ABSTRACT
Brain expansion is accompanied by morphological, quantitative alterations within and between neural components. Comparative cytoarchitectonic studies of human, ape, and other primates reveal shifts in size of cortical layers, neuron density distribution, neuron to glial cell ratios, dendritic growth patterns, and subcortical nuclei volume and composition. These phenotypic observations are based on postnatal, mostly adult, tissue. A major hurdle to studying brain expansion in primates (especially humans and apes) is the scarcity of specimens representing fetal neocortical neurogenesis, when differences in brain size and organization first appear. Recent advances in cellular reprogramming technology have allowed for the recapitulation of early aspects of primate brain development in vitro and opened the possibility for direct comparisons of human and non-human primate brain tissues in two- or three-dimensional settings. These tools can reveal cellular processes and molecular pathways involved in neurodevelopment and tissue organization during primate brain expansion. This chapter examines critical aspects of brain reorganization in hominoids and reviews the use of induced pluripotent stem cell (iPSC) novel technology as a tool to study neurodevelopmental mechanisms present in primate brain expansion that have implications for hominoid evolution.
