A long-held assumption faces a major challenge — could life on Earth have emerged not once, but twice?
August 6, 12:30
An international team of scientists has released a study proposing that bacteria and archaea may have each made the transition from non-living matter to living cells independently. In other words, life on Earth might have begun twice. Science Alert reported on the findings.
Bacteria and archaea are the two major branches of living organisms. The research found that enzymes from these two groups, even when responsible for identical chemical reactions, appear to come from different origins. One of the co-authors,
William Martin, says that 'the genetic code may have arisen once, but life itself — twice.'
The last common ancestor of all current cells is known as LUCA. According to the researchers' estimates, LUCA possessed enzymes for only about half of its metabolic reactions. The other half was driven by natural chemical processes involving metals. In Earth's early history, the researchers argue, hydrothermal vents supplied metal catalysts that played this supporting role.
The study also draws attention to phosphite, a phosphorus compound found naturally in hydrothermal vents. In laboratory experiments, phosphite combined with palladium produced the needed reactions without ATP or enzymes. Modern cells rely on ATP as their main energy currency. The authors stress, however, that this remains a hypothesis requiring further investigation.
These discoveries put traditional ideas about the origin of life on Earth in question, while opening new possibilities for studying the evolution of living organisms. The findings could reshape our understanding of evolutionary history and influence future research in both biology and astrophysics. If life really did start twice on Earth, it would point to multiple evolutionary routes — and that has implications not only for our own planet, but for the search for life elsewhere in the universe.