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portion of the available cellular space before the others, but also an environment in
which the wrecks of unsuccessful previous tries will be common. Sayama [14] has
faced this problem with a strategy based on the mechanism of structural dissolution:
in his model, the reproducing loops tend to melt into the quiescent environment once
they aren't able to reproduce.
Another common feature in the contributions mentioned in the previous paragraphs
is that the patterns are placed in the cellular space as an engineering product. Since
the question of the origin of life is crucial in understanding life itself [15], we think
that it is essential for the study of artificial reproduction (and for the insight that this
study could provide in the area of Artificial Life) to pose the question of the minimal
conditions for reproducing patterns to appear from a non-reproducing environment.
In this paper we are concerned with the construction of cellular patterns capable of
reproduction and robust against external perturbations (that is to say, that can
reasonably operate in the presence of nonquiescent environments). The purpose of our
design is mainly to explore the possibility of spontaneous emergence of reproducing
agents from a unstructured initial distribution of cell states.
Besides that, we have benefited from the fact that the models that have been
designed up to now offered different approaches to the problem of reproduction in
cellular spaces. In particular, we have compared the relative performance in pattern
emerging according to two different reproduction strategies: the genetic one, based
on the existence of a self-description of the pattern that is used as a blueprint in
reproduction, and the self-inspecting one, in which the reproducing patterns take
themselves as the model to guide the replication process.
2
Motivation and Approach
In [12] we proposed a model of a reproducing cellular pattern whose reproduction
strategy was based on self-inspection. Then we argued that self-inspection based
reproduction was a good choice for testing different properties that were relevant for
the role that reproduction plays in the biological world, and in particular, that it could
be adequate to study:
•
the spontaneous emergence of reproducers
•
the self-maintenance of reproducers in unfriendly environments
•
the possibility for reproducers to incorporate traits from random variations
necessary for evolutionary processes
All three goals share an essential precondition concerning the robustness of the
reproducing patterns in nonquiescent environments. On the one hand, the emergence
of reproducers cannot originate in a quiescent space, so it seems reasonable to expect
that the emerging structures will have to struggle in some kind of primeval soup of
cell-states, surrounded by simple components that are candidate to self-organize into
reproducing entities. So, if the reproducers were intended to work only in quiescent
environments they would never emerge, at least as a result of a continuous growing
process. In any case, should any pattern appear, it would by no means be able to
reproduce in a “dirty” environment. Thus, in order to be able to produce structure in a
non structured environment we need a degree of stability that minimizes the
interferences between the emerging patterns and the surrounding matter.
