Discussion papers

CPM-02-87 - 18 January 2002

Surviving on a sand-pile: an investigation as to the type of behaviour that evolves in the presence of crises

Bruce Edmonds

To be presented at: the Network on Evolvability in Biological and Software Systems Symposium on “Evolvability and Individuality”, St. Albans, Hertfordshire, UK.


A simulation of artificial creatures is used to investigate the kinds of behaviour that might evolve under different environmental conditions. In particular, whether one might expect to find that evolution has resulted in behaviours that seem “well honed” with respect to the niche. The hypothesis is that this will only occur when the environment is relatively stable, that when the environment is swept with unpredictable crises there will be a greater variety of genes and behaviours.

To investigate this a 3D artificial world with creatures evolving on a sand pile was created. The creatures move, eat, turn, mate and propagate depending upon tree-structured program genes which are interpreted in each situation to produce the behaviour. These genes are type-sensitively tree-crossed when mating occurs to make the genome of the offspring. The environment is tuneable so that different sizes and frequencies of unpredictable avalanches occur.

Initial results seem to support the hypothesis. If it is true then this has implications for evolutionary explanations of behaviours, since it may not be the particular behaviour that is important but the range of behaviours that is significant. This has implications for the designers of animats and robots.

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