I could dedicate an entire chapter to the intricacies and suitability of various structures or `substrates', but this is not necessary for our purpose. It suffices to say that at their level, each substrate is very important - if not critical - to what originates from neuronal structures, the neuron, the biological cell, proteins or genetic substrates such as DNA and RNA. Effects of low level impairments can cascade and expand over time [Elm05, p. 115]. Thus, for each of these structural levels there is an evolutionary pressure to improve internal organization and interactions with other levels. The internal organic medium is a basis for evolution and so is the external biotope. The structural levels extend up to the macroscopic ecology, providing a wide range of substrates spanning 12 orders of magnitude of scale at which evolution simultaneously does its work [Ray99].
Erik de Bruijn 2007-10-19