Departure from randomness: Evolution of self-replicators that can self-sort through steric zipper formation.

Darwinian evolution of self-replicating entities most likely played a key role in the emergence of life from inanimate matter. For evolution to occur, self-replicators must (1) have structural space accessible to them, (2) occupy only part of it at any time, and (3) navigate it through mutation and selection. We describe a system of self-replicating hexameric macrocycles formed upon the mixing of two building blocks and occupying a subset of possible sequences. Specific interactions, most likely through steric zipper formation, favor a hexamer sequence where the two blocks alternate. Under different replication-destruction regimes, distinct replicator mutants are selected. With non-selective destruction (via outflow), the fastest replicators dominate. With chemically mediated, selective destruction, a mutant that balances replication speed and resistance to reduction by steric zipper formation becomes dominant. This system demonstrates a rudimentary form of Darwinian evolution, where replicators adapt to changing selection pressures through mutation and selection.