Stone Flakes Research Articles

Captive bonobos (Pan paniscus) apply precision grips when using flaked stone tools.

Current evidence suggests that flaked stone tool technologies did not emerge until ~3.3-2.6 million-years-ago (Ma). It is often hypothesized that early hominin (principally Ardipithecus and early Australopithecus) manual anatomy may have prevented an earlier emergence, as the forceful precision grips essential to flake tool-use may have been ineffectively performed by these species. Marzke, Marchant, McGrew, and Reece (2015) observed potentially forceful pad-to-side precision grips being recruited by wild chimpanzees (Pan troglodytes) during feeding behaviors, indicating that Pan-like manual anatomy, and therefore potentially early hominin anatomy, may be capable of effectively securing flake stone tools during their use. Here, we report on the grips recruited by four captive, human-trained, bonobos (Pan paniscus) during the use of stone and organic tools, including flake stone tools during cutting behaviors. It is revealed that pad-to-side precision grips are frequently recruited by these bonobos when securing stone flakes during cutting actions. In some instances, high forces could have been resisted and applied by the thumb and fingers. While our analyzes are preliminary and limited to captive individuals, and Pan is not suggested to secure flakes with the same efficacy as Homo or Australopithecus, it points to early hominins potentially being able to perform the precision grips required to use flake stone tools. In turn, the ability to gain tangible benefits from the effective use of flake tools (i.e., gain energetic returns from processing food resources) may have been - at least anatomically - possible in early Australopithecus and other pre-Early Stone Age hominin species. In turn, hominin manual anatomy may not be a leading restriction on the emergence of the earliest stone tool technologies.

Wild macaques challenge the origin of intentional tool production

Intentionally produced sharp-edged stone flakes and flaked pieces are our primary evidence for the emergence of technology in our lineage. This evidence is used to decipher the earliest hominin behavior, cognition, and subsistence strategies. Here, we report on the largest lithic assemblage associated with a primate foraging behavior undertaken by long-tailed macaques (Macaca fascicularis). This behavior results in a landscape-wide record of flaked stone material, almost indistinguishable from early hominin flaked pieces and flakes. It is now clear that the production of unintentional conchoidal sharp-edged flakes can result from tool-assisted foraging in nonhominin primates. Comparisons with Plio-Pleistocene lithic assemblages, dating from 3.3 to 1.56 million years ago, show that flakes produced by macaques fall within the technological range of artifacts made by early hominins. In the absence of behavioral observations, the assemblage produced by monkeys would likely be identified as anthropogenic in origin and interpreted as evidence of intentional tool production.

Identifying intentional flake production at the dawn of technology: A technological and 3D geometric morphometric study

The production of sharp-edged stone flakes is often viewed as a unique adaptation specific to the hominin lineage. The discovery of large stone cores and flakes dated to 3.3 Ma has shown that the earliest evidence of hominin stone flake production differs from the later Oldowan (dated to 2.6 Ma) record. Recent discoveries have shown that capuchin monkeys (Sapajus libidinosus) can unintentionally produce sharp-edged flake assemblages as a by-product of percussive behaviour. Capuchin monkeys are the only wild primate to intentionally strike two stones together (stone-on-stone percussion) to produce quartz powder. In doing so, they unintentionally produce high frequencies of sharp-edged flakes. It has been suggested that these possess the same technological attributes commonly used to describe intentional hominin stone flakes. Here we directly compare the basic morphometric descriptions, technological and 3D morphometric properties of unintentional capuchin flakes with experimentally produced flakes derived from two intentional flaking techniques employed during the Plio-Pleistocene, freehand and passive hammer knapping and a sample of Oldowan freehand flakes from Olduvai Gorge (Tanzania). Our results show that unintentional stone-on-stone flakes overlap in terms of their shape, size and technological attributes with those produced through intentional knapping techniques. We, however, identify attributes that may be critical for differentiating between intentional knapping techniques documented in the early archaeological record and unintentional flakes. Using these data we show that Oldowan flakes more closely resemble intentional freehand techniques.

