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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%).Danes are paternally mostly descended from North Germanic speaking proto-Danes, and maternally from West Germanic Angles and Saxons. English are paternally mostly Anglo-Saxon + Danish Viking, and maternally British/Welsh.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).
Icelanders and Irish are similarly almost like half-brothers from another father.
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