Scientists find evidence for two origins of life on Earth

Two origins of life on Earth have been proposed by scientists at the Institute of Molecular Evolution at Heinrich Heine University Düsseldorf. The research, published in Science Advances, suggests that free-living cells may have emerged independently twice. Approximately 4 billion years ago, Earth's surface was vastly different, potentially hosting two distinct forms of primitive cellular life: pioneer bacteria and pioneer archaea.

Researchers found evidence that the earliest cells used a chemical reaction network to produce basic life ingredients, powered by energy sources such as hydrogen gas, ammonia, and CO2. This metabolic network, consisting of 420 reactions, predates modern cellular metabolism. The enzymes responsible for these reactions are not conserved across bacteria and archaea, indicating that the last universal ancestor of all cells, LUCA, relied more on environmental metals than modern metabolism does.

The study reveals that early biochemical evolution was a hybrid of enzymatic and metal-catalyzed processes. Initially, reactions were driven entirely by metals, followed by LUCA where metals and enzymes collaborated. Subsequently, bacteria and archaea diverged, gradually replacing environmental catalysts with newly evolved enzymes.

Notably, the researchers identified instances where bacteria and archaea independently developed different enzymes to perform the same metabolic tasks, suggesting parallel evolutionary paths that may have enabled the two lineages to become less reliant on hydrothermal vent chemistry and eventually survive independently.