Scientists Astonished: Did Life Arise on Earth Twice?

An international team of scientists led by biologists from Heinrich Heine University Düsseldorf has taken a fresh look at theories about the emergence of life on Earth. Science Advances According to a study published in the journal, the transition from nonliving matter to living organisms may have occurred independently in the two main branches of life—bacteria and archaea.

Biologist William Martin, one of the study’s authors, notes that some key enzymes in bacteria and archaea are not evolutionarily related. Therefore, the scientists suggest that although the genetic code may have had a single origin, free-living forms of life could have developed along two independent pathways.

During the study, the scientists analyzed the protein structures of key metabolic enzymes in bacterial and archaeal genomes. The results indicate that LUCA —the presumed common ancestor of all cells—had enzymes for only some metabolic reactions, while the remaining processes may have been carried out with the help of metals present in the environment at the time, possibly around hydrothermal vents.

The scientists also identified four stages in the development of catalysis during the formation of life. Initially, reactions depended on metals in the external environment. Later, protocells gradually developed their own enzymes, and eventually they no longer needed external catalysts. According to the researchers, it was after this stage that bacteria and archaea independently became free-living organisms.

Biologist Natalya Mrnyaivach notes that bacteria and archaea independently developed enzymes that perform the same functions but have completely different structures. This once again suggests that their evolutionary development may have occurred separately.

The researchers also proposed an alternative mechanism that could have replaced ATP in prebiological chemical processes. They found that phosphorylation reactions involving phosphite and palladium could occur naturally in water. According to the scientists, this discovery may simplify scientific understanding of the earliest stages of life and help answer new questions.