Miniaturization and Abstraction in the Later Stone Age

This article offers some hypotheses to explain Later Stone Age lithic miniaturization: the systematic creation of small stone flakes on the finest-grained materials. Fundamentally, this phenomenon appears to represent the prioritization of stone tool sharpness over longevity, and a disposable mode of using stone tools. Ethnographic evidence from Australasia, the Andaman Islands, and Africa is used to suggest some specific functions for miniaturized lithics, as well as their relationship to other aspects of Later Stone Age material culture, including ochre crayons, shell beads, and notched bones. Miniaturized lithic functions are hypothesized to have a common basis in the cognitive capacity for abstraction: having ideas about ideas. The technological and social affordances of abstraction may have given later Homo sapiens significant adaptive advantages over other members of our genus.

Quantifying Edge Sharpness on Stone Flakes: Comparing Mechanical and Micro-Geometric Definitions Across Multiple Raw Materials from Olduvai Gorge (Tanzania)

In line with engineering research focusing on metal tools, techniques to record the attribute of ‘edge sharpness’ on stone tools can include both mechanical and micro-geometric approaches. Mechanically-defined sharpness techniques used in lithic studies are now well established and align with engineering research. The single micro-geometrically-defined technique—tip curvature—is novel relative to approaches used elsewhere, and has not explicitly been tested for its ability to describe the attribute of sharpness. Here, using experimental flakes produced on basalt, chert, and quartzite sourced at Olduvai Gorge (Tanzania), we investigate the relationship between tip curvature and the force and work required to initiate a cut. We do this using controlled cutting tests and analysis of high-resolution microCT scans. Results indicate cutting force and work to display significant dependent relationships with tip curvature, suggesting the latter to be an appropriate metric to record the sharpness of lithic tools. Differences in relationship strength were observed dependent on the measurement scales and edge distances used. Tip curvature is also demonstrated to distinguish between the sharpness of different raw materials. Our data also indicate the predictive relationship between tip curvature and cutting force/work to be one of the strongest yet identified between a stone tool morphological attribute and its cutting performance. Together, this study demonstrates tip curvature to be an appropriate attribute for describing the sharpness of a stone tool’s working edge in diverse raw material scenarios, and that it can be highly predictive of a stone tool’s functional performance.

The influence of cut material on the slicing efficiency effects of stone tool flake size, edge length, and gross edge curvature

Cutting actions were likely an important factor in the emergence and evolution of stone tools. In recent years, experiments have shown many factors can influence the efficiency of cutting behaviors, including tool form, tool material, and tool-user. Here, following other researchers, we test whether the material getting cut influences the efficiency effects of particular variables, namely flake size, cutting-edge length, and gross-edge curvature. Slicing six different materials, five participants used 300 stone flakes with quantitatively documented differences in flake size, cutting-edge length, and gross-edge curvature. The results of our Generalized Linear Mixed Models (GLMM) provide evidence that specimen size, edge length, and edge curvature have differential effects based on the material being cut.Our results support the hypothesis that the hominin need or desire to process particular materials potentially influenced the production and selection of stone tool forms over time and to different extents.

Stone tool backing and adhesion in hunting weaponry: First results of an experimental program

Stone tool backing repeatedly occurred on several continents throughout the Pleistocene and Holocene. Yet, any potential utilitarian advantages or disadvantages of backed stone tools relative to non-backed tools has been experimentally under-explored. Modern engineering experiments involving adhesion mechanics suggest an inverse relationship between surface area and the strength of a bond, especially on heterogeneous surfaces like stone. Some stone flakes, especially those with longer edges, may have been backed to make them easier to hold and safer to use. Further, Stone Age humans hafted both backed and un-backed tools for millennia in many parts of the world, suggesting effective hafting could occur with or without backing. Backing itself is a relatively simple technique providing toolmakers with an easy way to shape stone flakes. Some archaeologists have even hypothesized backed tool shaping was an end to communicate social information via stone symbols. This is the first pilot in a series of experiments testing a straightforward null and alternative hypothesis assessing the relationship between backing and adhesion and shaft damage with respect to projectile weaponry. Overall, our experimental results suggested two central conclusions with respect to backing. First, backing does not appear to improve adhesion but instead significantly worsens it. Second, laterally backed tools seem to increase the chances of shaft splitting relative to laterally hafted non-backed tools. Assuming for a moment that our results are supported by our future experimental research, our findings suggest that factors other than increased adhesion, such as intentional ‘failure,’ drift, or non-functional bias during social signaling or symbolic communication events, may have been responsible for the adoption and transmission of backed tools.

