LUCA is dated to about 4.2 Ga by phylogenomic analysis
Moody and colleagues published a phylogenomic reconstruction placing the last universal common ancestor at approximately 4.2 billion years ago and inferring a genome of roughly 2.5 megabases coding on the order of 2,600 proteins, with an anaerobic, probably acetogenic metabolism and an early form of immune defence against viruses. Two implications matter for this Journey. The first is that if the estimate holds, LUCA existed within a few hundred million years of the Moon-forming impact, leaving very little time for the chemistry that preceded it. The second is that LUCA is inferred to have been complex and ecologically embedded, so it was not the first cell and cannot mark the origin of life. Molecular dates of this age carry large model dependencies and this one is not a settled result.
Uncertain — sources disagree, or the dating is contested. Stated here, not resolved.
Subjects
- LUCA — the last universal common ancestor · species · not located
- Molecular clock dating · process · not located
Evidence
Partly verified — Core facts are sourced; some optional detail is deliberately absent.
The nature of the last universal common ancestor and its impact on the early Earth system
Supports the c. 4.2 Ga age estimate for LUCA and the inferred genome size and metabolic character. Deliberately cited without volume or page numbers, which were not confirmed. V55 verification basis: this session had no network access to any source — WebFetch was egress-blocked and the WebSearch budget was exhausted — so the cited work was not retrieved and its pagination was not re-checked.
Nature Ecology and Evolution · 2024 · Partly verified
Moody, E. R. R. et al., Nature Ecology and Evolution (2024)