ROBERT, Jason S.; Dalhousie University: Homeosis and Hopeless Monsters

Beginning with William Bateson’s (1894) coining of the term ‘homeosis’, I trace significant events in the history of this concept throughout the twentieth century. Key episodes include Goldschmidt’s account of hopeful monsters (1940), early and contemporary developmental work on homeotic genes, and recent attempts to explain the material basis of evolution (in both plants and animals) in terms of homeosis. In the latter regard, homeosis has almost always been associated with saltationism; a recent exemplar of this perspective is Jeffrey Schwartz’s (1999) work on changes in the timing of homeotic gene expression as the basis for the generation of new animal species. I then discuss some skeptical considerations about the roles of homeosis and saltation in animal evolution (particularly those of Akam 1998 and Budd 1999), but leave open the possibility that evolutionary change need not be gradual. To this end, I explore an hypothesis offered by Bateman and DiMichele (1994) to explain ‘saltational evolution’ in vascular plants – even though their results may not be generalizable beyond the plant kingdom. // Cited References: Akam M. (1998). Hox genes, homeosis and the evolution of segment identity: no need for hopeless monsters. Int J Dev Biol 42: 445-451. // Bateman RM and DiMichele WA. (1994). Saltational evolution of form in vascular plants: a neoGoldschmidtian synthesis. In Ingram DS and Hudson A (eds.), Shape and Form in Plants and Fungi. London: Academic Press. // Bateson W. (1894). Materials for the Study of Variation. London: Macmillan. // Budd G. (1999). Does evolution in body patterning drive morphological change // or vice versa? BioEssays 21: 326-332. // Goldschmidt R. (1940). The Material Basis of Evolution. New Haven: Yale University Press. // Schwartz JH. (1999). Sudden Origins: Fossils, Genes, and the Emergence of Species. New York: John Wiley and Sons.