Biology subjects

Proffitt, T.

Publications and source records attributed to Proffitt, T..

3 recordsLinked to original sources

bioRxiv2024

Material matters: raw material influences stone tool performance in capuchin monkeys

Identifying the conditions that facilitate tool use is a central focus in the field of human evolution and animal behavior. Particular interest lies in studying stone tool use by non-human primates, especially when stone hammers are used to open encased food sources. Percussive tool use is a rare and complex technological behavior which was also employed by our early hominin ancestors. It is widely theorized that environmental factors play a role in explaining the presence and absence of stone tool use across primate populations. Research to date has focused heavily on the quality and availability of tool-extractable foods, and how these compare to alternative food sources. There has been limited investigation into whether access to different types of raw tool material for hammerstones and anvils affects the efficiency of tool users when exploiting encased resources. Here, we quantitatively analyzed how percussive tools of different raw materials vary in their performance and durability. Wild capuchins (Sapajus libidinosus) in Brazil were provided with stones sourced globally from primate and hominin tool use sites. We measured the reliability with which monkeys could crack nuts when using different raw materials, the number of strikes required to open a nut or obtain a food reward, and how these metrics changed over time. We further reported variations in the durability of different raw materials which directly relates to how long a tool remains usable. Our results showed that differences in nut cracking reliability and efficiency were largely driven by the ability of the tool material to stabilize the nut. Furthermore, there was wide variation in tool durability, particularly for anvils. These results highlight the importance of considering raw materials among the ecological factors that can influence the selective benefits or costs of tool use behaviors. HIGHLIGHTSO_LIRaw material influences primate percussive stone tool durability and performance C_LIO_LIMaterials differ in their ability to stabilize food sources C_LIO_LIEfficiency of hammer strikes differed across materials C_LIO_LIDifferences in material performance did not depend on their capacity to from pits C_LIO_LIMaterial performance has consequences for food yield and energetic efficiency C_LI

animal behavior and cognition↗

bioRxiv2024

Social cues on stone tools outweigh raw material properties in wild primates

1.The ability to select appropriate tool material enabled early hominins access to new resources and environments. The underlying mechanisms driving tool selection effectively remain unknown. Observations of extant primates have demonstrated strong selectivity for specific tools, offering analogous insight into technological decision-making. However, whether tool selection is determined by individual experience alone or social information plays a role remained difficult to disentangle. Here, we used an experimental approach to investigate decision-making factors for tool selection in non-human primates. We provided naturalistic nut-cracking opportunities to wild capuchin monkeys, one of the most prolific extant tool users. We offered standardized stones varying in asocial (material properties) and social cues (evidence of previous use) to two populations, differing in their previous experience of natural materials. Our results show that both populations persistently selected tools based on their material properties when only asocial cues were provided. However, when provided with both asocial and social cues combined, they consistently selected previously used material regardless of material properties. These findings suggest that wild capuchin monkeys discriminate between raw material properties; however, prioritize social cues when present. Tool selection behaviors are therefore shaped by indirect social processes and highlight the importance of culturally transmitted information for skill acquisition in technological primates.

animal behavior and cognition↗

bioRxiv2024

Tool skill impacts the archaeological evidence across technological primates

The archaeological record offers insights into our evolutionary past by revealing ancient behaviour through stone and fossil remains. Percussive foraging is suggested to be particularly relevant for the emergence of tool-use in our lineage, yet early hominin percussive behaviours remain largely understudied compared to flaked technology. Stone tool-use of extant primates allows the simultaneous investigation of their artefacts and the associated behaviours. This is important for understanding the development of tool surface modification, and crucial for interpreting damage patterns in the archaeological record. Here, we compare the behaviour and the resulting material record across stone tool-using primates. We investigate the relationship of nut-cracking technique and stone tool modification across chimpanzees, capuchins, and long-tailed macaques by conducting standardized field experiments with comparable raw materials. We show that different techniques likely emerged in response to diverse nut hardness, leading to variation in foraging success across species. Our experiments further demonstrate a correlation between techniques and the intensity of visible percussive damage on the tools. Tools used with more precision and efficiency as demonstrated by macaques, show fewer use wear traces. This suggests that some percussive techniques may be less readily identified in the archaeological record.

animal behavior and cognition↗