text: **Viking Age mobility into Scandinavia**
  Previous studies had suggested a major influx of ancestry related to 
  Britain into Viking Age Scandinavia6,7. Although we detect this ances- 
  try in some individuals (7 individuals in Norway, 14 in Denmark and 
  14 in Sweden), including some individuals whose ancestry appears to 
  be entirely derived from Iron Age Britain, its overall impact appears 
  reduced compared with previous reports. Our analysis indicates a pro- 
  portionally larger impact of ancestry from Iron Age Britain in northern 
  Norway, with southern Scandinavia predominantly influenced by 
  continental central European ancestries (Fig. 4d). We hypothesize 
  that our estimates of ancestry from Britain are reduced relative to 
  previous studies because ancestry related to Britain and continen- 
  tal central Europe may have been indistinguishable. This could be 
  due to a lack of statistical power to distinguish these closely related 
  sources with standard methods, as well as through potential biases 
  introduced by using modern surrogate populations that have since 
  been influenced by later gene flow (such as gene flow into Britain). 
  We illustrate this by replicating the analyses previously described6,7 
  (Extended Data Fig. 8). 
  
  Similarly, a previous study has suggested that individuals at sites such 
  as Kärda in southern Sweden carried ancestry from southern Europe6. 
  In our models, two Kärda individuals fit with central European-related 
  ancestry, but none of the individuals has a substantial proportion of 
  ancestry related to southern European sources (Extended Data Fig. 9). 
  Instead, we detect ancestry from southern European sources in only 
  three individuals from Scandinavia, and in relatively small propor- 
  tions (Fig. 4a). 