6.2 $\alpha$-universes

The $\alpha$-universes are a category of abstract or model systems devised by John Holland over 20 years ago (Holland, 1976). They were loosely inspired by notions of basic biochemical organization, and were devised specifically to consider some issues in the spontaneous emergence of life. The systems are, broadly speaking, ``artificial chemistries'', with notions of atoms, molecules, and reactions between them (both catalysed and uncatalysed). There is an explicit notion of space, albeit only one-dimensional.

Holland discussed one particular $\alpha$-universe in detail. In this case, while (by design) no single molecular species would be autocatalytic, it is trivially the case that an infinite class of collectively autocatalytic networks can be instantiated. This fact can be interpreted--in retrospect--as a specific example of the results presented by Kauffman regarding the relatively weak conditions which are needed for such a phenomenon. Of course, Holland's results significantly predate Kauffman's more general results, and are expressed in a different vocabulary.

Holland's particular interest with this model system was to assess the expected emergence time of instances of such collectively autocatalytic networks. As it turns out, these results are of limited value. Although the reaction networks he cites are--abstractly--collectively autocatalytic, they are not in fact capable of sustaining themselves under the conditions envisaged by Holland (McMullin, 1992b). This is at least in part due to the specific dynamics of the system, including diffusion, and the occurrence of unanticipated ``side-reactions'' which were not allowed for in Holland's analysis. There is also a significant effect due to rapid depletion of the initial ``food set''.

It is possible (though, to my knowledge, no specific experiments have been carried out) that at least some of the $\alpha$-universe reaction networks might be successfully self-sustaining if the system were organized in the form of a flow reactor (i.e., with a continuing inflow of food set materials). However, regardless of that, this system actually does not provide any mechanism for spatial localization or containment which could be caused as a result of any reactions instantiated in the system. Therefore we can say that, even if it could be made to host a viable, self sustaining, reaction network, multiple instances of the same network would not be able to maintain their separation, but would inevitably merge together and become indistinguishable.

Therefore the $\alpha$-universes are not capable of exhibiting autopoietic agents, according to my heuristic test.

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Timestamp: 2003-03-28