bio

Last universal common ancestor

The organism every surviving lineage on Earth traces back to — not the first organism, but the last branch point still legible in all our genomes. Reconstructing LUCA from widely shared genes yields a portrait of an anaerobic, heat-loving, hydrogen-fed organism using iron-sulfur clusters, which is often cited in support of a vent origin. The criticism lands too, though: LUCA was already a sophisticated organism, far downstream of the earliest prebiotic steps.