English: Proposed narrative for the cyanobacterial context of Earth's oxidation. Relative probability density distributions are shown for crown bacteria (purple), total group Cyanobacteria (red) and crown group Cyanobacteria (blue). This hypothesized history of cyanobacteria shows oxygenic forms arising from within a diversity of anoxygenic stem groups in the Archean (eon). A timeline of geological evidence shows that these dates are consistent with Mesoarchaean and Neoarchaean geochemical and morphological evidence of oxygenic photosynthesis).