Simple demographic models and QTP. a–d) Topological structures of the four simple demographic models. e–h) QTP and number of plausible qpAdm models across the historical range ([0, 0.02]) of median pairwise F_ST values calculated on the S1, S2, R1, R2, and R3 populations and ≤100 generations since the admixture event forming the target population. For each simulation iteration, we represent the counts of the number of plausible single- and two-source qpAdm models (21 is the maximum possible) with orange dots and the locally estimated scatterplot smoothing (loess) computed in R and shown with the orange line. We show the QTP value for each simulation iteration with blue dots and the loess smoothing with the blue line. i–l) Logistic generalized additive model probability for the QTP-binary response variable with admixture date (T_admix) and median pairwise F_ST as predictor variables (parameters restricted to the historical range described above). The gray dots are unique combinations of simulation parameters placed in the space of predictor variables. Vertical dotted lines in plots e–l) show the median pairwise F_ST values at the approximate Iron Age (0.008) and Bronze Age (0.013) periods.