nucleation

THEORY-1201: Normalized stem length is not a clock of gene acquisition time: it is set mainly by factors other than when a gene was acquired, such as adaptation to the new cell after acquisition, so relative timings of eukaryogenesis drawn from stem lengths alone are not supported

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Properties5
StatusProposed
Tagsendosymbiosis, natural-sciences
SourceLIT-1558 — Dominant contribution of Asgard archaea to eukaryogenesis
ExtendsTHEORY-1101 — Tobiasson, Luo, Wolf and Koonin find, on 5,850 eukaryotic gene stems, that normalized stem length does not behave as a clock of acquisition time: alphaproteobacterial stems are longer than Asgard ones for the 70% of stems below 0.3 and shorter only above 0.35, oxidative-phosphorylation genes presumed acquired together vary by more than two orders of magnitude, and information-processing genes have short stems; they conclude that even normalized stem lengths are set primarily by factors other than acquisition time, at least over the long timescales analysed, and suggest that adaptation after acquisition lengthens stems
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 conclude that “even normalized stem lengths are determined primarily by factors other than the gene acquisition time”, and suggest post-acquisition adaptation as one such factor.

Where the evidence stands

What the paper shows, and what it does not, is THEORY-1101, Active, which this entry extends: that entry is the reading, this one the thesis. The promote_when above is THEORY-1101’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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