Overview
- Researchers infer that the archaeal lineage leading to the eukaryotic nucleus diverged about 3.05–2.79 billion years ago.
- The bacterial lineage that became mitochondria branched later, roughly 2.37–2.13 billion years ago, coinciding with the first major rise in atmospheric oxygen.
- Gene-family duplications of archaeal origin, including actin and tubulin, predate mitochondrial endosymbiosis, indicating early assembly of cytoskeletal and nuclear systems.
- Most bacterial-origin gene duplications appear after the mitochondrial merger, suggesting a later expansion of metabolic and cellular functions.
- The Bristol-led team’s CALM framework combines broad sequence sampling with fossil calibrations to time these events, challenging models that place mitochondria at the start of eukaryotic complexity.