Study Suggests Life on Earth Evolved Twice, Not Once

A new study published in Science Advances proposes that life on Earth may have originated twice, independently evolving from a common ancestor known as LUCA (last universal common ancestor). The research, led by evolutionary biologist William Martin at the University of Düsseldorf, analyzed metabolic genes in modern bacteria and archaea to reconstruct the evolutionary history of core metabolism. The team found that bacteria and archaea share some enzymes with LUCA but also evolved unique enzymes to replace metal-catalyzed reactions, indicating two separate transitions from LUCA to free-living cells. This challenges previous theories that one lineage evolved from the other. The study also suggests that LUCA was not fully alive, relying on environmental metals and organic molecules for about half of its metabolic reactions. Key findings include the role of phosphite and palladium in energy storage as ADP, a precursor to ATP, and the independent evolution of ribosomal proteins in bacteria and archaea. The research has sparked debate among scientists, with some questioning the complexity of LUCA and the definitiveness of the conclusions. The study was co-authored by researchers from the University of Düsseldorf, University of Canterbury, and University of Ottawa, among others.