The Nature of the Last Common Ancestor

摘要: Until the late 1970s cellular evolution was assumed to be a continuous, unbroken chain of progressive transformations that begun with emergence life itself and continued until endosymbiotic origin eukaryotes marked major biological discontinu-ity. This scheme challenged when comparison small subunit ribosomal RNA (16/ 18S rRNA) sequences led construction trifurcated, unrooted tree in which all known organisms can grouped one three monophyletic cell lineages, i.e., domains Bacteria (eubacteria), Archaea (archaeabacteria), Eucarya (eukaryotes). Information from single molecular marker does not necessarily yield precise reconstruction evolutionary processes, but as shown by numerous phylogenies constructed other genes such those encoding polymerases, elongation factors, F-type ATPase subunits, heat-shock proteins, identification lineages is an artifact based solely upon reductionist extrapolation information derived rRNA tree, true reflection ancient trifurcation.