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“One Origin of the Genetic Code, but Two Origins of Life”: Scientists Reveal the Ancient Evolutionary Split That Gave Rise to All Life on Earth
An international research team has uncovered how LUCA, the last common ancestor of all life on Earth, split into the first two branches of organisms—bacteria and archaea—allowinglife to thrive innew conditions and spread to other biomes.
Scientists from the Institute of Molecular Evolution at Heinrich Heine University Düsseldorf (HHU) led the research, revealing their findings in a recent paper published in Science Advances, investigating these early cells’ metabolisms.
The team discovered that the chemical reactions and energy sources behind these two types of cells told unique stories of separate evolutions, in new work that sheds light on the primordial processes that gave rise to some of Earth’s first free-living cells.
Life on Earth Begins
Roughly four billion years ago, life on Earth emerged as the first cells formed, most likely at hydrothermal vents, before evolving to explore new biomes.
“We would see two very different kinds of cells emerging, pioneer bacteria and pioneer archaea, making their first attempts at life outside the confines of a hydrothermal vent,” said lead author Natalia Mrnjavac, a biologist at the University of Düsseldorf.
The new study investigated protein structures, chemical reactions, and genomes involved in the evolution of these early free-living cells.
“These comparisons are giving us unprecedented insights into the phase of evolution when metabolism catalysed by enzymes was arising from spontaneous reactions catalysed by metals in the Earth’s crust,” said senior author William Martin, a Düsseldorf biologist.
Metabolism and Evolution
Among the new work’s major findings is a consideration of the entire set of 420 chemical reactions involved in metabolism that produce amino acids, RNA bases, and vitamins from the raw materials of hydrogen, ammonia, and carbon dioxide.
These reactions are preserved for modern researchers inside the genetic code, allowing the team to make a surprising discovery: about half of LUCA’s reactions were catalyzed by environmental metals instead of enzymes produced by the organism itself.
“Metals that naturally occur in hydrothermal vents can replace a surprisingly large number of enzymes in metabolism,” said co-author Harun Tüysüz, an inorganic chemist from the Max-Planck-Institut für Kohlenforschung and the IMDEA Materials Institute in Madrid.
In this study, the team reconstructed catalysis evolution from metal-only to a metal-enzyme hybrid present in LUCA, and finally to the divergence of the bacterial and archaeal lineages. This evolution helped life move on from the hydrothermal vents inhabited by the first cells by replacing the inorganic catalysts provided by that environment with new enzymes.
“We can see cases where the ancestors of bacteria and archaea independently evolved structurally distinct enzymes to catalyse the same essential metabolic reaction,” Mrnjavac explained, adding that “such parallel inventions could have paved the way to the independent emergence of free-living bacteria and archaea.”
The Energy for Life on Earth
A primary question involves what supplied the energy driving metabolic reactions in early life on Earth. A compound named ATP is the primary metabolic driver in most organisms today, but it comes from enzymes and is not present in hydrothermal vents. The researchers identified a new energy source in palladium, a natural catalyst used by chemists and also plentiful in hydrothermal vents.
“When we react phosphite, a form of phosphorus that naturally occurs in hydrothermal vents, with organic compounds, we get metabolic phosphorylation reactions overnight in water. Phosphite and palladium replace ATP and enzymes; it’s amazing, and it makes early evolution a lot easier to grasp,” Schlikker said.
Understanding the interconnection between so many reactions presents a significant mathematical challenge. For this reason, the team included not just biologists, but network scientists tasked with ordering the reactions by their complexity, which the researchers hoped would indicate the sequence in which they evolved. Using a machine learning algorithm, the team discovered that a clear order did appear to exist.
“The new data leave only one conclusion,” Martin concluded. “The bacteria and archaeal lineages made the transition to the free-living state independently. Only free-living cells are alive.”
“Let’s call it by name,” Martin added. “We are looking at one origin of the genetic code, but two origins of life.”
The paper, “Intermediate Stages in the Origin of Metabolism at a Phosphorylating Hydrothermal Vent,” appeared in Science Advances on August 5, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org.
