Life Twice Over: Earth's Origins May Trace To One Lifeless Forebear

Analysis of chemical reactions in single-celled organisms suggests that life on Earth may have emerged twice. Researchers propose that bacteria and archaea evolved independently from a common non-living precursor rather than descending from a single shared living cell. This hypothesis challenges the traditional theory of a Last Universal Common Ancestor (LUCA) for all existing life forms.

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Bacteria under microscope

Methodology of Evolutionary Reconstruction

The study is based on an analysis of metabolic processes in unicellular organisms. Researchers examined internal cellular chemical reactions to trace the evolutionary trajectories of bacteria and archaea, the two largest groups of microorganisms.

The method involves identifying common and unique biochemical signatures. The researchers posit that if fundamental cellular mechanisms differ significantly between these groups, it indicates parallel formation rather than a split from a single ancestral living organism.

Divergence of Bacteria and Archaea

The data indicate that bacteria and archaea diverged during the earliest stages of Earth's history. This separation resulted in the development of distinct cellular architectures and metabolic pathways.

These findings suggest that early life forms adapted to different environmental conditions independently.

Interpretive Boundaries and Limitations

The study does not provide a definitive answer regarding the exact mechanism of the origin of life. Because researchers rely on an analysis of existing organisms to reconstruct the past, the method remains indirect.

The current data do not identify the specific chemical compounds that served as the "non-living ancestor" or the precise conditions under which this occurred. The hypothesis of two separate origins requires further verification through the discovery of transitional forms or simulations of early Earth chemistry.

While the work refines the understanding of early evolution, it does not establish multiple origins as an indisputable fact—it offers a theoretical alternative to the single-ancestor cell model. Further details are available in the original study.