text: Here, we propose an approach that we refer to as ‘time-stratified 
  ancestry analysis’ to boost the statistical power of*f*-statistics 
  several-fold by using inferred genome-wide genealogies (Fig. 1a) and 
  apply our method to reconstruct the genetic history of northern and 
  central Europe from around 500 bce to 1000 ce.  We implement this idea of studying the ‘twigs’ of gene trees in a tool, 
  Twigstats (Fig. 1a and Methods), which we demonstrate in simulations 
  
  Nature | Vol 637 | 2 January 2025 |**119**