Reconciling fossils, molecules and morphology in deep metazoan phylogeny
Philip Donoghue, University of Bristol, United Kingdom
In these more enlightened times it just seems ironic that there was once a heated controversy over the competing roles of morphology and molecules in elucidating evolutionary history. To be sure, it will never be possible to recover sequence data from the fossil organisms that populate the deep branches in metazoan phylogeny. But if our ultimate aim is to uncover organismal evolution – even through comparative genomics or comparative development – the fossil record remains integrally germane. Palaeontological data inform on the extent of evolutionary history, on the sequence and tempo of phenotypic character evolution and their geologic context also informs on the extrinsic environment and its evolution. However, there is nothing particularly unique about palaeontological data – it is much like any other kind of morphological data. Nevertheless, fossil data have been singularly influential in testing hypotheses – e.g. of development evolution, or the nature of ancestral organisms - because fossils have been all too frequently overlooked. Thankfully, there is a growing appreciation of the value of palaeontological data. At the same time, palaeontologists are increasingly recognizing that evolutionary history has not been written solely in stone, that it is possible to address core palaeontological problems using comparative developmental genetics to test hypotheses of homology, and using molecular phylogenetics to resolve phylogenetic problems. The development of mixed model phylogenetic methods are particularly promising in facilitating the comparative analysis of fossil and living taxa, drawing upon the power of both comparative morphological and molecular data, to better constrain understanding, even of Deep Metazoan Phylogeny.