In spite of their close relatedness to humans, very little is known about orangutans' ontogenetic development. In particular, no previous study has focused on the emergence of social and emotional cognition in orangutans, i.e. of those abilities that allow an individual to interact and communicate with others, and to understand and predict others’ behaviours and mental states. To fill this unexpectedly large gap, the project will document the socio-cognitive development of a Sumatran orangutan infant born at Furuvik Zoo, by means of naturalistic observation and videorecording. The project is unique in its focus on social and emotional cognition in early orangutan ontogeny, and in its level of detail and method systematicity. In particular, the project will document the interactions of the infant with her progenitors and zoo keepers in order to track the onset and development of socio-communicative gaze behaviours, social communication, emotional cognition and social learning. Mechanisms mediating the emergence of these abilities, such as play, apprenticeship and parental teaching will be also closely investigated. The results will provide insight for outlining a natural history of socio-cognitive ontogenesis in Hominidae and will allow to evaluate current evolutionary theories claiming that socio-cognitive development lags in other ape species compared to humans, albeit such claims rely on insufficient empirical grounds.