Study Dates Last Universal Common Ancestor to 4.2 Billion Years Ago
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A molecular-clock analysis places the last universal common ancestor of all cellular life at 4.2 billion years ago, within a range of 4.09 to 4.33 billion years. The estimate, published in Nature Ecology & Evolution, pushes the origin of life deeper into Earth's Hadean eon. It does not date the first life, only the most recent population shared by all living organisms.
Key Facts
- The last universal common ancestor (LUCA) is estimated at 4.2 billion years ago, with a preferred range of 4.09 to 4.33 billion years.
- The estimate comes from a molecular-clock analysis using five ancient gene duplications, not from a fossil.
- The study was published in Nature Ecology & Evolution in 2024.
- LUCA is not the first life; other contemporary lineages likely existed but left no sampled cellular descendants.
The Molecular Clock
Researchers used paralogues—genes duplicated before LUCA—to anchor the evolutionary timeline. Five ancient gene duplications provided the calibration points for the molecular clock. The analysis integrated genes, fossils, and isotope constraints to produce the 4.2-billion-year estimate. The preferred model range spans 4.09 to 4.33 billion years ago.
LUCA's Place in Evolution
All cellular organisms share related translation machinery, ATP as an energy currency, and a nearly universal genetic code. These commonalities support descent from a shared population before the bacterial and archaeal split. Eukaryotes, including animals, plants, and fungi, arose later from within that ancient history. LUCA was likely a population, not a single individual or the only organism alive at the time.
Implications for Life's Origin
If LUCA lived 4.2 billion years ago, the origin of life must be older still. The estimate does not specify how much older, because extinct lineages cannot be reconstructed from modern genomes. The 2024 study depicts other contemporary lineages that left no sampled cellular descendants. Some of those lineages may have transferred genes into LUCA's descendants before disappearing.
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Study Dates Last Universal Common Ancestor to 4.2 Billion Years Ago
