Range: ±170 Mya
||Emelyanov VV. Mitochondrial connection to the origin of the eukaryotic cell. Eur J Biochem. 2003 Apr270(8):1599-618. p.1604 left column 2nd paragraphPubMed ID12694174
|| Emelyanov, V.V. (2001) Rickettsiaceae, rickettsia-like endosymbionts, and the origin of mitochondria. Biosci. Rep. 21, 1–17. p.12 top paragraphPubMed ID11508688
||P.1604 left column 2nd paragraph: "Dating of the divergence of Rickettsiaceae and mitochondria, i.e. effectively the mitochondrial origin, was recently attempted by using the sequences of Cpn60, a ubiquitous, conserved protein with clock-like behavior."
||P.1604 left column 2nd paragraph: "Timing of the appearance of eubacterial genes in eukaryotic genomes is another way to attempt to distinguish between different hypotheses about the origin of the pro-eukaryotic genome. Available data of this kind are rather controversial. On the one hand, Feng et al. [ref 2, BNID 113206] showed that archaeal genes appeared in Eukarya about 2.3 billion years ago (Bya) while eubacterial genes appeared 2.1 Bya. It was suggested that both estimates relate to the same event, fusion between an archaebacterium and a eubacterium, and the shift in the appearance time of bacterial genes to the present day was merely due to involvement in the analysis of mitochondrial and α-proteobacterial sequences. The above small difference would thus just reflect a more recent endosymbiotic event [primary source]. On the other hand, Rivera et al. [ref 7] argued that archaeal (informational) genes were acquired by Eukarya in a single, very ancient event, whereas acquisitions of eubacterial (operational) genes were scattered along the timescale [ref 7]. One may realize here that most eubacterial genes appeared in eukaryotes during both the fusion and subsequent endosymbiotic event, while others were derived from various bacterial groups more recently, when the true eukaryotes capable of endocytosis emerged (see below). Dating of the divergence of Rickettsiaceae and mitochondria, i.e. effectively the mitochondrial origin, was recently attempted by using the sequences of Cpn60, a ubiquitous, conserved protein with clock-like behavior. Rickettsiaceae and mitochondria were shown to have emerged 1.78 ± 0.17 Bya [primary source], i.e. significantly later than the appearance of eubacterial genes in eukaryotic genomes dated in the above-cited work [ref 2] using a comparable approach." Please note: "emerged" in bottom-most sentence should probably be "diverged".