Anthropoid augmentations

Abstract

Abstract Long after the Eocene expansions, the cortex enlarged again during the Miocene, independently in three anthropoid lineages: platyrrhines, cercopithecoids, and hominoids. These changes didn’t occur because of complex social systems, frugivory, diurnal foraging, or predation threats per se. All these driving forces existed before the cortex enlarged. Instead, changes in and interactions among such factors drove cortical enlargement. In platyrrhines and cercopithecoids, cortical expansion occurred during the middle-to-late Miocene as global cooling stressed their forest habitats and led to resource volatility. In hominoids, cortical expansion occurred during the early Miocene, a time of stable climate but also of new, more effective predators. In all three anthropoid groups, individuals incurred a risk of predation during long-range foraging journeys in daylight. Accordingly, improvements in foraging choices, guided by new representations in anthropoid-specific cortical areas, provided a survival advantage by decreasing the frequency of unproductive choices.