Differences in taxon ranks between South African samples and human microbiome project. A, B) Oral microbiome structure varies among the KhoeSan. Each of the above stacked bar plots illustrates the relative abundance (y-axis) of the most abundant oral microbiota at the A) genus, and B) species levels for each of the 15 KhoeSan individuals (x-axis). Relative abundance was measured as the fraction of high-quality reads that were recruited to a microbial genome of a particular taxonomic rank using conservative recruitment settings (Methods). Only the nine most abundant groups for each taxonomic level are illustrated for visualization purposes, with the remaining taxa being grouped into the ‘Other’ category. C) KhoeSan (red) and healthy North American (blue) saliva microbiomes differ in their community structure. In this bar plot, the normalized relative abundance, which is a taxon’s median relative abundance detected within a population divided by the maximum relative abundance detected within a population, is shown for bacterial genera that are detected in either of the two populations. Genera are ordered by their median relative abundance across the KhoeSan. Notable differences between the populations are those where the taxon is abundant in the KhoeSan and effectively undetected in the North Americans, especially Rothia.