Structuralism (biology)

Biological or process structuralism is a school of biological thought that objects to an exclusively Darwinian or adaptationist explanation of natural selection (in the Neodarwinian synthesis for example), arguing that other mechanisms also guide evolution, and sometimes implying that these supersede selection altogether.

Structuralists have proposed different mechanisms that might have guided the formation of body plans. Before Darwin, Étienne Geoffroy Saint-Hilaire argued that animals shared homologous parts, and that if one was enlarged, the others would be reduced in compensation. After Darwin, D'Arcy Thompson hinted at vitalism and offered geometric explanations in his classic 1917 book On Growth and Form. Adolf Seilacher suggested mechanical inflation for "pneu" structures in Ediacaran biota fossils such as Dickinsonia. Günter P. Wagner argued for developmental bias, structural constraints on embryonic development. Stuart Kauffman favoured self-organisation, the idea that complex structure emerges holistically and spontaneously from the dynamic interaction of all parts of an organism. Michael Denton argued for laws of form by which Platonic universals or "Types" are self-organised. Stephen J. Gould and Richard Lewontin proposed biological "spandrels", features created as a byproduct of the adaptation of nearby structures. G. B. Muller and S. A. Newman argued that the appearance in the fossil record of most of the current phyla in the Cambrian explosion was "pre-Mendelian" evolution caused by physical factors. Brian Goodwin, described by Wagner as part of "a fringe movement in evolutionary biology", denies that biological complexity can be reduced to natural selection, and argues that pattern formation is driven by morphogenetic fields.