Evolution of developmental decisions and morphogenesis: the view from two camps

Modern developmental biology largely ignores evolution and instead focuses on use of standard model organisms to reveal general mechanisms of development Evolutionary biologists more widely hold developmental biology to be of major consequence in providing potential insights into evolution. Evolutionary insights can enlighten our views of developmental mechanisms as much as developmental data offer clearer views of mechanisms which underlie evolutionary change. However, insights have been limited by the long-term disengagement of the two fields dating to the rise of experimental embryology in the 1890s. Molecular genetics now provides a powerful tool to probe both gene function and evolutionary relationships, and a greater connection has become possible. The expansion of experimental organisms beyond the standard model animals used in most studies of development allows us to ask deeper questions about the interaction of development and evolution. This paper presents an analysis of the complementary uses of the resulting data in the two fields as they grope for accommodation. Analysis of the radical changes in early develoment seen in closely related sea urchins with alternate modes of development illustrate the complementarity of developmental and evolutionary data. These studies show that what have been thought to be constrained mechanisms of axial determination, cell lineage patterning, and gastrulation in fact evolve readily and provide the means for the rapid evolution of development.