Analysis of wild macaque stone tools used to crack oil palm nuts

Abstract

The discovery of oil palm (Elaeis guineensis) nut-cracking by wild long-tailed macaques (Macaca fascicularis) is significant for the study of non-human primate and hominin percussive behaviour. Up until now, only West African chimpanzees (Pan troglodytes verus) and modern human populations were known to use stone hammers to crack open this particular hard-shelled palm nut. The addition of non-habituated, wild macaques increases our comparative dataset of primate lithic percussive behaviour focused on this one plant species. Here, we present an initial description of hammerstones used by macaques to crack oil palm nuts, recovered from active nut-cracking locations on Yao Noi Island, Ao Phang Nga National Park, Thailand. We combine a techno-typological approach with microscopic and macroscopic use-wear analysis of percussive damage to characterize the percussive signature of macaque palm oil nut-cracking tools. These artefacts are characterized by a high degree of battering and crushing on most surfaces, which is visible at both macro and microscopic levels. The degree and extent of this damage is a consequence of a dynamic interplay between a number of factors, including anvil morphology and macaque percussive techniques. Beyond the behavioural importance of these artefacts, macaque nut-cracking represents a new target for primate archaeological investigations, and opens new opportunities for comparisons between tool using primate species and with early hominin percussive behaviour, for which nut-cracking has been frequently inferred.

Unexpected hard‐object feeding in Western lowland gorillas

“…Primates such as bearded capuchin monkeys ( Sapajus libidinosus ), long tailed macaques ( Macaca fascicularis ), and chimpanzees ( Pan troglodytes ), rely on the mechanical advantage afforded to them through the use of hammer stones and anvils to extract nutritious endosperms from woody endocarps. This ingenuity permits access to highly nutritious food sources without the prerequisite morphological adaptations (Boesch & Boesch‐Achermann, ; Fragaszy, Izar, Visalberghi, Ottoni, & de Oliveira, ; Proffitt et al, ).…”

Auditory representation of learned sound sequences in motor regions of the macaque brain

“…In contrast to their limitations in vocal control, macaques possess highly developed abilities for fine motor control of their hands and arms, which are instrumental for tool use (48,49). These skills (and the ability to acquire them by learning) suggest the existence of internal models coupling the somatosensory and motor systems for nimble use of the forelimbs.…”

The zooarchaeology and paleoecology of early hominin scavenging

“…An alternative viewpoint is that the origin of hominin stone tool manufacture and use was related to plant processing. Two lines of evidence to support this idea are (a) the observation that the use of stone pounding tools by chimpanzees, capuchins and macaques is associated with consuming nuts and hard‐shelled invertebrates rather than meat, and (b) the analysis of usewear on the edges of stone tools from Kanjera South, Kenya indicating the stone tools at this 2.0 Ma were most often used to process a variety of plant materials (wood, grit‐covered plant tissues interpreted as underground storage organs [USOs], and stems of grass or sedges) in addition to meat …”