Reappraisal of the Approach 7.1 Problems with Tierra-like Models

\There is nothing wrong with a good illusion as long as one does not claim it is reality." Howard Pattee ((Pattee 88] p.74) In the previous two chapters, the behaviour of Cosmos has been analysed in considerable detail. However, as suggested in Section 6.8, it is still unclear exactly what the scientiic value of these results is, in terms of what they can tell us about biological evolution, or about a more universal view of biology. It has been hard to escape the nagging feeling that many of the more interesting results we have seen have been dependent on rather speciic features of the system's design. On top of this, even though considerable time and eeort has been spent in analysing the system, we have only really scratched the surface of exploring the parameter space. Over the course of this work, I have come to see a number of problems with the general approach that has been taken, if it is to be used as a scientiic framework. In this chapter, I will discuss these problems and related issues, and suggest, in some fairly general ways, how the approach might usefully be modiied and extended. In this section I discuss some of the major problems (or at least sources of concern) that I perceive with Cosmos and other Tierra-like models. These are summarised in the following list: 187