups within Ireland, with the strongest signals in south and central Leinster (the largest recorded Viking settlement in Ireland was Dubh linn in present-day Dublin), followed by Connacht and north Leinster/Ulster (S5 Fig; S6 Table). "
6. Both Britain and Ireland have a gradient where the east of the islands have absorbed more Germanic input than the West.
In England, Celtic ancestry gets higher as you go north and west, and in Ireland, the highest amount of Germanic input is in the east, with the exception of Viking ancestry in Connacht.