I read an evo-devo article recently that I found quite interesting.
It can be found here:
Dr. Stuart A. Newman, professor of cell biology and anatomy at New York Medical College has proposed a concept that could drastically alter the current theory of evolution. While evolution is commonly thought to have happened very gradually, by small steps, Newman has come upon an alternative model that may give some insight into early animal evolution. Animals are developed with specific 'morphological motifs.' Embryos develop with specific arrangements of discrete tissue types (with non-mixing layers) and at certain points form distinct segments. As embryos develop, they fold, elongate and form appendages. This theme is true of all animals.
What Newman proposes is that the origination of the structural motifs of animal form was predictable and relatively sudden, with abrupt morphological transformations favored during the early period of animal evolution. His model I based upon inferences about the genetics of the single-celled ancestors of the animals. The single celled organisms are believed to have contained genes of the developmental-genetic toolkit we have come back to so often in class. The products of these genes enabled the ancestral clusters to produce the characteristic motifs by harnessing the middle-scale physical effects, described by Newman as physical effects or governing constraints on how single cellular organisms may orient themselves together. In this way, the same basic structural motifs are present in all animals, and the same toolkit genes serve the same, or similar, functions.