From Artificial Evolution to Artificial Life (De la evolución artificial a la vida artificial), tesis doctoral de Timothy John Taylor (1999)

'From Artificial Evolution to Artificial Life' es la tesis doctoral de Timothy John Taylor, Universidad de Edinburgo, 1999 (en inglés).

Resumen: Este trabajo aborda la siguiente cuestión: Cuáles son las consideraciones de diseño básicas para crear un modelo sintético de la evolución de los sistemas vivos (p.e. un sistema de 'vida artificial')? También se puede ver como un intento de elucidar la estructura lógica (en un sentido general) de evolución biológica. Sin embargo, win una definición adecuada de la vida, la parte experimental del trabajo se concentra en aspectos más específicos, y primariamente en el tema de evolución abierta-cerrada. Se introduce un sistema evolutivo artificial denominado Cosmos, que proporciona un sistema operativo virtual capaz de simular el procesamiento y evolución paralelos de una población de varios miles de programas informáticos auto-reproducibles. [...]

Dedica los primeros capítulos a introducción y discusión sobre el marco; así, dedica el segundo capítulo a 'Evolución y vida' y el tercero a 'Vida Artificial'. En la primera parte de este último, presenta el concepto de vida artificial, con matices y diferentes enfoques. Distingue entre 'vida artificial débil' frente a 'vida artificial fuerte'.

Abstract: "This work addresses the question: What are the basic design considerations for creating a synthetic model of the evolution of living systems (i.e. an `artificial life' system)? It can also be viewed as an attempt to elucidate the logical structure (in a very general sense) of biological evolution. However, with no adequate definition of life, the experimental portion of the work concentrates on more specific issues, and primarily on the issue of open-ended evolution. An artificial evolutionary system called Cosmos, which provides a virtual operating system capable of simulating the parallel processing and evolution of a population of several thousand self-reproducing computer programs, is introduced. Cosmos is related to Ray's established Tierra system [Ray 91], but there are a number of significant differences. A wide variety of experiments with Cosmos, which were designed to investigate its evolutionary dynamics, are reported. An analysis of the results is presented, with particular attention given to the role of contingency in determining the outcome of the runs. The results of this work, and consideration of the existing literature on artificial evolutionary systems, leads to the conclusion that artificial life models such as this are lacking on a number of theoretical and methodological grounds. It is emphasised that explicit theoretical considerations should guide the design of such models, if they are to be of scientific value. An analysis of various issues relating to self-reproduction, especially in the context of evolution, is presented, including some extensions to von Neumann's analysis of self-reproduction [von Neumann 66]. This suggests ways in which the evolutionary potential of such models might be improved. In particular, a shift of focus is recommended towards a more careful consideration of the phenotypic capabilities of the reproducing individuals. Phenotypic capabilities fundamentally involve interactions with the environment (both abiotic and biotic), and it is further argued that the theoretical grounding upon which these models should be based must include consideration of the kind of environments and the kind of interactions required for open-ended evolution. A number of useful future research directions are identified. Finally, the relevance of such work to the original goal of modelling the evolution of living systems (as opposed to the more general goal of modelling open-ended evolution) is discussed. It is suggested that the study of open-ended evolution can lead us to a better understanding of the essential properties of life, but only if the questions being asked in these studies are phrased appropriately."

Contents

• Contents
• List of Figures
• List of Tables
• Introduction
  • The Big Picture
  • Organisation of the Thesis
  • Major Contributions
  • Typographical Conventions
• Evolution and Life
  • Two Views of Life
  • The Origin of Life
  • The Pattern of Life
  • Playing the Game
  • Definition of Terms
  • Summary
• Artificial Life
  • What is Artificial Life?
    • Weak Artificial Life versus Strong Artificial Life
    • Is Artificial Life Possible?
    • Relation to Theoretical Biology
  • Previous Work
    • Self-Reproduction
    • Open-Ended Evolution
    • Self-Organisation and Origin of Life Models
  • Methodology and Design Issues for Artificial Life Platforms
• Design Details of the Cosmos Platform
  • Cosmos Design Philosophy
  • Preliminary Issues
  • The Structure of an Individual Cell
  • The Programming Language and Representation
  • The Environment
  • Actions and Interactions
    
  • The Top-Level Algorithm
  • Global Parameters
  • Input and Output Files
  • Major Differences between Cosmos and Tierra
  • Summary
• Cosmos Experiments 1:
  Detailed Analysis of a Standard Run
  • Analysis and Visualisation Techniques
  • Detailed Analysis of a Standard Run
• Cosmos Experiments 2: Exploring the Parameter Space
  • The Role of Chance6.2
  • Re-running the Standard Model
    
  • Mutations and Flaws
  • The CPU-time Distribution Scheme
    
  • Energy
  • Reading Neighbouring Code
  • Inoculation with Sexual Ancestors
  • Summary and Discussion
• Reappraisal of the Approach
  • Problems with Tierra-like Models
  • Self-Reproduction and Evolution Revisited
  • Improving the Approach
• Summary
• Cosmos System Details
  • Global Parameters
  • The REPLiCa Instruction Set
  • Predefined Ancestor Programs
  • Running Cosmos
  • Format of Input and Output Files
  • Implementation Details
• Details of the Reported Cosmos Runs
  • Default Values for Minor Parameters in Cosmos
  • The Standard Ancestor Program, 348AAAA
  • The Sexual Ancestor Program, 1314AAAA
  • Genetic Code
  • RNG Seeds for Runs in Chapter 6
• Bibliography