text: These patterns are consistent with northward expansion of ancestry, 
  potentially starting before the Viking Age, into the Jutland peninsula 
  and Zealand island towards southern Sweden. The geographical ori- 
  gin of this ancestry is currently difficult to discern, as the available 
  samples from Iron Age central Europe remain sparse. The timing 
  of this expansion is constrained only by the samples available: this 
  ancestry is not observed in individuals from the Copenhagen area of 
  Denmark (around 100 ce–300 ce)6, an individual from the southern tip 
  of Sweden (around 500 ce)16, individuals from the Sandby Borg mas- 
  sacre site on Öland in present-day Sweden (around 500 ce)7 and 31 indi- 
  viduals from the mid-eighth century Salme ship burials in present-day 
  Estonia (Extended Data Fig. 9), who probably originated in central 
  Sweden6. Therefore, this ancestry transformation most likely post- 
  dated these individuals in each particular region and mostly occurred 
  in the second half of the first millennium ce. 
  
  To assess the full extent of the impact of this ancestry influx into 
  Scandinavia, we next aimed to understand the ancestry of individu- 
  als in Scandinavia during the Viking Age. Previous studies have sug- 
  gested that there was a diversity of ancestries in Scandinavia during this 
  period6,7,65, due to increased maritime mobility, but have not reported 
  per-individual ancestry estimates based on preceding ancestry. We 
  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). 