Wear patterns on Thai macaque tools, with photos of the tools in use (Haslam et al. 2013)
A common question asked about primate archaeology is how we can recognise primate tools. One approach is to take techniques developed for human tools and apply them to other apes and monkeys. In a study published in PLOS ONE last year, we found that use-wear – the pattern of damage on a tool’s surface resulting from its use – could reliably distinguish between Thailand macaque stone tools commonly used to open oysters and those used for other pounding tasks (Haslam et al. 2013). This research focused on the monkeys of Piak Nam Yai island, where stone tool use was first reported for Thai macaques following the 2004 Indian Ocean tsunami (Malaivijitnond et al. 2007).
The distinction between the two types of tool, described as ‘axe-hammer’ for a pick-like action typically used on oysters attached to a rock and ‘pound-hammer’ for a crushing action used to open objects placed on an anvil, was made early on in the study of these macaques (Gumert et al. 2009). For this study, we built on the earlier work by recording the different kinds of damage seen on the narrow points and broad faces of the tools, including whether the stone surface was crushed, pitted or fractured. Based on this pattern of damage, and using a sample of 60 tools which had been observed being used by the monkeys, we found that we could predict with over 90% reliability whether the tool had been used as an axe or pound hammer.
Apart from demonstrating that non-human primate tools can have use-wear that allows their differentiation from natural rocks in the environment, we hope to be able to use this finding to determine the kinds of activities that monkeys were performing in the past. Such predictions will be particularly useful for understanding tools recovered through archaeological excavations. With further development, we also plan to use these techniques to assess where, when and how macaque tool use spread around Thailand and neighbouring Burma.
Gumert M, Kluck M, and Malaivijitnond S. 2009. The physical characteristics and usage patterns of stone axe and pounding hammers used by long-tailed macaques in the Andaman Sea region of Thailand. American Journal of Primatology 71:594-608.
Haslam M, Gumert M, Biro D, Carvalho S, and Malaivijitnond S. 2013. Use-wear patterns on wild macaque stone tools reveal their behavioural history. PLOS ONE 8:72872.
Malaivijitnond S, Lekprayoon C, Tandavanittj N, Panha S, Cheewatham C, and Hamada Y. 2007. Stone-tool usage by Thai long-tailed macaques (Macaca fascicularis). American Journal of Primatology 69:227-233.