page_title: Structuralism (biology)
section_title: Seilacher's pneu structures
hierarchical_section_title: Structuralism (biology) / History / Seilacher's pneu structures
caption_attribution_description: English: Cropped and digitally remastered version of another file masquerading as DickinsoniaCostata*.png (Can't remember which number should replace the *!)
context_page_description: Biological or process structuralism, also known as formalism, is a school of biological thought that objects to an exclusively Darwinian or adaptationist explanation of natural selection such as is described in the 20th century's modern synthesis. It proposes instead that evolution is guided differently, basically by more or less physical forces which shape the development of an animal's body, and sometimes implies that these forces 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.
context_section_description: Like Thompson, the palaeontologist Adolf Seilacher emphasised fabricational constraints on form. He interpreted fossils such as Dickinsonia in the Ediacaran biota as "pneu" structures determined by mechanical inflation like a quilted air mattress, rather than having been driven by natural selection.
caption: Dickinsonia fossil described as a "pneu" structure with chambers inflated like a quilted air mattress. In Adolf Seilacher's structuralist view, the structure is determined mechanically by the need to distribute the tension across the surface, rather than having been guided by natural selection.
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