This chapter discusses the nature of life on ancient Earth before the evolution of oxygen production. It suggests that the Earth enjoyed an active and diverse biosphere well before the evolution of oxygen-producing cyanobacteria. This biosphere was fueled, mainly, by chemical compounds liberated during volcanism, underscoring again the importance of plate tectonics in shaping life on our planet. Geological evidence indicates that many of the processes that we have imagined were part of the early biosphere that was in place 3.5 billion years ago. These processes include methanogenesis, sulfate reduction, and decomposition of dead organic biomass, which was likely aided by a host of different fermenting bacteria. It seems likely, though, that this early biosphere was much less active than what we enjoy at present.