The emergence of triadic, unidirectional communication in biology

All living cells rely on the same remarkable system: information flows from DNA to RNA to protein, always in that direction, never in reverse. This triadic, unidirectional architecture - the Central Dogma of molecular biology - is universal across all known life, yet no definitive theoretical explanation for its existence has ever been given. Why three? Why this direction and no other?

This paper presents an informational framework demonstrating that triadic, unidirectional communication is not a contingent biochemical accident, but a logical inevitability. When any communication system is subjected to just two constraints - (1) unique modes of communication, and (2) non-identical paths of communication - the result is always a three-node, unidirectional architecture. The informational roles of DNA, RNA and protein map precisely onto this abstract structure.

To validate this framework, computer simulations were performed on 100 initially random directed networks (Erdős-Rényi, N=12, p=0.15). Under the sequential application of both constraints, triadic unidirectional chains emerged in more than one in four simulations from a completely undirected starting topology. Strikingly, networks in which every node carries the same functional role - analogous to a pure RNA World - were entirely eliminated, suggesting that total functional homogeneity is not a viable communication architecture.

These findings indicate that the Central Dogma is the physical instantiation of a more general, substrate-independent law of information transfer, here termed the Non-Physical Communication Architecture (NPCA). This framework shifts the origin of life from a problem of chemistry to a problem of constrained communication, and raises the tantalising possibility of multiple independent origins of life - which, by virtue of their identical architectures, would be indistinguishable from one another.

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Email: philip@rushtonresearch.com