Introduction to the Symposium: Developmental and Evolutionary Perspectives on Major Transformations in Body Organization

Abstract

Any comprehensive theory of organismal form must relate the short-term processes of embryonic development to the long-term processes of evolutionary change—in what Mayr (1982, 1994, 1997) termed and biology; see Mayr and Provine (1980) and Hall (1998) for overviews. Any integration of internal and external biology involves a synthesis, or at the very least a coming together, of developmental and evolutionary biology as Evolutionary Developmental Biology (Hall, 1998). Hence, a symposium on Developmental and Evolutionary Perspectives on Major Transformations in Body Organization, the selection of approaches and speakers, and the venue—the Society for Integrative and Comparative Biology. Although attempts to understand the processes and mechanisms underlying body organization have been made for millennia, two periods of particularly intense research activity stand out. The first, in the latter half of the 19th century, was characterized by the discovery that all animals are built from similar cells, tissues and organs; that these cells arise embryologically from the same germ layers; that embryos of very different organisms progress through surprisingly similar stages using similar developmental processes of cell division, migration, commitment, differentiation and morphogenesis (see Bowler, 1996; Gee, 1996 and Hall, 1998 for reviews). Still, embryos, larvae and adults of dif