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ISIS Lecture 18/11/09
What
Can Development Tell us about Evolution?
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
Abstract
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.
The
fully referenced and illustrated paper can be downloaded here
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