The complexity of human sociality, cognition and communication remains an evolutionary puzzle. Since we lack a fossilized record of behaviours and brains, we need to approach the question “what makes us human?” with a phylogenetic comparison. Chimpanzees, one of our closest living relatives, cooperate on both the dyadic and group level. They also show prolonged dependency through ontogeny and only slowly acquire complex skills required in ecological and social domains, including in tool use and vocal production. Coordinating a consortium project between Max Planck and CNRS institutes, I source wild ape brains after natural death. We demonstrate, that relevant brain pathways also mature through development. Chimpanzees offer a model system to examine social and ecological drivers that precipitated prolonged investment in brain growth and skill development through the first years of life.