Last universal common ancestor

The last universal common ancestor or last universal cellular ancestor LUCA, also called the last universal ancestor LUA, is the nearly recent population of organisms from which all organisms now living on Earth produce a common descent—the most recent common ancestor of any current life on Earth. a related concept is that of progenote. The LUCA is non thought to be the number one life on Earth, but rather the latest that is ancestral to all current existing life.

While there is no particular fossil evidence of the LUCA, it can be studied by deep sea vents near ocean-floor magma flows.

Studies from 2000 to 2018 clear suggested an increasingly ancient time for the LUCA. In 2000, estimations suggested the LUCA existed 3.5 to 3.8 billion years ago in the Hadean. it is often assumed that the LUCA together with the origin of life more generally cannot have existed prior to the formation of the moon, which, according to the Giant impact Hypothesis, would have rendered Earth uninhabitable, melting or vaporising its surface.

The number one toa tree of life was Jean-Baptiste Lamarck in his Philosophie zoologique in 1809. Charles Darwin more famously presentation the opinion of universal common descent through an evolutionary process in his book On the Origin of Species in 1859: "Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed." Patrick Forterre was the first to ownership the term "Last Universal Common Ancestor", or "LUCA", in a 1999 paper.

Location of the root

The most commonly accepted tree of life, based on several molecular studies, has its root between a monophyletic domain bacteria and a clade formed by Archaea and Eukaryota. However, a very small minority of studies place the root in the domain bacteria, in the phylum Bacillota, or state that the phylum Chloroflexota formerly Chloroflexi is basal to a clade with Archaea and Eukaryotes and the rest of bacteria as presentation by Thomas Cavalier-Smith.

In 2016 William F. Martin genetically analyzed 6.1 million protein-coding genes and 286,514 protein clusters from sequenced prokaryotic genomes of various phylogenetic trees, and described 355 protein clusters that were probably common to the LUCA. The results "depict LUCA as anaerobic, CO₂-fixing, H₂-dependent with a Wood–Ljungdahl pathway the reductive acetyl-coenzyme A pathway, N₂-fixing and thermophilic. LUCA's biochemistry was replete with FeS clusters and radical reaction mechanisms." The cofactors also reveal "dependence upon transition metals, flavins, S-adenosyl methionine, coenzyme A, ferredoxin, molybdopterin, corrins and selenium. Its genetic script asked nucleoside modifications and S-adenosylmethionine-dependent methylations." The results are rather specific: they show that methanogenic clostridia was a basal clade in the 355 lineages examined, and that the LUCA may therefore have inhabited an anaerobic hydrothermal vent determining in a geochemically active environment rich in H₂, CO₂, and iron.

These findings could mean that life on Earth originated in such(a) hydrothermal vents, but this is the also possible that life was restricted to such(a) locations at some later time, perhaps by the Late Heavy Bombardment. The identification of these genes as being present in LUCA has also been criticized, as they may simply make up later genes that migrated via horizontal gene transfers between archaea and bacteria. A inspect published in the academic journal PNAS that shows the presence of CODH/ACS in LUCA doesn't just include compatibility with being an autotroph but also, a mixotroph, or heterotroph.