Free hand hitting of stone-like objects in wild gorillas

The earliest stone tool types, sharp flakes knapped from stone cores, are assumed to have played a crucial role in human cognitive evolution. Flaked stone tools have been observed to be accidentally produced when wild monkeys use handheld stones as tools. Holding a stone core in hand and hitting it with another in the absence of flaking, free hand hitting, has been considered a requirement for producing sharp stone flakes by hitting stone on stone, free hand percussion. We report on five observations of free hand hitting behavior in two wild western gorillas, using stone-like objects (pieces of termite mound). Gorillas are therefore the second non-human lineage primate showing free-hand hitting behavior in the wild, and ours is the first report for free hand hitting behavior in wild apes. This study helps to shed light on the morphofunctional and cognitive requirements for the emergence of stone tool production as it shows that a prerequisite for free hand percussion (namely, free hand hitting) is part of the spontaneous behavioral repertoire of one of humans’ closest relatives (gorillas). However, the ability to combine free hand hitting with the force, precision, and accuracy needed to facilitate conchoidal fracture in free hand percussion may still have been a critical watershed for hominin evolution.

Experimental assessment of plan‐view and profile‐view gross‐edge curvature on stone flake slicing efficiency

AbstractSeparating two or more aspects of an object via cutting was likely an important factor in the origin and evolution of flaked stone technology. In recent years experiments have demonstrated that several stone tool attributes can influence different kinds of cutting behaviour: slicing, cleaving, scraping, sawing, drilling, piercing and abrading. Here we experimentally assessed the role of stone flake plan‐ and profile‐view gross‐edge curvature in a controlled slicing task. We also assessed the role of edge length. A total of 21 participants, using 252 stone flakes with distinct gross‐edge curvatures and edge lengths, were asked to cut through a standardized substrate, and their efficiency in the task was measured over time. Flakes with longer edge lengths increased the efficiency of the cutting task, but increasing either plan‐ or profile‐view edge curvature decreased the efficiency of the cutting task. These results have implications for the emergence of particular tool forms or reduction sequences throughout the Pleistocene, and may in part explain why certain forms were favoured by Paleolithic people, leading to their convergent evolution or widespread transmission.

Physical Properties of Eco-Sustainable Form-Stable Phase Change Materials Included in Mortars Suitable for Buildings Located in Different Continental Regions.

Starting from two low-cost, low-environmental-impact polymers belonging to the Polyethylene Glycol (PEG) family, i.e., PEG 800 and PEG 1000, two form-stable phase change materials were produced. The two PEGs differ in molecular weight and, as a consequence, the melting and crystallization range of temperatures. The PCMs were obtained, including the PEG, in a liquid state, inside the pores of Lecce Stone flakes, obtained as waste pieces from its processing. A simple and inexpensive impregnation process was selected to produce the PCMs, thus adopting low-environmental-impact materials and cheap processes, and respecting circular economy principles. The two PCMs, the first composed of PEG 800, namely LS/PEG800, and the second composed of a 50/50%wt. mix of the different LS/PEGs, i.e., LS/PEG800_LS/PEG1000, were added as aggregates to four types of mortars, based on aerial and hydraulic lime, gypsum, and cement. The obtained mortars were characterized in their fresh state to assess their workability, and in a solid state after a proper cure to determine their characteristic Latent Heat Thermal Energy Storage (LHTES) properties and mechanical properties in both flexural and compressive modes, taking the mortars not containing any PCM as the reference. The results revealed that, with the proper selection of mortar formulations, it was possible to achieve suitable workability and adequate mechanical characteristics. The selection of a PEG with a low range of phase change temperatures, such as PEG 800, allows one to obtain mortars characterized by a melting/crystallization range that can be considered appropriate in applications characterized by cold climates. The production of a mixed PCM, composed of both PEGs, led to mortars displaying a large interval of melting/crystallization temperatures, which could be suitable in both warm and cold climates.

