The common ancestor of all jawed vertebrates on Earth resembled a shark, according to a new analysis of the braincase of a 290-million-year-old fossil fish that has long puzzled paleontologists. Research on Acanthodes bronni, a Paleozoic fish, sheds light on the evolution of the earliest jawed vertebrates and offers a glimpse of the last common ancestor before the split between the earliest sharks and the first bony fishes — the lineage that would eventually include human beings.