LAUSR

In this hypothesis article, we propose that the timing of the evolution of oxygenic photosynthesis and the diversification of cyanobacteria is firmly tied to the geological evolution of Earth in the Mesoarchaean to Neoarchaean. Specifically, the diversification of species capable of oxygenic photosynthesis is tied to the growth of subaerial (above sea-level/terrestrial) continental crust, which provided niches for their diversification. Moreover, we suggest that some formerly aerobic bacterial lineages evolved to become anoxygenic photosynthetic as a result of changes in selection following the reintroduction of ferruginous conditions in the oceans at 1.88 GYa. Both conclusions are fully compatible with phylogenetic evidence. The hypothesis carries with it a predictive component-at least for terrestrial organisms-that the development and expansion of photosynthesis species was dependent on the geological evolution of Earth.