Hominin-specific protein that promotes development and evolutionary expansion of the brain neocortex (PubMed:25721503, PubMed:27957544, PubMed:30484771, PubMed:32554627, PubMed:33938018). Able to promote amplification of basal progenitors in the subventricular zone, producing more neurons during fetal corticogenesis, thereby playing a key role in neocortex expansion (PubMed:25721503). Promotes the proliferation of basal progenitors by inhibiting the mitochondrial permeability transition pore (mPTP): delays the opening of the mPTP via interaction with ADP:ATP translocase, thereby increasing mitochondrial Ca(2+) concentration and inducing glutamine catabolism, which is required for basal progenitor proliferation (PubMed:31883789). Does not possess GTPase activator activity: the absence of GTPase activator activity is required to promote amplification of basal progenitors during neocortex development (PubMed:25721503, PubMed:27957544). Interacts with ADP:ATP translocase components SLC25A4/ANT1 and SLC25A5/ANT2. Specifically expressed in radial glia cells of cortical neural stem and progenitor cells (NPCs) during neocortex development. Preferentially expressed in apical and basal radial glia (PubMed:25721503). Not detected in cortical neurons and cortical plate (PubMed:25721503). When expressed in embryonic mouse neocortex, promotes basal progenitor generation and self-renewal, and can increase cortical plate area and induce gyrification (PubMed:25721503, PubMed:33938018). Mice exhibit increased neocortical size and upper-layer neuron numbers persisting into adulthood (PubMed:33938018). Moreover, mice display altered neurobehaviour, characterized by an increased memory flexibility and a reduced anxiety level (PubMed:33938018). When expressed in the developing neocortex of the gyrencephalic ferret, strongly increases proliferative basal radial glia, a progenitor cell type thought to be instrumental for neocortical expansion, resulting in extension of the neurogenic period and an increase in upper-layer neurons (PubMed:30484771). As consequence, the postnatal ferret neocortex displays increased neuron density in the upper cortical layers and expands in both the radial and tangential dimensions (PubMed:30484771). Expression in fetal neocortex of the common marmoset increases the numbers of upper-layer neurons, promoting enlargement of the neocortex and inducing its folding (PubMed:32554627). ARHGAP11B arose from partial duplication of ARHGAP11A on the human lineage after separation from the chimpanzee lineage, but before the divergence from Neandertals. Although it contains a Rho-GAP domains, does not have GTPase activator activity (PubMed:25721503, PubMed:27957544). The absence of GTPase activator activity is required to promote amplification of basal progenitors (PubMed:27957544). Restoring this activity abolishes ability to promote amplification of basal progenitors during neocortex development (PubMed:27957544).