Life on Earth May Have Originated Twice: A Radical New Study on Bacteria, Archaea, and the Pre-Cellular Ancestor LUCA

Two Independent Origins, Not One Trunk

Led by researchers at Heinrich Heine University Düsseldorf, the team analyzed 420 core metabolic reactions across bacteria and archaea — the two most fundamental domains of life. Their key finding: the enzymes catalyzing these essential reactions are not conserved between bacteria and archaea . Instead, the ancestors of each lineage independently evolved structurally distinct enzymes to perform the same metabolic functions, meaning each lineage made the transition to a free-living state separately.

"The new data leave only one conclusion," senior author William Martin told multiple outlets. "We are looking at one origin of the genetic code, but two origins of life" .

Redefining LUCA: A Pre-Cellular, Metal-Dependent Entity

The study dramatically revises the concept of the Last Universal Common Ancestor (LUCA). Far from being a free-living cell, LUCA is reconstructed as a pre-cellular, non-free-living entity that existed in hydrothermal vent environments. LUCA possessed enzymes for only about half of the 420 core metabolic reactions studied. The other half was catalyzed by metals naturally present in the environment, such as iron, nickel, and cobalt .

The team reconstructed four stages of early catalysis: (1) metal-only reactions, (2) a metal-enzyme hybrid within LUCA, followed by divergent evolution toward (3) the bacterial ancestor and (4) the archaeal ancestor . This gradual assembly of metabolism from inorganic parts provides a new framework for how life could emerge from geological processes.

Before ATP: Phosphite and Palladium as an Ancient Energy Source

Modern cells use ATP (adenosine triphosphate) as their universal energy currency, but ATP is a complex molecule requiring sophisticated enzymes to produce. The study, drawing on earlier preprint work from the same group and independent research , identifies a plausible prebiotic alternative.

Phosphite (HPO₃²⁻), a reduced form of phosphorus that occurs naturally in serpentinizing hydrothermal vents, reacts with organic compounds in the presence of native palladium – a metal catalyst also deposited in those same vents. This reaction drives metabolic phosphorylation reactions in water at temperatures between 25–100°C, effectively replacing the need for ATP and complex enzymes .

"Phosphite and palladium replace ATP and enzymes; it's amazing, and it makes early evolution a lot easier to grasp," said co-author Manon Schlikker .

Reframing the Tree of Life

The traditional tree of life places LUCA as the single trunk from which all life branches. This study suggests a fundamentally different topology: two separate trunks (bacteria and archaea) that diverged at the roots, before they were technically alive . The common ancestor was not a free-living cell but a pre-cellular entity that later gave rise, independently, to the two living lineages.

Implications and Context

This study fits within a larger body of recent research that has deepened understanding of LUCA. A 2024 study in Nature Ecology & Evolution estimated that LUCA lived around 4.2 billion years ago and possessed a genome as large as some modern bacteria, with a rudimentary immune system . The new Science Advances paper builds on that understanding, but shifts the focus from LUCA as a common ancestor to LUCA as a shared pre-cellular stage from which life arose twice.

The findings do not challenge the unity of the genetic code (which suggests a single origin for the information system of life), but they do propose that the transition to cellular, free-living life happened separately in the two great microbial lineages .

Key Takeaways

• Dual origin: Bacteria and archaea likely evolved free-living states independently, not from a single free-living ancestor .
• LUCA redefined: The Last Universal Common Ancestor was a pre-cellular, non-living entity whose metabolism was partly driven by environmental metals .
• Metals before enzymes: Iron, nickel, and cobalt catalyzed about half of core reactions before life had evolved its own enzyme toolkit .
• Phosphite-palladium energy: A natural chemical system in hydrothermal vents could drive crucial metabolic reactions before ATP existed .
• Tree of life revised: The classic single-trunk tree is replaced by a model with two deep independent branches emerging from a shared inorganic-origin phase .