Protocode mats and living membranes: A new hypothesis for the origin of the standard genetic code

The standard genetic code (SGC) maps 64 codons to 20 amino acids and three stop codons. The Combinatorial Fusion Cascade (CFC), introduced in 2020, identified three combinatorial rules that reproduce all 64 codon-amino acid assignments through a cascade of eight initial complementary pairs, four protocodes, and the SGC. Here we advance the CFC programme on several fronts not made explicit in the original publications. First, we draw a sharp distinction between the fusion rules - objective structural properties of the standard code table, readable independently of any historical assumption - and the CFC as a hypothesis about how these rules arose; the rules are facts, the cascade is one mechanism that could have generated them. Second, we formalize the rules as deterministic operators on the bases that regenerate all 64 assignments, and we introduce an entropy rank of codons under which the three cascade stages emerge as nested levels (4 ⊂ 16 ⊂ 64), making the increase of codon entropy along the cascade explicit. Third, we give an explicit set of falsifiable predictions, separating those testable now from those awaiting suitable methods: Mendeleev-like positions for amino acids that entered or left the code (canavanine as X2; the recently reported archaeal code in which UAG encodes pyrrolysine matching the predicted occupancy of X1); the presence of aromatic amino acids (Phe, Tyr) from the inception of the code; and a temporal ordering in which sulfur chemistry was integrated only after the initial complementary pairs were established (cysteine at the protocode stage, methionine after fusion). Fourth, and most centrally, we propose that the code arose not in lipid vesicles but in protocode mats - layered RNA-peptide communities on catalytic mineral surfaces, in which amphiphilic RNA-peptide complexes serve at once as code carriers and as a surface-associated boundary rather than a closed lipid container. This setting does not require a lipid membrane while the code itself was forming and yields a falsifiable geochemical roadmap, the temporal order of the cascade constraining the sequence of environments in which it unfolded.