Abstract

There have been rumblings for some time to the effect that the neo-darwinian synthesis of the early twentieth century is incomplete and due for a major revision. In the past decade, several authors have written books to articu- late this feeling and to begin the move towards a second synthesis. David Rollo, in his book Phenotypes (Kluwer, 1994), was among the first to attempt to bring the focus back to the problems posed by phenotypic evolution. In Phenotypic Evolution (Sinauer, 1998), Carl Schlichting and I framed the debate in terms of the integration of development, environ- ment and genetics by articulating the concept of “developmental reaction norms”.