Was the Mitochondrion Necessary to Start Eukaryogenesis?

The order in which novelties evolved during the process of eukaryogenesis is difficult to estimate because the fossil record is unhelpful in this case and organisms in which intermediate stages have been conserved are not known. Energy-based arguments claim that the mitochondrion must have preceded the origin of phagocytosis because it allowed for reserves of ATP that were necessary for establishment of the phagocytic apparatus and the increase...