Innovation, Novelty and the Origin of Multicellularity

Abstract

Against the background presented in the last four chapters of development as hierarchical, integrative and epigenetic at all levels from origins of germ layers, through body plans and embryos, to organs and tissues, I now turn to how change, especially morphological and functional change, occurs in evolution and whether our knowledge of development as hierarchical and interactive allows us to ‘explain’ the developmental basis of such evolutionary change. In the past, most evolutionary biologists have not seen epigenetics (or even a hierarchical approach) as a necessary component of the mechanisms of evolutionary change. That situation has changed dramatically.

‘A comprehensive theory of organismic form is needed that relates embryonic development to longer-term processes of evolution, with the rationale that phenotypic structural change must originate through changes in ontogeny, and the two processes must be linked.’ M. H. Wake, 1992b, p. 315