Evo-Devo: the Merging of Evolutionary and Developmental Biology

Introduction In the beginning of the 20th century, developmental biology was at the forefront of biology, but then declined and had a renaissance towards its end. The key to this revival were the techniques of molecular biology, which proved the great equalizer for all branches of biology. The fusion of molecular, developmental and evolutionary biology proved very fertile, and led to the birth of a new discipline, Evo-Devo. I would like to present a personal account on how this synthesis took place. We will consider here three main points: 1) How are the mechanisms of self-regulation of cell differentiation observed in animal development explained at the molecular level? 2) How were conserved ancestral gene networks common to all animals – which pattern the Antero-Posterior (A-P) and Dorso-Ventral (D-V) axes – used to generate the immense variety of animal forms? 3) How has the use of a common tool-kit of genes present in the ancestral animal genome channeled the outcomes of evolution through natural selection? The main conclusion that emerges from these genomic, developmental and evolutionary studies is that all bilateral animals – which comprise 30 of the 34 extant phyla – arose through gene mutation, duplication or deletion of the genome of a complex common ancestor, the Urbilateria (Ur: primeval; Bilateria: animals having bilateral symmetry).