What Makes Us Human: Insights from the Evolution and Development of the Human Neocortex

"What makes us human?" is a central question of many research fields, notably anthropology. In this review, we focus on the development of the human neocortex, the part of the brain with a key role in cognition, to gain neurobiological insight toward answering this question. We first discuss cortical stem and progenitor cells and human-specific genes that affect their behavior. We thus aim to understand the molecular foundation of the expansion of the neocortex that occurred in the course of human evolution, as this expansion is generally thought to provide a basis for our unique cognitive abilities. We then review the emerging evidence pointing to differences in the development of the neocortex between present-day humans and Neanderthals, our closest relatives. Finally, we discuss human-specific genes that have been implicated in neuronal circuitry and offer a perspective for future studies addressing the question of what makes us human.