The last universal common ancestor
Every living thing on Earth descends from one organism — and it was already sophisticated.
- When
- Known to
- ± 120 million years
- Era
- Hadean
LUCA is not the first life but the most recent ancestor common to all surviving life. Reconciling gene phylogenies with the fossil and isotope record dates it to about 4.2 billion years ago, within a few hundred million years of the planet forming. It was no simple proto-cell: a complex anaerobic acetogen with a genome of perhaps 2,600 genes, an immune system, and a place in an ecosystem that already included other organisms now extinct. Life was therefore established, and diversifying, extraordinarily early.