A Ribozyme Mass Extinction At The RNA-cellular Boundary And Its Potential Imprint On The Genetic Code

The transition from the RNA world to cellular life remains one of the least understood events in the history of biology.

This study proposes that geochemical changes approximately 3.9-3.8 billion years ago triggered a mass extinction of ribozymes – possibly the first extinction event on Earth – and that the genetic code bears the fingerprints of its survivors.

The argument draws on parallels with animal mass extinctions, where generalist species survive, dominate post-extinction ecosystems as disaster taxa, and shape subsequent evolutionary trajectories. Among small self-cleaving ribozymes, the hammerhead ribozyme accounts for approximately 91% of all ∼221,000 known sequences and is the only ribozyme that is found across all kingdoms of life.

The phylogeny of hammerhead ribozymes exhibits a star-like topology consistent with rapid post-bottleneck expansion, and its small size, ability to tolerate diverse chemical conditions, and broad substrate specificity suggest it was a resilient generalist feeder fitting as a disaster taxon.

Other families of ribozymes possibly survived in small, taxonomically isolated populations resembling relict species in ecological refugia. It is suggested that the body plans of surviving ribozymes seeded the primitive processes that would later become the genetic code, for example with RNA-degrading trinucleotides becoming stop codons, partitioning the trinucleotide space into signals of termination and translation.

This hypothesis proposes a reframing of the origin of the genetic code in part as an ecological legacy rather than a purely chemical inevitability.

A ribozyme mass extinction at the RNA-cellular boundary and its potential imprint on the genetic code, biorxiv.org

Astrobiology, Genomics,