nucleation

THEORY-1197: Eukaryogenesis involved one archaeal host lineage, of Asgard descent, and one bacterial endosymbiont, the alphaproteobacterial ancestor of mitochondria; the eukaryotic genes from other bacteria came by piecemeal gene transfer, not from further symbiotic partners

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Properties5
StatusProposed
Tagsendosymbiosis, natural-sciences
SourceLIT-1558 — Dominant contribution of Asgard archaea to eukaryogenesis
ExtendsTHEORY-1104 — In Tobiasson, Luo, Wolf and Koonin's constrained-tree survey of widespread eukaryotic protein families, Asgard archaea are the largest single prokaryotic source, with about half the likelihood weight in the best-resolved families and the lead in nearly every functional system, while Alphaproteobacteria contribute a small, coherent set centred on the mitochondrion and other bacteria about a third of families, scattered across functions with no pathway led by one donor except a narrow Myxococcota signal in nucleotide-sugar and nicotinate metabolism; the authors read this as one Asgard host lineage, one endosymbiont and piecemeal gene transfer rather than further symbioses
Bears onQUESTION-277 — When formerly autonomous partners come to depend on one another, which of mutual dependence, reproductive cohesion, the distribution of essential functions across genomes, the host's regulatory control and the alignment of selection does each route to dependence bring about, and which of them, alone or together, make the partnership a new evolutionary individual?

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Source

Tobiasson, Luo, Wolf & Koonin (2026), LIT-1558, read in full in NOTE-1242. The authors read their composition this way: “we obtained no indication of another symbiotic event contributing to eukaryogenesis”.

Where the evidence stands

What the paper shows, and what it does not, is THEORY-1104, Active, which this entry extends: that entry is the reading, this one the thesis. The promote_when above is THEORY-1104’s condition before the twenty-second status review promoted it, carried here unchanged, because it asks what would make the thesis true and not what the paper says.

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