analysed each individual’s ancestry using a rotational qpAdm scheme 
(Fig. 4a, Extended Data Fig. 9 and Supplementary Table 4), which 
showed increased power in distinguishing models when restricted 
to recent coalescences with Twigstats (more than 80% of accepted 
one-source models in Twigstats were also accepted one-source models 
using all SNPs, compared with less than 17% for the inverse).
We investigated regional differences in non-local ancestry across 
Scandinavia. In Denmark, 25 out of 53 Viking Age individuals had detect-
able (z-score > 1) central European-related ancestry (CentralEurope.
IronRoman or Portugal.IronRoman) in their best accepted qpAdm 
models. In Sweden 20 out of 62 individuals had detectable central 
European-related ancestry, concentrated almost entirely in southern 
regions (Fig. 4a,d). By contrast, in Norway, this ancestry was observed 
in only 2 out of 24 individuals, indicating a wide-ranging impact of 
incoming ancestry in southern Scandinavia and suggesting more