f3- and f4-statistics

Shared genetic drift between two populations (or individuals) since their divergence from an ancestral population was computed using the outgroup f₃-statistics. The qp3pop program of ADMIXTOOLS (57) package was used with the “inbreed: YES” option on the Human Origins dataset described above to calculate f₃-statistics for the tree-like topology in the form of f₃(Outgroup, Test Population, Modern Population) in which the Yoruba population was used as Outgroup, each of the 40 ancient Siberians was used as Test Population, and 194 modern populations from the Human Origins dataset were used as Modern Population. Significant deviations from zero indicated a deviation from the proposed tree-like topology; thus, more positive values indicated an excess of shared genetic drift between the Test Population and Modern Population. The f₄-statistics for the tree-like topology of the shape f₄(Outgroup, Test; Group1, Group2) measures the shared genetic drift between Test Population and Group1 and Group2. Assuming no recent interactions between each of these four groups, tree topologies are balanced at zero, and deviation from zero implies a deviation from this proposed tree. Positive values indicate that Test population shares more alleles with Group1, and negative values indicate that Test population shares more alleles with Group2. Using the qpDstat program of ADMIXTOOLS (57) package with the “f4mode:YES” option, f₄-statistics were calculated for a set of tree-like topologies.