Chapter 3: Complex Adaptive Systems
3.1 INTRODUCTION The previous chapter introduced complex adaptive systems. As we saw, Darwinian evolution provides the paradigm case. Each fresh generation of organisms throws up a stream of genetic novelty, driving the biological system away from equilibrium. Nevertheless, natural selection extinguishes the least fit; and from within these ‘far from equilibrium’ systems, order emerges. This chapter explores these various forms of self-organisation, by reference to modern understanding of evolutionary mechanisms. As we shall see, depending on the values of their parameters, the behaviour of such systems can be seen as falling into the three zones – the orderly, the complex and the chaotic – that we have already encountered. In subsequent chapters we examine how far this provides us with a model of potentially wider applicability, including to human societies. 3.2 ADAPTIVE WALKS ON FITNESS LANDSCAPES 3.2.1 Genetic Novelties and Adaptive Walks The genetic make-up of an organism (its ‘genotype’) consists of ordered strings of genes which carry information in the form of DNA. These strings can mutate or recombine to produce genetic novelties in the offspring. Each gene can be represented as a dimension of genotypic space. The gene in question can then take a variety of values or ‘alleles’. We can then model the genotype as searching for novelty by varying one gene at a time (‘point mutation’), switching it to one of the other permitted values (for purposes of modelling, it is often assumed that there are just two possible values). This search process thus involves movement to an...
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