Phylogenomic investigation indicates that the primary divergence between Archaea and Bacteria remains the deepest split in the Tree of Life, providing the essential framework for reconstructing the Last Universal Common Ancestor (LUCA). Dated to approximately 4.2 Ga, LUCA is characterized as a sophisticated anaerobic acetogen with a ~2.5 Mb genome and an early CRISPR-Cas immune system. The evolutionary history of specific marker genes, including photolyase and reverse gyrase, provides further constraints on LUCA’s physiological capabilities and its adaptation to early Earth environments. Following this ancestral state, the biosphere underwent a rapid expansion of metabolic repertoires. While LUCA utilized foundational pathways like Wood–Ljungdahl, more complex biogeochemical cycles achieved functional completeness across the Tree of Life by approximately 2 Ga. This trajectory suggests that the core of Earth’s metabolic diversity was largely finalized within the first two billion years through a combination of vertical inheritance and punctuated horizontal gene transfer, establishing a high-resolution timeline for the co-evolution of life and the planetary system.

The talk is part of the Computational Approaches to Early Evolution Workshop (April 20-24, 2026)