The ontogeny of manual skill in wild chimpanzees: Evidence from feeding on the fruit of Saba florida

When chimpanzees eat Saba florida fruit, the necessary processing requires extraction from within an inedible matrix, involving considerable manual dexterity at several stages, and typically elicits strong manual laterality: all these features suggest that it is a complex task for chimpanzees. Focal observations were made on 14 mother-infant pairs. Although infants gained fruit pulp and fruit parts from the mother, and reduced the need for bimanual coordination by feeding on still-attached fruit, they nevertheless used more varied procedures than adults to extract pulp. In contrast, adults often detached and transported several fruits at once, and used bimanual methods to open fruits. By 2 years old, infants were able to process whole fruits, but it was not until 4 years that they gained mastery of the full adult technique. Many of these changes can be understood in terms of maturation of manual abilities, including precision gripping, bimanual role differentiation and digit role differentiation. Social influences are also present, including synchronous feeding, close attention to the mother, and food-soli citation and sharing. We argue that adaptations for optimization of nutrition have the incidental consequence of scaffolding the learning process for the infant.