The human cerebral cortex has undergone rapid expansion and increased complexity during recent human lineage evolution. One striking feature of human corticogenesis is that it is highly protracted in time, from prenatal steps of neurogenesis to postnatal stages of neuronal wiring. This prolonged development is thought to contribute in an important fashion to increased cortical size but also enhanced circuit complexity and plasticity. Here we describe how in vitro and in vivo mouse – human chimeric brain experiments indicate that the species-specific temporal patterning of corticogenesis is surprisingly intrinsic to cortical progenitors and neurons. The underlying molecular mechanisms start to be uncovered, and include human-specific duplicated genes.