Before revision: This also forced the surviving anaerobes to adapt a symbiotic life among aerobes ( who would have consumed free oxygen to create pockets of anoxia, where anaerobes can thrive), which might have paved way for the long-term endosymbiosis between anaerobic archaea and aerobic eubacteria (which evolved into mitochondria) that enabled eukaryotes to evolve.
After revision: This also forced the surviving anaerobes to adapt a symbiotic life among aerobes ( whose colonies would sometimes consume enough free oxygen to create pockets of hypoxiaeither live only in anoxic waters and deep sea oxygen minimum zones, or where anaerobes can thrive), which might have paved way for the long-term endosymbiosis between anaerobic archaea and aerobic eubacteria (which evolved into mitochondria) that enabled eukaryotes to evolve.