Peter Saunders Institute of Science in Society and Department of Mathematics, King's College London
Invited lecture at the Conference Evolution and the Future, Belgrade 14-17 October 2009 (to appear in Proceedings)
The fully referenced and illustrated paper can be downloaded here
The neo-Darwinist theory of evolution is fundamentally about genes. Random mutations occur, those that produce advantageous phenotypic traits spread through the population, and that is how change occurs. Any trait of an organism is to be explained by giving an account of the advantage it gives, and, if possible by indicating a sequence of small changes by which it could have appeared. Development, the process that comes between the genome and the phenotype is largely ignored as irrelevant to the outcome. It is seen as the study of construction rather than of architecture and design. Even the field of study known as “evo-devo”, that purports to bring evolution theory and developmental biology together, is about genes and their regulation.
Organisms are, however, constructed by physical and chemical processes. Nature can only select from among the forms that can appear, and the forms that are most readily made by developmental processes are the ones that are the most likely to be selected, not because they are necessarily the best conceivable but because they are available for selection.
Many years ago, CH Waddington pointed out that developing organisms possess what he called chreods, homeorhesis and canalization. These shared properties largely explain why there are discrete species instead of continuous variation and why major changes in evolution are likely to occur rapidly rather than by the gradual accumulation of small ones. These properties do not have to be explained as products of natural selection. They are typical of complex dynamical systems, which organisms certainly are.
Article first published 18/11/09
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