Informal Seminar - Daniel Rokhsar

Abstract: Animals arose more than six hundred million years ago, and by the end of the Cambrian had diversified into today's phylum-level forms. This early history is obscured by the fact that the first animals were soft-bodied and left only enigmatic fossils. Here we take a comparative genomic approach to inferring the early evolutionary history of early animals and the subsequent events that gave rise to vertebrates. We show that animal chromosomes are generally stable over hundreds of millions of years (with notable exceptions), and exhibit characteristic modes of evolutionary change. Some gene linkages extend even further back in time, allowing early gene linkages to be polarized. We use these deeply conserved aspects of genome organization to (1) show that ctenophores rather than sponges are the earliest branching lineage of living animals, with implications for the early evolution of nervous systems, and (2) decipher the early history of Paleozoic polyploidy and interspecific promiscuity in our own vertebrate lineage.