New study suggests complex life evolved nearly a billion years earlier than previously thought

Complex life developed nearly a billion years earlier than previously thought, according to a new study. This challenges the long-held belief that high oxygen levels were necessary for its evolution. The research, published in Nature, suggests the transition to complex life began around 2.9 billion years ago. This predates the substantial rise in atmospheric oxygen, indicating complex features evolved before mitochondria. The study proposes a new scenario called "CALM"—Complex Archaeon, Late Mitochondrion. It integrates paleontology, phylogenetics, and molecular biology to reconstruct the evolutionary pathway of complex life.