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Self-Replicating Worms That Increase Structural Complexity
through Gene Transmission

Last modified on March 25, 2007
Copyright (C) 2000-2007 by Hiroki Sayama
Binghamton University, State University of New York

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This self-replicating cellular automata (CA) model was presented at Artificial Life VII: The Seventh International Conference on Artificial Life (August 1-6, 2000, Portland, Oregon) [1] as a latest effort toward the realization of an artificial evolutionary system on CA where structural complexity of self-replicators can increase in some cases. I utilize the idea of 'shape encoding' proposed by Morita and Imai [2, 3] and make the state-transition rules of the model allow organisms to transmit genetic information to others when colliding against each other. Simulations with random initial configuration demonstrate that it is possible that the average length of organisms and the average frequency of branching per organism both increase, with decreasing self-replication fidelity, and saturate at some constant level. The saturation is caused by the fixation of place and shape of organisms onto particular sites, which comes from the more significant assumption made in CA universe: "space equals material". This result implies that, in order to create complexity-increasing evolutionary systems using artificial media, it is necessary to develop a new framework of modeling, such as kinematic models of self-replication/evolution, in which material is separated from space and has definite limitation in quantity; i.e. spatial pressure is low enough to allow complex structures / strategies to survive.
Slides for presentation at the ALIFE VII (pdf, 870048 bytes)
[1] Hiroki Sayama: Self-replicating worms that increase structural complexity through gene transmission, Artificial Life VII: Proceedings of the Seventh International Conference on Artificial Life, M. A. Bedau, J. S. McCaskill, N. H. Packard and S. Rasmussen, eds., Portland, Oregon, pp.21-30, 2000, MIT Press. pdf (628671 bytes) ps.gz (812460 bytes)
[2] Kenichi Morita and Katsunobu Imai: Self-reproduction in a reversible cellular space, Theoretical Computer Science, vol.168, pp.337-366, 1996.
[3] Kenichi Morita and Katsunobu Imai: A simple self-reproducing cellular automaton with shape-encoding mechanism, Artificial Life V: Proceedings of the Fifth International Workshop on the Simulation and Synthesis of Living Systems, C. G. Langton and K. Shimohara, eds., pp.489-496, 1997, MIT Press.


Java applet

Simulator applet ver. 1.0 and ver. 1.1 (for small screen, which I have developed for my presentation at the ALIFE VII) are now available. Please consult the operation instruction before using them. A monitor of 1024x768 or higher resolution is recommended for ver. 1.0. They were tested on Microsoft IE 4.5 (Macintosh Edition) and Netscape Communicator 4.7 (Windows Edition). Any suggestions or bug reports will be appreciated.
Source codes are also available: Ver. 1.0 / Ver. 1.1
Note: This applet is believed to work correctly, but no liability is assumed to me for its use or for any damage resulting from its use. You may not use either this applet or the results gained by using this applet for any commercial purposes. You may use, distribute or modify this applet without permission for academic purposes.


Related sites

NECSI Artificial Self-Replication and Evolution Research Project
Artificial Life VII
Knowledge Engineering Laboratory at Hiroshima University (Morita & Iwamoto Lab.)
Artificial Self-Replication Page by M. Sipper


Comments, questions and suggestions are welcome.
sayama @ binghamton.edu