Object relations and the origin of tools.
D000818:Animals; D000836:Animals, Zoo; D000883:Anthropology; D001288:Attention; D001522:Behavior, Animal; D005075:Biological Evolution; D003210:Concept Formation; D005106:Exploratory Behavior; D006801:Humans; D007100:Imitative Behavior; D007323:Instinct; D007360:Intelligence; D007858:Learning; D009769:Object Attachment; D002679:Pan troglodytes; D011574:Psychoanalytic Theory