The concept of autopoiesis [3, 9] occupies a distinctive position in the entire field of biology as one of the very few substantive attempts to give an integrated characterisation of the nature of living systems which is clearly separate from a mere listing of arbitrary ``properties'' (such as metabolism, growth, reproduction etc.). The concept was originated some twenty-five years ago, by Humberto Maturana and Francisco Varela . Its influence since then has been diverse and sustained--see, for example, [13, 7].<Note 1>
The first widely distributed, and thus seminal, description of the concept of autopoiesis was that of , which was illustrated with a computer model of a ``minimal'' example. Experimental data from this model showed both the spontaneous formation and ongoing repair of an autopoietic system embedded in a two dimensional, discrete space. This was accompanied by a qualitative description of the artificial chemistry realised by the model, and a more detailed algorithmic account of the simulation program.
This computer model has been extremely influential in providing a relatively simple, graphic, exemplar of the concept of autopoiesis. It demonstrated that the idea of autopoietic organisation, although subtle and abstract, could be instantiated in a relatively simple, and concrete, system.
However: a recent reappraisal of the original presentation of this computer model has revealed significant flaws--flaws which, if they were left uncorrected, might tend to undermine its role as a concrete example of autopoiesis.
A number of technical difficulties with even interpreting the original algorithm, and apparent discrepancies between the algorithm and the experimental data, have been discussed in a previously published working paper . That paper also incorporates, as an appendix, the FORTRAN-IV code of a version of the original program used by Varela et al. Careful study of this code has now allowed the identification of an additional interaction, present in the code, but omitted from all published descriptions of the model.
In this paper we present experimental results from a completely new implementation of the qualitative chemistry described by Varela et al. which suggests that this additional interaction is, indeed, critical to the realisation of the autopoietic phenomena; and that, conversely, provided this additional interaction is included, the autopoietic phenomena are not dependent on any particular details of the original program or algorithm, but may be expected in any system sharing the same qualitative chemistry.
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Timestamp: Tue Apr 22 22:10:03 GMT 1997