Study Suggests Bacteria and Archaea May Have Arisen Independently

A study published in 2026 challenges the long-standing view that all cellular life descends from one free-living organism known as the last universal common ancestor, or LUCA.

Researchers traced ancient chemical reactions preserved in the metabolism of modern bacteria and archaea, the two primary domains of single-celled life.

The analysis found that core metabolic pathways in bacteria and archaea show fundamental differences in how they process energy and carbon.

These differences are deep enough that the authors argue they likely originated in distinct populations of protocells rather than diverging from a single, already complex cell.

The proposed scenario envisions a prebiotic chemical system — sometimes called a progenote — that gave rise to two separate lineages capable of independent replication and metabolism.

If confirmed, the finding would mean the tree of life has two trunks at its base rather than one, reshaping models of early evolution.

The work relies on comparative biochemistry and phylogenetic reconstruction, methods that carry inherent uncertainties when looking back more than 3.5 billion years.

Further research will be needed to test whether the observed metabolic splits reflect independent origins or extreme divergence after a single origin.