A Full Specification for Open-Ended Evolution

Perhaps the most important point to be raised in the discussion of self-reproduction and evolution (Section 7.2) was that these processes operate within an environment rather than in isolation. The properties of this environment, and the ways in which evolving entities may interact with it (and with each other), fundamentally influence the evolutionary process.

Reflecting upon the significance of his work on evolution, and in particular on his demonstration of the possibility of machines which could build modified copies of themselves, von Neumann said ``It is clear that this is a step in the right direction, but it is also clear that it requires considerable additional analyses and elaborations to become really relevant'' [von Neumann 66] (p.131).

It has long been recognised that chief among these additional analyses and elaborations is the incorporation of the evolutionary process into a broader framework that also considers the properties of the environment. Holland has emphasised that the study of adaptation ``involves the study of both the adaptive systems and its environment. In general terms, it is a study of how systems can generate procedures enabling them to adjust efficiently to their environments'' [Holland 62] (p.299). Moreover, Conrad stresses that ``the characterization of the substrate is of such immense importance for the effectiveness of evolution'' [Conrad 88] (p.304).

Studies of evolution in vitro, such as Orgel's experiments with evolving RNA sequences using the viral enzyme Qβ replicase [Orgel 79], have also demonstrated the need for a better theoretical understanding of these issues. Maynard Smith explains:

``More or less independently of the starting point ... the end point is a rather small molecule, some 200 bases long, with a particular sequence and structure that enable it to be replicated particularly rapidly. In this simple and well-defined system, natural selection does not lead to continuing change, still less to anything that could be recognized as an increase in complexity: it leads to a stable and rather simple end point. This raises the following simple, and I think unanswered, question: What features must be present in a system if it is to lead to indefinitely continuing evolutionary change?'' [Maynard Smith 88] (p.221).

The question raised by Maynard Smith is exactly the one of interest in this section: What sort of system (in terms of individuals, interactions and environments) will give rise to an open-ended evolutionary process?