The Hallstatt effect (?)

Just to see what would happen, I ran a subset of the highest coverage Bronze Age samples from what is now Britain and Ireland in my new Celtic vs Germanic Principal Component Analysis (PCA). Look for the Britain_&_Ireland_BA cluster. The relevant datasheet is available here.

Perhaps it’s not a coincidence that the likely Celtic-speaking Iron Age individuals from what is now England (labeled England_IA) are positioned between these older British and Irish samples and the two ancients from Iron Age burials in Bylany, Czechia, associated with the Hallstatt culture (marked with black stars). That’s because the Hallstatt people are generally considered to have been the earliest speakers of Celtic languages.
Hence, what the PCA might be showing is a genetic shift in the British and Irish Isles caused by the arrival of Hallstatt Celts in Northwestern Europe.
Interestingly, the present-day English samples appear to be a mixture of Britain_&_Ireland_BA, England_IA and England_Anglo-Saxon. However, a subset of these samples is also heavily shifted “east” towards one of the Hallstatt individuals and present-day Dutch, suggesting that they harbor extra admixture from continental Europe.
This isn’t easy to make out on my plot, because of the clutter, but I can assure you that it’s true. Keep in mind that you can plug the datasheet into the PAST program (freely available here) to have a much closer look at the PCA and even change the color coding.
To check whether England_IA can be modeled as a mixture of Britain_&_Ireland_BA and Hallstatt with formal methods, I ran an analysis with the qpAdm software using all of the publicly available Bronze Age samples from what are now Britain and Ireland. The standard errors are high, probably because Britain_&_Ireland_BA and Hallstatt are closely related, but, overall, we can probably say that the model does limp across the line.

England_IA
Britain_&_Ireland_BA 0.555±0.172
Hallstatt 0.445±0.172
chisq 18.513
tail prob 0.100973
Full output

However, the really important thing about this output is that England_IA cannot be modeled as simply Britain_&_Ireland_BA (the chisq and tail prob are way off). Thus, even though the Hallstatt samples from Bylany don’t appear to be ideal proxies for the admixture in England_IA that is lacking in Britain_&_Ireland_BA, the signal they produce does suggest that a closely related population arrived in the British Isles after the Bronze Age to give rise to England_IA.
See also…
Celtic vs Germanic Europe

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