First universal common ancestor

The first universal common ancestor (FUCA) is proposed to have been a non-cellular entity that was the earliest organism with a genetic code capable of performing biological translation of RNA molecules to protein formation through peptides synthesis. Its descendants would include the last universal common ancestor (LUCA) and, therefore, all modern cells. FUCA would also be the ancestor of ancient sister lineages of LUCA with no direct modern descendants, but may have transferred genetic material horizontally into the genomes of early descendants of LUCA.

FUCA is thought to have been composed of progenotes, ancient biological systems that would have used RNA for their genome and self-replication. By comparison, LUCA would have had a complex metabolism and a DNA genome containing hundreds of genes grouped into several gene families.

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