A new discipline – Evolutionary Developmental Biology as Hall (1992) has called it – is in the process of being born. Its origins are scattered and heterogeneous: from von Baer and Haeckel, through D'Arcy Thompson, Garstang, de Beer and Waddington, to the many recent and current students of comparative developmental genetics and related topics whose work is examined herein. Its potential is enormous: essentially to build a bridge between the mechanisms of population genetics and evolutionary ecology on the one hand and the patterns of comparative anatomy and palaeontology on the other; and thereby to help unify evolutionary theory in general.

This book is intended to be a contribution to this new discipline. It has a focus, though not an exclusive one, on the origin of animal body plans. It probes the question of how the morphological ‘designs’ of the thirty-five or so animal phyla arose in a burst of creative evolutionary activity in the distant geological past. In particular, it asks the question: were the genetic, developmental and population-level processes involved the same as those occurring in present-day speciations? If not, then what was different about those key early evolutionary events? In attempting to answer these questions, the book ranges from molecules and cells through developing organisms and natural populations to cladograms and ancient fossils.

My own background is in evolutionary ecology and, to a lesser extent, in population genetics. However, to write this book I have had to divert time away from reading in my own field in order to cover all the areas mentioned above, and more besides.