As Earth calms, hydrogen becomes scarce. The cyanobacteria (the blue-greens, wiliest of the microbes), pioneer the intranet approach: inside themselves, they link together two photosystems. This gives cyanobacteria enough energy to split tightly knit water molecules and procure hydrogen.
Waste Not. Great innovations are often characterized by unexpected novelties and unimaginable results. This power-plant technique of harvesting hydrogen also produces highly toxic waste, oxygen, which poisons other anaerobic microbes while opening new and diverse paths for oxygen-breathing biota.