The human brain matures more slowly than the brains of nonhuman primates. A key question is to what extent the timing of neuronal development is determined by the neurons themselves rather than by their setting within the developing brain. Schörnig et al. overexpressed the neurogenic transcription factor neurogenin 2 (NGN2) to convert chimpanzee, bonobo, and human pluripotent stem cells (PSCs) into neurons. Functional and transcriptional analyses tracked the development of these cells into excitatory neurons. The authors found that as expression of stem cell markers declined, neurites developed and the cells became synaptically networked. Subsequently, cortical and sensory neurons differentiated. The ape neurons got off to a quicker start than human neurons in terms of both morphology and spontaneous activity. Delays in morphological and functional activity may support the development of greater complexity in the human brain.

eLife 10, e59323 (2021).