AUTOCATALYTIC REPLICATION OF IjOLYMERS

We construct a simplified model for the chemistry of molecules such as polypeptides or single stranded nucleic acids, whose reactions can be restricted to catalyzed cleavage and condensation. We use this model to study the spontaneous emergence of autocatalytic sets from an initial set of simple building blocks, for example short strands of ammo acids or nucleotides. When the initial set exceeds a critical diversity, autocatalytic reactions generate large molecular species in abundance. Our results suggest that the critical diversity is not very large. Autocatalytic sets formed in this way can be regarded as primitive connected metabolisms, in which particular species are selected if their chemical properties are advantageous for the metabolism. Such autocatalytic sets may have played a crucial role in the origin of life, providing a bridge from simple molecular species to complex proteins and nucleic acids. Many of our results are experimentally testable.