Life on Earth Appears to Have Begun Not Once, but Twice, Scientists Say

A Double Origin for Life

According to НВ — Техно: According to a new study, Earth's earliest free-living cells may have come into existence on two separate occasions. An international research team now believes that bacteria and archaea each made the leap from relying on hydrothermal vents to surviving independently, even though their genetic codes share a single ancestral root. The findings, released on August 12 in ScienceDaily, focus on the metabolic workings of primordial cells and examine 420 distinct metabolic reactions.

How the Study Was Conducted

To piece together this ancient puzzle, the researchers analyzed the genomes and protein structures of modern bacteria and archaea. Their estimates suggest that LUCA-the last universal common ancestor of all cellular life-carried enzymes capable of driving roughly half of those 420 reactions. The remaining steps, the team proposes, could have been powered by naturally occurring metals found around hydrothermal vent environments.

Strikingly, the study uncovered cases where bacteria and archaea independently evolved structurally different enzymes to perform the same essential biochemical reactions. That points to a shared origin for these two microbial domains, yet separate evolutionary paths as each adapted to its own environmental pressures. The scientists also singled out phosphite as a plausible energy source for early cells, noting that in combination with palladium it can trigger reactions tied to metabolic phosphorylation.

To bring order to the data, the team devised a mathematical approach that arranged the 420 reactions in sequence from simplest to most complex. While every cell type may share a common genetic code, the transition to autonomous life probably unfolded separately within the bacterial and archaeal lineages. As a result, the study sketches an unexpected scenario for how life took hold on our planet.

These insights carry significant weight for our understanding of evolutionary history and could reshape ideas about how early cells responded to their surroundings. The evidence that bacteria and archaea achieved independence on their own underscores just how intricate the evolutionary processes were that produced life's vast diversity.

The work also opens new avenues for examining early cellular metabolism under conditions very different from today's. Additionally, it may inform future biochemistry and genetics research-particularly the search for life beyond Earth.