6.1 Alchemy

The Alchemy system was formulated by Walter Fontana and Leo Buss in an explicit attempt to examine the abstract problem of the emergence of biological organization (Fontana & Buss, 1994b,a).

An Alchemy universe or reactor embodies the abstract notion of molecular species, with internal, compositional, structure, and characteristic reactions between instances of these species. All reactions may be characterized as ``catalytic'' in the sense that the original reactants are preserved, unchanged. (This is possible because, in this abstract system, there is no ``conservation of matter'' so that reaction products can be created without any consumption of reactants.) There is no notion of ``space''--any reactant can potentially react with any other (this is also referred to as a ``well-stirred'' reactor).

Reactions are deliberately specified to occur under flow conditions--so that particular sets of molecular species can continue to inhabit the reactor on an ongoing basis only if they (collectively) regenerate themselves. Thus, by definition, only collectively autocatalytic sets can persist for extended periods in the Alchemy system.

Several different experimental arrangements and outcomes have been described. Briefly, if the possibility of individually autocatalytic molecules is allowed (the ``Level 0'' experiments) then reactors quickly become dominated either by one such species, or a co-operative network of such species. The latter connects these results with the Hypercycles of Eigen & Schuster (1979). Such networks are found to be unstable under perturbation and collapse to single autocatalytic species. If individual autocatalysis is dis-allowed (the ``Level 1'' experiments), then the spontaneous emergence and persistence of collectively autocatalytic reactions networks is reliably observed. This is consistent with Kauffman's analyses. Unlike the previous case, these networks tend to be rather stable under perturbation.

A further set of experiments (``Level 2'') considers the results of ``mixing together'', in one reactor, collectively autocatalytic sets that have first emerged in independent reactors. This is clearly related to my heuristic test for autopoiesis; but it differs critically in that the networks being brought together are different, rather than distinct instances of the same network. The results of these experiments are interesting in their own right, but do not relate to my concerns here. On the contrary, it seems clear that, because Alchemy deliberately eschews any notion of spatial structure in a reactor, there is no mechanism for spatial separation or containment. Therefore, even in the absence of any specific experiment, it seems that, if two instances of the same network are placed in a single reactor then they instantly lose all individuality, and become just a single instance.

Thus, although Fontana and Buss refer to Alchemy as being related to work on autopoiesis (as, indeed, it certainly is), I think that the collectively autocatalytic reaction networks exhibited should certainly not be considered as autopoietic; and given the deliberate elimination of spatial notions from the model, it seems that autopoietic organization cannot emerge, or be embedded, in such systems.

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Timestamp: 2003-03-28