ABSTRACT
The Darwinian synthesis focuses on speciation as the leading edge of evolution. But species are poor candidates for well-defined biological identity because they are always susceptible to giving rise to something new. Physicalist evolutionary developmental biology presents an alternative scenario in which broad differences between organismal types were ontologically and temporally prior to subtypes and species-level variants. The cell masses that first developed into the metazoans, or animals, for example, arose from unicellular antecedents by a set of molecular innovations that constituted the embryos of these organisms as an unprecedented form of matter – liquid and liquid crystalline tissues – and thus a natural kind. This novel material embodied a set of morphogenetic processes and motifs that laid the basis for subsequent animal evolution. With the addition of other molecular functionalities, organisms with simple “basal” metazoan body plans (exemplified in present-day sponges and placozoans) engendered more complex diploblasts (cnidarians, ctenophores) and bilaterian triploblasts (arthropods, chordates, molluscs, and so forth). Self-organising patterning processes arising within these integrated communities of cells produced segments, appendages, patterned skeletons, and organs. Bioelectrical scaffolding effects and the standardising influences of development from an egg transformed phylotypic forms into canalised, integrated individuals that exist in the biosphere as “natural purposes,” causes and effects of themselves.
