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Unbounded evolutionary dynamics in a system of agents that actively process and transform their environment

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Abstract

Bedau et al.'s statistical classification system for long-term evolutionary dynamics provides a test for open-ended evolution. Making this test more rigorous, and passing it, are two of the most important open problems for research into systems of agents that actively process and transform their environment. This paper presents a detailed description of the application of this test to ‘Geb’, a system designed to verify and extend theories behind the generation of evolutionarily emergent systems. The result is that, according to these statistics, Geb exhibits unbounded evolutionary dynamics, making it the first autonomous artificial system to pass this test. However, having passed it, the most prudent course of action is to look for weaknesses in the test. The test is criticized, most significantly with regard to its normalization method for artificial systems. Furthermore, this paper presents a modified normalization method, based on component activity normalization, that overcomes these criticisms. The results of the revised test, when applied to Geb, indicate that this system does indeed exhibit open-ended evolution.

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Notes

  1. Maley [21] makes the claim that two of his models, ‘Urmodel 3’ and ‘Urmodel 4’, exhibit unbounded evolutionary dynamics. However, Urmodel 3 shows less new activity than its shadow (with no reason to think that it would become greater), Urmodel 4 shows a lower mean activity than its shadow and both are only examined during their initial growth stages, so these claims are not valid. To my knowledge, there have not yet been any other claims of unbounded evolutionary dynamics in an autonomous artificial system.

  2. I use the term “autonomous artificial system” to refer to an artificial system with no ongoing human intervention, so discounting systems such as the global economy, Internet traffic and evolutionary systems such as Pfeiffer [19] in which fitness is derived from user evaluation or interaction.

  3. Because positive new activity is required for classes 2 and 3, only systems that continue to generate new adaptations can be in these classes.

  4. Bedau has since altered his class numbering scheme.

  5. The Geb system is available without charge for research use. It can be download from \({\tt http://www.channon.net/alastair/\#Software}\).

  6. In order to avoid confusion, I only use the term neutral to refer to genetic variations that are phenotypically equivalent, and not in relation to shadow runs.

  7. The two sets of runs reported in this paper, each consisting of twenty runs with shadows, consumed a total of approximately three years of 1 GHz single-cpu time.

  8. Thanks to Mark Bedau for bringing this to my attention.

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Acknowledgments

Thanks to Mark Bedau for discussion and many helpful comments on this work. Thanks also to the anonymous reviewers for constructive criticism and helpful comments, and to Wolfgang Banzhaf for his help with the paper.

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  1. School of Computer Science, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK

    Alastair Channon

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Correspondence to Alastair Channon.

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Communicated by: W. Banzhaf

*Parts of this paper have been published in [10–12].

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Channon, A. Unbounded evolutionary dynamics in a system of agents that actively process and transform their environment. Genet Program Evolvable Mach 7, 253–281 (2006). https://doi.org/10.1007/s10710-006-9009-3

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