Variance in <i>f</i>_<i>4</i>-statistic Z-scores resulting from ascertainment and random site subsampling expressed as residual standard deviation of a linear trend fitted to a scatterplot of Z-scores on unascertained vs. ascertained data (abbreviated as “residual SE” and expressed in the same units as <i>f</i>_<i>4</i>-statistic Z-scores).

Results are shown for three classes of f4-statistics: f4(Africanx, archaic; Africany, Mediterranean/Middle Eastern), f4(Africanx, Africany; Africanz, archaic), and f4(African, Med/MEx; Med/MEy, Med/MEz). The following abbreviations are used for naming the f4-statistics classes: AFR, African populations; ARCH, archaic human individuals (Neanderthals and Denisovans); Med/ME or ME, Mediterranean and Middle Eastern populations. Results for ascertainment on variants common in Africans (either those having no detectable West Eurasian ancestry according to Fan et al. [67] or on all Africans in the SGDP dataset) are circled in red. Residual SE values for f4-statistic Z-scores lying not far from 0 (absolute Z-scores on all sites Fig 2.