In this article we compared four different great ape species in their intrinsic curiosity levels. This means we conducted the experiments with each ape alone, to control for the fact that ape curiosity to large extent is socially triggered. Our results suggest that curiosity followed a linear gradient across the four species in accordance with their sociality. We propose the social curiosity hypothesis to explain the observed pattern, reflecting those individuals in highly social species, like bonobos and chimpanzees, regularly are accompanied by conspecifics, and thereby accustomed to an abundance of social cues, leading to inhibited curiosity when alone, compared to more solitary orangutans. As such, our study implies that ape curiosity evolved interlinked with sociality.