Physical Properties of an Eco-Sustainable, Form-Stable Phase Change Material Included in Aerial-Lime-Based Mortar Intended for Different Climates.

The aim of this experimental investigation was to produce a form-stable phase change material (PCM) able to reduce the need for nonrenewable energy resources required for the heating/cooling of buildings located in regions characterized by different climatic conditions. The innovative PCM must also be sustainable and must be produced according to the principles of the circular economy. To achieve such ambitious goals, a form-stable, sustainable PCM was produced through vacuum impregnation. The form-stable PCM was produced starting from a low-toxicity, low-flammability polyethylene glycol of medium molecular weight (PEG 800), which was included in porous stone granules obtained as waste products of the cutting/processing of local (Lecce) stone. The thermal properties and thermal stability of PEG 800 and of its PCM-composite were evaluated by employing differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). The appropriate parameters to perform the impregnation procedure were identified through rheological and calorimetric analyses. A simple leakage test was performed to assess if the PEG polymer can leak from the stone flakes. Finally, the new PCM was added as an aggregate in aerial-lime-based mortars, and the mortar’s properties were analyzed in fresh (workability) and hardened (flexural and compressive strength and thermal characteristics) states for potential applications, particularly in ancient buildings.

The mediating effect of platform width on the size and shape of stone flakes.

To understand the ways in which past stone knappers controlled the morphology of the flakes they produced, archaeologists have focused on examining the effects of striking platform attributes on flake size and shape. Among the variables commonly considered, platform width has routinely been noted to correlate with flake size and hence used to explain past knapping behaviors. Yet, the influence of platform width on flake variation remains equivocal due to the fact that the attribute is not under the direct control of the knapper. Instead, platform width tends to be treated as a by-product of other independent knapping parameters, such as platform depth. In this study, we hypothesize that platform width acts as an intermediary that intervenes the effect of other independent variables on flake attributes. By analyzing experimental flakes produced under both controlled and replicative settings, the results support the hypothesis that platform width mediates the effect of platform depth on flake width, such that flakes with relatively larger platform widths are generally wider but no longer. This finding provides a way to incorporate platform width into discussions of the interrelationships among knapping variables, and highlights the importance of platform width for investigating how past knappers controlled flake production through platform manipulation.

Use-polished stone flakes from Liang Bua, Indonesia: Implications for plant processing and fibrecraft in the Late Pleistocene

Edge-glossed flakes, usually recognised as stone tools with macroscopically visible polish from use, have been documented in parts of Southeast Asia from contexts spanning the past 12,000 years and possibly more than 30,000 years. It has been proposed that the edges of these flakes were polished by cutting, splitting or otherwise processing siliceous and fibrous plants for matting, basketry and bindings, and possibly by the reaping of cereals such as rice. Previous studies of use-wear on edge-glossed flakes in Southeast Asia have suggested several tool functions, including the cutting, splitting and scraping of plants with few or no phytoliths (e.g., Pandanaceae) and highly siliceous plants, with high phytolith content, such as Arecaceae palms (e.g., rattan) and Poaceae grasses (e.g., rice, bamboo and cattail reeds). Our study of the use-wear on 16 edge-glossed flakes from layers spanning the past 18,000 years at Liang Bua, a limestone cave on the Indonesian island of Flores, Indonesia, indicates processing of various plant taxa, including Poaceae grasses, Arecaceae palm and wood. The edge-glossed flakes from Liang Bua have features of micropolish that indicate they were probably linked with fibrecraft. Eleven of the 16 Liang Bua artefacts with edge-gloss are between about 18,580 and 11,750 years old, from artefact assemblages associated with modern humans; they currently represent the earliest evidence of these behaviours on Flores. No edge-glossed flakes have yet been identified in the 190,000–50,000-year-old artefact assemblages associated with Homo floresiensis.

Did the use of bone flakes precede the use of knapped stone flakes in hominin meat processing and could this be detectable archaeologically?

