Chaînes opératoire and resource-exploitation strategies in chimpanzee (Pan troglodytes) nut cracking

Citation: Carvalho, S., Cunha, E., Sousa, C., Matsuzawa, T. (2008) Chaînes opératoire and resource-exploitation strategies in chimpanzee (Pan troglodytes) nut cracking. Journal of Archaeological Science (RSS)
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Summary

Theoretical background:

Based on use-wear analysis of stone tools, some scholars argue that tools used by chimpanzees are similar to Oldowan tools; however, there is a morphological difference between chimpanzees’ stone hammer and Oldowan hammers. In order to further understand material culture of chimpanzees, the author focuses on the operational sequence used by wild chimpanzees in nut cracking with stone tools at the sites of Bossou and Diecké, which are located in southeastern Guinea in West Africa. By adopting the Chaîne opératoire conceptual framework and conducting an interdisciplinary approach between archaeology and primatology, the author seeks to provide a foundation for studying the technological evolution of early hominins.

Methods and Materials:

According to the concepts of Chaîne opératoire, the author records and compares the operational sequence used by chimpanzees from three places, experimental nut-cracking sessions in Bossou-Nimba, natural nut-cracking sites in Bossou area, and natural nut-cracking sites in Diecké Forest. For experimental sessions, 7 piles of nuts and 2 stone groups which were divided from 57 stones were placed in a 7*20m rectangular outdoor laboratory area. This placement were standardized and maintained by datum point and GPS. They filmed the activities of chimpanzees, and drawn the tool movement after every sessions in order to observe the operational sequence and spatial distribution. The record ended up with 29 sessions which are 18 hours. For the natural sites in Bossou, they conducted occasional record by video and photograph, and they identified tool function mainly depends on the relative position of stones and fresh traces. For the natural sites in Diecké, indirectly method such as refitting was conducted. The data was analyzed by statistical method, including parametric and nonparametric test, which depends on the nature of data. Chi-square test and t-test are the main methods in this paper.

Results:

Results point out several important finding. First, the comparison from three sites suggests that there is a regional diversity in stone tool technology and typology. The size of hammer and anvil from these sites are different, which might result from the distinct nature of raw materials and food resource in environment. It shows that the ability of technological adaptations of chimpanzees and tool selection based on their sizes and weights. Thus, he thinks the different size of tools can not be a feature for distinguishing hominin tools and chimpanzee tools. Moreover, the behavior of nut cracking indicates there is a series of steps, including raw material selection, tool construction, transport, function selection, utilization, reuse, and discard. These different actions performed repeatedly in order to achieve a preexisting goal. Sometimes the chimpanzees would skip some steps or extend them, which reflect their flexible choice and adaptation. Besides, new tool transport to sites where the raw material is abundant indicates the possible tool preferences and possession. For the spatial distribution, it shows that there are three types of resource exploitation strategy, which explains the optimization and management of resources may be influenced by social constrains.

Theoretical and Practical Relevance

Tool use is not only limited to humans. Some species will also use tool to achieve their goals, especially the primates which is relevant to early hominin species. As Haslam et al.(2009) said, the long-term perspective to the material record of primates is important for understanding hominin technology and behavior. Previous studies stress the typology of tools by chimpanzees; however, this paper focuses on the operational sequences of nut cracking and proposed several points which tackles some cognitive capacity of chimpanzees to solve problems. He also found that the spatial pattern of resource-exploitation strategy is closed to those from Oldowan, and size of tools can not be a feature for distinguishing hominin tools and chimpanzee’s tool.

The resource strategies and operational sequences of chimpanzees shed the light on the development in human and nonhuman primates. This paper does expend our knowledge of the material culture of primates, and provide a foundation to further study the technological evolution of early hominins. The author mentions there is different tool use pattern between male and female, and adult and juveniles. However, he did not describe how the relationship between gender (or age) and resource-exploitation strategy. If the author presents the results, we will have the better understanding of their social relationship.