text: We additionally perform non-parametric multidimensional scaling 
  (MDS) on outgroup-*f*3 statistics44 computed using Twigstats, the results 
  of which do not depend on any modelling assumptions and which show 
  increased resolution compared with conventional outgroup-*f*3 sta- 
  tistics (Fig. 2a,b, Extended Data Fig. 6 and Supplementary Table 2). 
  Encouragingly, the MDS model supports regional fine-scale genetic 
  structures reflected in our source groups, such as the separation of 
  predominantly Norwegian and northern Swedish EIA individuals from 
  southern Peninsular Scandinavia (Fig. 2a); this relationship is not 
  detected without Twigstats. In this MDS analysis, we note a close affinity 
  of wide-ranging individuals from Portugal, France, Germany, Austria 
  and Britain. We hypothesize that this corresponds to areas associated 
  with the Celtic-speaking world, and that their close genetic affinity is 
  due to earlier expansions. Sparse sampling limits our understanding 
  of the full extent of regional ancestry variation in central Europe and 
  some other regions, but the continental ancestries differentiated in 
  the MDS model suggests that major ancestry variation across Europe 
  in this period is relatively well captured. 