Abstract

This chapter is concerned with the Cambrian explosion. It considers only one particular kind of explanation for the Cambrian radiation: that major innovations in animal body plan were produced from relatively few genetic changes of large phenotypic effect. It investigates the developmental genetic hypothesis of the origin and maintenance of body plans. This chapter suggests that the genetic architecture underlying body plans was not set during the Cambrian and has been immutable since. It shows that the link between body plan and phylum can become blurry when the minor phyla are considered.