EPSRC Network on Evolvability in Biology & Software Systems

Evolvability, Genetics & Development in Natural and Constructed Systems: Abstracts of the EPSRC Evolvability Network Symposium

Tewin Bury Farm Hotel, Hertfordshire, England, UK
26-28 August 2003

University of Hertfordshire Computer Science Technical Report 389
C. L. Nehaniv, P. J. Bentley & S. Kumar (Editors)

Evolvability of the Genotype-Phenotype Relationship in Populations of Self-Replicating Archeans

Evolvability of the Genotype-Phenotype Relationship in Populations of Self-Replicating Archeans


Algorithms Research Group & Adaptive Systems Research Group
University of Hertfordshire
Hatfield Hertfordshire AL10 9AB
United Kingdom

A.Nagy@herts.ac.uk, C.L.Nehaniv@herts.ac.uk

In Tierra-like systems, where programs written in an assembly language self-replicate and compete for resources the genotype-phenotype mapping is actually the execution of the code. The genotype is simply a sequence of instructions and the phenotype is the executed algorithm, the behaviour: computation of mathematical tasks, allocating memory, interacting with the environment. This mapping is constrained by the structure of the processor and this structure was fixed for an evolutionary scenario in previous systems.

Our approach here is to put the genotype-phenotype mapping under evolutionary control. We use a universal processor analogous to the universal Turing-machine and put the structural description of the actual processor into the organism's genome. The life-cycle of the organisms begins with building its actual processor. After successfull construction the organism can start executing instructions in the rest of its genome with the newly built processor. Since the definition of the processor is in the genome, it becomes subjected to mutations enabling evolution.

In this work we investigate the evolutionary development of the processor structures. Changes in the components (registers, stacks, queues), variations in instruction-set size and the redefinition of the instructions can be observed during experiments. We also consider the developmental process of the digital organisms and providing the capability of evolving multicellularity.