The 5-million-year-old great white swims in a body design already recognizable 300 million years ago. Around 300 million years ago, in the late Carboniferous to early Permian, the lineage that would give rise to all modern sharks was already swimming through Earth’s oceans. The fossil record points to early “stem selachians” — shark-like fish such as Cladoselache — as close approximations of the last common ancestor (LCA) of living sharks. While we cannot identify the exact species that sits at the branching point, fossils from this time capture the body plan that unites all sharks today: cartilaginous skeletons, replaceable teeth, paired fins, and streamlined forms built for predation.