text: **qpAdm modelling.**In brief, qpAdm models are a generalization of 
  *f*4-ratios, for which one-, two- and three-source models can be tested as 
  hypotheses and admixture components and their s.e. obtained with a 
  block jackknife13. A qpAadm model is fully specified by a set of putative 
  source groups and additional ‘outgroups’ that are used to distinguish 
  source ancestries. We used a rotating approach in which we itera- 
  tively selected a subset of source groups and used all remaining puta- 
  tive sources as outgroups. This approach penalizes models where true 
  contributing sources are used as outgroups. With sufficient statistical 
  power, qpAdm models will be statistically rejected if true contributing 
  sources are used as outgroups. If statistical power is more limited, 
  several models will fit the data, but the correct model is expected to 
  be preferred over wrong models. Throughout, we use the Relate gene- 
  alogies of SGDP modern and imputed ancient genomes in our qpAdm 
  modelling and first compute*f*2-statistics using the Twigstats function 
  f2_blocks_from_Relate between all populations involved, which we then 
  feed to the ADMIXTOOLS2 package70. 