Editing Last universal common ancestor (section)

{{Short description|Most recent common ancestor of all current life on Earth}}
{{Redirect|LUCA|other uses|Luca (disambiguation){{!}}Luca}}
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[[File:Phylogenetic tree of life 1990 LUCA.svg|thumb|upright=1.75|[[Phylogenetic tree]] linking all major groups of living organisms, namely the [[Bacteria]], [[Archaea]], and [[Eukaryote|Eukarya]], as proposed by Woese et al 1990,<ref name="Woese Kandler Wheelis 1990"/> with the last universal common ancestor (LUCA) shown at the root]]

The '''last universal common ancestor''' ('''LUCA''') is the hypothesized common ancestral [[Cell (biology)|cell]] from which the [[Three-domain system|three domains of life]],<!--<ref name="Woese Kandler Wheelis 1990"/>--> the [[Bacteria]], the [[Archaea]], and the [[Eukarya]] originated. The cell had a [[lipid bilayer]]; it possessed the [[genetic code]] and [[ribosome]]s which [[Translation (biology)|translated]] from [[DNA]] or [[RNA]] to [[protein]]s. Although the timing of the LUCA is not able to be definitively constrained, most studies suggest that the LUCA existed by or prior to 3.5 billion years ago, and possibly as early as 4.3 billion years ago or earlier. The nature of this point or stage of divergence remains a topic of research.<!--<ref name="Harold_2014"/>-->
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All earlier forms of life preceding this divergence and all extant organisms are generally thought to share [[common ancestry]]. On the basis of a formal statistical test, this theory of a universal common ancestry (UCA) is supported versus competing multiple-ancestry hypotheses.<!--<ref name="Theobald-2010"/>--> The [[first universal common ancestor]] (FUCA) is a hypothetical non-cellular ancestor to LUCA and other now-extinct sister lineages.
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Whether the genesis of [[virus]]es falls before or after the LUCA–as well as the diversity of extant viruses and their hosts–remains a subject of investigation.
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While no fossil evidence of the LUCA exists, the detailed biochemical similarity of all current life (divided into the three domains) makes its existence widely accepted by biochemists. Its characteristics can be inferred from [[phylogenetic bracketing|shared features of modern genomes]]. These genes describe a complex life form with many [[co-adapted]] features, including [[transcription (biology)|transcription]] and [[translation (biology)|translation]] mechanisms to convert information from [[DNA]] to [[mRNA]] to [[protein]]s.
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