Ape knapping then and now: limited spontaneous social learning of stone-tool production and use in non-human apes

Abstract

Ape knapping experiments complement human knapping experiments as a source of behavioural data to build hypotheses about the learning mechanisms underlying the acquisition of knapping skills in extinct hominins. In addition, ape knapping experiments provide information regarding the stone-related behaviours that could have preceded the systematic production and use of sharp stones in our lineage. In this chapter we review previous ape knapping experiments with a focus on those that tested apes' social learning abilities. Two studies, investigating one orangutan and one bonobo, concluded that both apes could socially learn sharp stone tool making and use from human demonstrations. These results were interpreted as evidence of the reliance of early hominins on social learning to acquire knapping skills. However, alternative explanations exist. We provide novel experimental data from two ape knapping experiments investigating the abilities of the two previously untested great ape species (chimpanzees and gorillas) to learn knapping from human demonstrations. Contrary to the previous studies, the chimpanzees and gorillas in our experiments did not acquire sharp stone tool making or use socially from human demonstrations. Thus, the observation of human demonstrations is insufficient for apes to acquire knapping abilities. This disparity in results between studies is unlikely to be explained by species differences in tool use proficiency but rather by the particular rearing background of the previously tested individuals. We discuss how our previous results on both the individual and social learning abilities of unenculturated, untrained orangutans compare to our new results on gorillas and chimpanzees. In addition, we comment on the general implications of ape knapping experiments for understanding the likely origin and maintenance of knapping skills in pre-modern hominins.