The means by which hominins invented lithic cutting technology is currently unknown. However, the origin of stone knapping is frequently associated with nut-cracking, whereupon hominins are assumed to have accidentally produced flakes and/or transferred a percussive motion to stone cobbles. Here, we consider whether bone flakes produced during marrow acquisition might have inadvertently produced the first ever cutting tools, and whether such a hypothesis is archaeologically testable. Bone and stone flakes were compared during an experimental butchery activity and an examination of resulting cut marks was undertaken. Use of bone flakes leaves visible cut marks, which are quantitatively and qualitatively distinct from those produced by stone flakes. Accordingly, hominins could have used the expediently manufactured bone flakes during butchery, possibly even utilizing bone flakes prior to the invention of stone flakes. Indeed, this scenario is more parsimonious compared with more commonly considered alternatives. Moreover, our results indicate this scenario is archaeologically testable.

Quantifying differences in hominin flaking technologies with 3D shape analysis

Genetic and climate-driven estimates of past population dynamics are increasingly influential in broader models of hominin migration and adaptation, yet the contribution of stone artifact variability remains more contentious. Scientists are increasingly recognizing the potential of unretouched stone flakes (‘flakes’) in exploring existing models of hominin behavioral evolution. This is because flakes (1) were produced by all stone tool manufacturing groups in the past, (2) are abundant from the inception of the archaeological record up into the ethnographic present, and (3) preserve under most conditions. The statistical tools of 3D geometric morphometrics capture detailed approximations of flake form that are challenging to document with conventional artifact analyses. We analyze a collection of 717 3D scans of experimentally produced flakes from 5 production strategies that were practiced by hominins through large parts of the Pleistocene and that scientists have drawn on also to make demographic arguments about past human behavior (n = 45 reduction sequences, n = 3 knappers naive toward the study objectives). First, as a proof of concept, we demonstrate that we can estimate the strategies used to produce these flakes at a high success rate even when flakes from early stages of core reduction are included. We frame the significance of this finding against archaeological classifications from several key Middle Paleolithic assemblages in France (n = 4 sites, n = 28 layers, n = 16,467 flakes). Second, we show that 3D geometric morphometrics captures subtle differences in these strategies that influence flake formation on a flake-by-flake basis and that reflect decisions made by knappers about platform selection, preparation, and core-surface management. We explore the broader potential of our model with a cross-validation approach, and we describe a means of assessing flake form on a continuum wherein variability among assemblages separated by large expanses of space and time can be meaningfully explored.

Kinetics of stone tool production among novice and expert tool makers.

As is the case among many complex motor tasks that require prolonged practice before achieving expertise, aspects of the biomechanics of knapping vary according to the relative experience/skill level of the practitioner. In archaeological experiments focused on the production of Plio-Pleistocene stone tools, these skill-mediated biomechanical differences have bearings on experimental design, the interpretation of results, and lithic assemblage analysis. A robust body of work exists on variation in kinematic patterns across skill levels but less is known about potential kinetic differences. The current study was undertaken to better understand kinetic patterns observed across skill levels during "Oldowan," freehand stone tool production. Manual pressure data were collected from 23 novice and 9 expert stone tool makers during the production of simple stone flakes using direct hard hammer percussion. Results show that expert tool makers experienced significantly lower cumulative pressure magnitudes and pressure-time integral magnitudes compared with novices. In expert knappers, digits I and II experienced similarly high pressures (both peak pressure and pressure-time integrals) and low variability in pressure relative to digits III-V. Novices, in contrast, tended to hold hammerstones such that pressure patterns were similar across digits II-V, and they showed low variability on digit I only. The similar and consistent emphasis of the thumb by both skill groups indicates the importance of this digit in stabilizing the hammerstone. The emphasis placed on digit II is exclusive to expert knappers, and so this digit may offer osteological signals diagnostic of habitual expert tool production.

Measurement of material volumes in a cylindrical silo using acoustic wave and resonance frequency analysis

This work presents an approach for measuring material volumes in a closed cylindrical silo by using acoustic waves and resonance frequency analysis of silo’s acoustic systems. With an assumption that the acoustical systems were linear and time-invariant, frequency responses of the systems were identified via measurement. A sine sweep was generated, amplified and fed to a loudspeaker inside the silo. Acoustic waves were picked up by a microphone and processed to yield the silo's frequency response. Resonance frequencies and wave mode numbers of standing waves in the frequency range below 900 Hz were analyzed and used for calculation of air-cavity lengths. With known silo's dimension, the material volume estimations were achieved. Sets of experiments for estimating volumes of sand, cement, water, rice grain, and stone flakes in a closed silo, were done. It was found that the approach could successfully estimate the volumes of sand, cement, and water with a satisfactory accuracy. Percent errors of the estimations were less than 3% from the actual volumes. However, the approach could not estimate the volume of rice grain and stone flakes, since their sound refractions were neither resulted in standing waves nor acoustical modes in the silo.

