Evolution without natural selection: further implications of the daisyworld parable.

Daisyworld is a model dynamical system in which very simple mechanisms interact to produce complex behaviour. It was devised to show how regulation can arise without natural selection. Here we investigate the model in greater detail. We analyse the possible steady states and study the response of the system under different conditions, we consider the implications of the hysteresis which is found in this and many other non-linear systems, and we compare the properties of the model with those of systems that evolved solely by natural selection. Natural selection inherently concentrates on local optimization and immediate advantage rather than on robustness and long-term benefit. This makes some features of organisms hard to explain within the synthetic theory. The model suggests that the solution may simply be that natural selection was not the crucial factor in their evolution. When a system that has previously responded to challenge counter-intuitively or apparently not at all subsequently begins to react in the way one would expect, this should be taken as a warning that it is a regulated system and that the regulation may be about to break down. If that happens, there is likely to be a catastrophic change as the system either collapses altogether or else moves rapidly to the state it would have been in without regulation. Recovery, if possible at all, is likely to be unexpectedly difficult.