Towards emergent replicators in a molecular artificial chemistry [article]

Thomas Young, University Of Canterbury
2017
All evolutionary systems, natural or artificial, are built from essentially the same three elements: variation, inheritance and selection. What then distinguishes the process of biological evolution by natural selection, which produces such impressive outcomes, from the relatively underwhelming results of artificial digital evolution? We focus on one aspect of this: the emergence of simple replicators from a lower-level foundation in an artificial chemistry. Previous work has either supplied a
more » ... andbuilt basic (or shortcut) replicator for evolution to work upon, or has provided direct support for replication in the chemistry itself. Our first research question concerns the relationship between heredity and selective pressure in a theoretical replicator. We construct a simple model of generalized evolution that shows complex and non-obvious emergent behaviour. We show by simulation that inheritance in this model is a target of evolution, and that it evolves under a range of conditions. The degree of inheritance is related to the predictability of environmental change, and the degree of inheritance is tuned by evolution to balance fitness and robustness. Fitness is maximized in unchanging environments where there is little penalty to reduced diversity, while a more diverse population is maintained in changing environments to provide robustness to environmental change. This balance emerges unprogrammed from the underlying model. Our second research question regards the practicality of realising replication in an artificial system. The investigation is founded on ToyWorld, a highly-modular artificial chemistry that allows us to explore the effect of different combinations of modules, such as for reactant or product selection, upon replicator formation. Our underlying hypothesis is that replicators can form from sequences of linked reaction cycles, where the stochiometry of the sequence is necessarily greater than one for replication. We first test the influence of two strategies to select reactants for a reaction, and [...]
doi:10.26021/3395 fatcat:yic7pl2a6naajcvw5xhe4zdkyi