The fourth dimension of tool use: temporally enduring artefacts aid primates learning to use tools

Abstract

All investigated cases of habitual tool use in wild chimpanzees and capuchin monkeys include youngsters encountering durable artefacts, most often in a supportive social context. We propose that enduring artefacts associated with tool use, such as previously used tools, partly processed food items and residual material from previous activity, aid non-human primates to learn to use tools, and to develop expertise in their use, thus contributing to traditional technologies in non-humans. Therefore, social contributions to tool use can be considered as situated in the three dimensions of Euclidean space, and in the fourth dimension of time. This notion expands the contribution of social context to learning a skill beyond the immediate presence of a model nearby. We provide examples supporting this hypothesis from wild bearded capuchin monkeys and chimpanzees, and suggest avenues for future research.

Keywords: Pan troglodytes; Sapajus libidinosus; artefact; expertise; niche construction; tools.

Figure 1.

(a) Rate per 10 min for all actions with a nut, (b) all direct percussion of an object on a substrate and (c) all percussion of a nut with a stone by young capuchin monkeys while near anvil or away from an anvil, when no other group members were cracking or when one or more other group members were cracking. Panels (a,b) present data from 11 monkeys; (c) presents data from the eight older monkeys, as the youngest three monkeys never struck a nut with a stone. The median is represented by the dark bar, the interquartile range by the shaded box, and the maximum and minimum values by the whisker lines. Outliers are indicated by stars.

Figure 2.

Sources of tools used by wild chimpanzees at Bossou, Guinea, as a function of the user's age (adult: over 10 years, weaned young: 5–10 years, unweaned young: 0–5 years) and the objects' previous history. ‘New tool’ refers to the use or manufacture of a tool not previously used by another individual; ‘tool re-use’ means that the individual is re-using an object previously used/made by another. The three panels correspond to three different forms of tool use: (a) Nut-cracking, (b) ant-dipping and (c) pestle-pounding. Only individuals that have been observed to perform the respective tool-use behaviours successfully are included in each dataset. Error bars are standard errors of the mean.