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It was already known that Q1a-L54 was found among ancient Hunnic and Alanic genomes (L330 branch), but also in modern Scandinavia and in places settled by the Vikings (L804 branch). The Scandinavian branch was estimated to have split from the main Amerindian branch (M3) 15 kya by Yfull and 17 kya by this paper. I did not have much information on the Z780 branch, which split before that. It turns out that it was also Amerindian, including Clovis/Anzick. In other words, the Scandinavian L804 branch emerged from the same founding population as those who would become the Native Americans. It's just that this branch went back west from Bering and crossed all Siberia until Scandinavia. That explains why some Northern Europeans have traces of Beringian and Amerindian-like autosomal DNA (e.g. in Harappa World K=16).