Our cerebral cortex, a sheet of neurons, connections and circuits, comprises “ancient” regions such as the hippocampus and “new” areas such as the six-layered “neocortex,” found only in mammals and most prominently in humans. But when in evolution did the components of cerebral cortex arise and how did they evolve? Scientists at the Max Planck Institute for Brain Research in Frankfurt am Main studied gene expression in the neurons of the cortex of turtles and lizards, and found unexpected similarities and differences with the mammalian cortex. These results are a milestone towards reconstructing the evolution of the vertebrate brain.