Do Danes Have Brythonic Admixture?

[Figaro]

Was there truly a significant-enough contribution from British thralls to make an impact on the modern population?

[J. Ketch]

There is around 10% Insular Celtic like ancestry in Denmark. This could have come from Irish, Scottish, Welsh/Britons or English.

[Figaro]

There is around 10% Insular Celtic like ancestry in Denmark. This could have come from Irish, Scottish, Welsh/Britons or English.

I guess I assumed Brythonic/English because of England being the primary target of Danish vikings. Ten percent seems like the number of thralls sent to Scandinavia was significant and not rare.

[J. Ketch]

I guess I assumed Brythonic/English because of England being the primary target of Danish vikings. Ten percent seems like the number of thralls sent to Scandinavia was significant and not rare.
The bulk of that Insular Celtic ancestry in Denmark could well come from English for the reason you say, but the early English of the Danelaw were quite heavily Anglo-Saxon and less Briton, so if it does come from English thralls then the English ancestry in Danes would be quite massive, over double that.

There was an admixture study a few years back showing Danes had a larger ancestral affinity to the British than any other country, but it was assumed that it was because of the heavy Danish + related Anglo-Saxon ancestry in England rather than British ancestry in Denmark, which would be a turn-up for the books.
https://www.genetics.org/content/204/2/711

Figure 3B and Table S2 show that the Swedish, Norwegian, and British clusters made the most substantial contribution to the ancestry profiles of all six Danish groups, jointly accounting for 82.05–97.12% of the total admixture. The Scandinavian component (Swedish and Norwegian clusters together) surprisingly accounted for less than half of the total admixture (range: 41.69–48.96%), on a par with the British component (40.37–48.16%), which peaked in South Jutland. Interestingly, the contribution of the Swedish cluster alone (27.45–30.20%) was almost twice as large as that of the Norwegian cluster (14.24–18.76%). This difference could be explained by the reduced landscape connectivity between Norway and Denmark, affecting gene flow patterns. It is also striking that the German cluster had little genetic influence on Denmark (3.04–6.78%), despite the proximity and historically fluid borders between the two countries. However, the latter observation could be due to the marginally higher genetic affinity of Denmark with Britain, which could result in prioritizing British over German samples in the initial chromosome-painting step of our analysis. Similarly, the French component was present at small yet considerable portions (4.16–5.42%) in all Danish regions except for Funen and South Jutland. Finally, it is worth noting that there was a small Polish contribution to Zealand (6.28%) and Funen (5.03%).

In general, the study of admixture within the European continent is confounded by a well-grounded isolation-by-distance mechanism (Lao et al. 2008; Novembre et al. 2008), as well as an increased historical complexity that renders most admixture models unrealistically simple (Busby et al. 2015). Denmark is no exception to these caveats. Even though it is tempting to explain the admixture proportions in Figure 3 and Figure 4 as the result of historical admixing events, an alternative approach is to interpret such proportions as “mixture profiles.” Bearing this in mind, we see that the mixture profiles of all six Danish groups comprise two major ancestry components, one predominant in Scandinavia and the other predominant in Central Europe (Figure 4). In the GLOBETROTTER analysis, these two components were identified as admixture contributions from the Swedish/Norwegian and the British clusters (Figure 3B and Table S2). In regard to the British contribution, however, this is actually more likely to reflect admixture in the opposite direction, i.e., from Denmark to Britain (Leslie et al. 2015).
https://oup.silverchair-cdn.com/oup/backfile/Content_public/Journal/genetics/204/2/10.1534_genetics.116.189241/9/m_711fig3.jpeg?Expires=1736286679&Signature=chd32Wu15zIrn6G3KxI6Ib~IBmBcHYhJww3gOVRN qsOG5UTpMxSXmEEnUMZZ8yDXsMLxBepqben~~w5T-5n4kz~kuFjaghY4inNYCjKi8ZjBrIXod03U4ldHNOrfclHZsCj dlpEbXVtW-VOpG~1C6igAABGMxkDjXl1FGvpz343PH8OHKYmAHafBr8p2Ld9 Yh7uhVndIuo1i0yRPGmwlZZ80zNlqSFBKYzU3LAOjxyiJdmSaZ xqImYmK8DfQoXP5kYUylVsHosDNg1FpV8zWlQeysx0UWFjPWjT a2zaKgyWAeX-Ni1xFbTLk6634imDTVmvWmfeo0gC5yBMkAfuDJA__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA

[Russki]

23andMe customers from Denmark and Western Norway on average score within the 10-20% range of "British & Irish";
23andMe customers from Central Norway on average score within the 5-10% range of "British & Irish";
23andMe customers from Eastern Norway and Sweden on average score within the 1-5% range of "British & Irish".

The Danes have from 5% to 19% surplus of "British & Irish" over the Eastern Norwegians and Swedes, and even the Eastern Norwegians and Swedes themselves have some B & I from the Viking Age.

https://sun9-39.userapi.com/impg/ddvXb9cHl4LUgd3eJ4mX_DNjin7hc0koT1vWmg/xqWqThA2pSc.jpg?size=800x581&quality=95&sign=3b084193345500a2d7b2251c9680f083&type=album