The dnỉ-Measure in Ancient Egyptian Tomb Construction Projects

When constructing the rock-cut tombs in the Theban necropolis, the ancient Egyptian builders kept track of the progress by recording the amount of rock that was excavated. This is clear from Eighteenth Dynasty ostraca from the tomb chapel of Senenmut, TT 71, which record stages of excavation and measure the production output in units of dnỉ. The current article reconfirms the observations of J. Černý on the dnỉ-unit and its usage as a measure exclusively for capacity, particularly in building projects involving excavation of rock. From this, the article outlines the implications for the understanding of other tomb construction terminology, in particular the ȝʿʿ, the šʿd and the dḳr. The consequence is to acknowledge that the tomb builders of Senenmut only recorded progress of excavation, and not different stages of decoration. In addition, the article suggests that baskets filled with stone flakes at Deir el-Bahri from the Middle Kingdom may represent a practical use of the dnỉ-unit.

What is ‘in situ’? A reply to Harmand et al. (2015)

The production of sharp-edged stone flakes is often viewed as a unique adaptation specific to the hominin lineage. The discovery of large stone cores and flakes dated to 3.3 Ma has shown that the earliest evidence of hominin stone flake production differs from the later Oldowan (dated to 2.6 Ma) record. Recent discoveries have shown that capuchin monkeys (Sapajus libidinosus) can unintentionally produce sharp-edged flake assemblages as a by-product of percussive behaviour. Capuchin monkeys are the only wild primate to intentionally strike two stones together (stone-on-stone percussion) to produce quartz powder. In doing so, they unintentionally produce high frequencies of sharp-edged flakes. It has been suggested that these possess the same technological attributes commonly used to describe intentional hominin stone flakes. Here we directly compare the basic morphometric descriptions, technological and 3D morphometric properties of unintentional capuchin flakes with experimentally produced flakes derived from two intentional flaking techniques employed during the Plio-Pleistocene, freehand and passive hammer knapping and a sample of Oldowan freehand flakes from Olduvai Gorge (Tanzania). Our results show that unintentional stone-on-stone flakes overlap in terms of their shape, size and technological attributes with those produced through intentional knapping techniques. We, however, identify attributes that may be critical for differentiating between intentional knapping techniques documented in the early archaeological record and unintentional flakes. Using these data we show that Oldowan flakes more closely resemble intentional freehand techniques.

Thermal curved-fragments: A method for identifying anthropogenic fire in the archaeological record

The archaeology of fire is a developing field. One challenge centers on equifinality: distinguishing the affects of wildfire versus anthropogenic fire. Especially where evidence for control of fire by humans in the early Pleistocene remains debated, there is little consensus regarding what constitutes clear evidence of human-control. Another concern is preservation bias, which reduces clearly identifiable archaeological signatures of fire. In this paper we argue that a peculiar lithic angular fragment—termed thermal curved-fragment (TCF)—exhibits statistically distinct, quantitative evidence of the confluence of human-knapped stone tools and exposure to a high-energy, long-duration, ground-level fire (i.e., campfires). Experimental TCFs are described and compared to unfired knapping debitage, natural exfoliations and suspected archaeological TCFs. The provenance of these archaeological specimens has previously been argued to infer hominin-controlled fire at 1.5–1.6 Ma at the Koobi Fora Formation. We also present data from experiments exposing stone flakes (arranged as “scatters”) of similar raw materials to those found in the Koobi Fora Formation to USDA prescribed burns in a variety of conditions approximating landscape fires. Results indicate that TCFs are formed specifically where (previously) knapped stone is exposed to high-energy ground level fires, similar to those seen in ethnographic campfires. Our analysis indicates that TCFs can be used in conjunction with other lines of evidence indicating the presence of anthropogenic fire in the archaeological record.