On one single occasion, here on earth, bacteria gave rise to eukaryotes. There is nothing in the fossil record, or in phylogenetics, to suggest that complex life actually arose repeatedly, but that only one group, the familiar modern eukaryotes, survived. On the contrary, the monophyletic radiation of eukaryotes suggests their unique origin was dictated by intrinsic physical constraints which had little if anything to do with environmental upheavals such as the Great Oxidation Event.
