Investigating the potential of micro-focus computed tomography in the study of ancient bone tool function : results from actualistic experiments.

Many experiments have sought to recreate the types of damage that would be expected in ancient stone and bone weapon tips. This damage is usually presented as visible fractures or microscopic surface modification. Fatigue tests conducted on bovine bones, however, show the development of internal micro-cracks that result from stress, prior to actual breakage. In this paper I present the results of an experimental investigation of bone points subjected to a variety of activities. I assess the presence of microdamage using micro-focus computed tomography. The results show that two patterns of microcracks develop in bone and are best viewed in longitudinal section. Micro-cracks are a cumulative feature dependent on the amount of load applied and the duration of activity. When subjected to high enough loading rates, micro-cracks will merge together to eventually form a fracture. Although further tests are needed to confirm the exact point at which these fatigue fractures begin to form, micro-focus computed tomography has the potential to reveal whether an individual bone point underwent multiple or prolonged impacts and thus to elucidate the probable function/s of ancient pointed bone tools where no visible damage is apparent. Micro-focus computed tomography is a non-destructive and non-invasive procedure and therefore safe to use on archaeological artefacts

Use-trace analysis of bone tools : a brief overview of four methodological approaches

In comparison with some other parts of the world, there has been a marked lack of engagement with the functional study of bone tools in southern Africa. Only a handful of researchers are actively conducting work on this important aspect of material culture on the subcontinent. In this paper, I explore four avenues of use-trace analyses that can be used to investigate the past function of bone tools, namely, use-wear, macrofracture analysis, morphological residues studies and micro-focus computed tomography. Despite the increasing application of sophisticated analytical software, definitions of use-traces still differ among analysts. Here I provide a brief overview of various use-trace indicators and descriptions of how to identify them. Wherever possible, I use only the consensus definitions and descriptions of the various use-traces for easier identification by a non-expert

Identifying animal taxa used to manufacture bone tools during the Middle Stone Age at Sibudu, South Africa: results of a CT‐rendered histological analysis

Abstract: This paper presents the histological characterisation of a selection of worked bone artefacts from Middle Stone Age layers at Sibudu cave, South Africa. Histographic rendering is achieved using highresolution Computed Tomography, which is non‐destructive and facilitates three‐dimensional histologic analysis. Excellent congruency in image quality was achieved with previous studies using this method. The results show that most of the artefact fragments contain mostly primary lamellar tissue, which is the bone tissue best adapted to withstand impact stresses. This indicates that bone with greater elastic properties was chosen. Histological characterisation allows the identification of animal taxa. Based on the sample analysed in this paper, Perissodactyla bone was used predominantly in the older layers at the site. Artiodactyla are represented throughout but appear far more frequently in the later (post‐Howiesons Poort onwards) layers. Some of the Artiodactyla specimens have high proportions of Haversian tissue, reducing elasticity. The higher percentages of Haversian tissue in the post‐Howiesons Poort artefacts relative to Holocene examples from southern Africa suggests that people may have started experimenting with bone from different animal taxa at this time and had not yet learned to eliminate the mechanically weaker secondary tissue. Apart from mechanical considerations, possible cultural constraints governing raw material selection is also explored

Results of utilitarian and accidental breakage experiments on bone points

In this paper, we present the results of two new experiments that assess the formation of macrofractures on bone tools subject to non-hunting-related activities. Our experiments were designed to assess the formation of macrofracture types that develop on bone tools that have been accidentally dropped and those that have been used in domestic activities, in this case, hide piercing. Whilst acknowledging that macrofracture analysts should take into account a margin of error when interpreting macrofracture results, our results suggest that the classification criteria for potential bone-tipped hunting weapons be refined to exclude all fractures other than spin-off fractures larger than 6 mm. We concur with other researchers that macrofracture analysis, while constituting a heuristically profitable tool, should be used as part of a multi-analytical approach

Southern African arrow poison recipes, their ingredients and implications for Stone Age archaeology

Abstract: Biochemical analyses of residues preserved on ethno-historical and archaeological artefacts increase our understanding of past indigenous knowledge systems. The interpretation of biochemical traces is, however, difficult. Problems that can hamper credible interpretations of ethno-historical or archaeological residues include incomplete knowledge about local natural products, limited published data about product applications, and overestimation of the abilities of the analytical techniques to make specific identifications. In an initial attempt to address some of the challenges, we discuss arrow poison as a case in point, and we provide complete, updated inventories of known southern African poison ingredients and recipes, suspected poisons, and the current state of knowledge about these toxins and their effects. We also suggest that discoveries of ancient arrow poison, and the technical steps involved in early toxicology, have the potential to indicate levels of human cognition

The perception of gloss : a comparison of three methods for studying intentionally polished bone tools

Abstract: Polished bone and stone tools are well known from many archaeological contexts. In use-wear studies, polish is usually characterised by the degree of surface roughness, or more subjectively by its visual appearance. Visual appearances, however, may be deceptive, and the scale of analysis of traditional surface roughness studies is often too fine to consider the overall visual effect of a polished surface. Here I consider three techniques for characterising modified bone surfaces and assess the correlation between surface roughness and gloss. My results show that softer contact materials generally produce higher gloss values than harder materials, but within these two broad categories results are more complex. Based on these experimental results a trial assessment is presented of archaeological bone tools from assorted Holocene sites. The ability to perceive and appreciate polished surfaces is linked to developments in the superior temporal sulcus region of the human brain, which is the same region in which our ability to perceive shapes and colour developed. Deliberately polished bone tools from Pleistocene contexts therefore have the potential to provide insights into cognitive developments in our species. The specular reflectance or gloss of a polished surface provides a quantifiable and repeatable measure, more suitable than surface roughness analysis, for characterising deliberate polish, although a combined approach is advocated

An experimental investigation into the origin of incised lines on a 4000-year-old engraving from Wonderwerk Cave, Northern Cape Province

An experimental investigation into the origin of incised lines on a 4000-year-old engraving from Wonderwerk Cave, Northern Cape Provinc

The evolution of bone points as hunting weapons in South Africa

The use of formally fashioned bone points as possible components in hunting weaponry has been seen as a marker of behavioural modernity. Unfortunately, their interpretation as hunting weapons, up to now, has been based on morphological analogy with recent hunter-gatherer artefacts. Many studies conducted over the last 30 years have focused on identifying criteria that can be used to establish the function of stone points. There have been no similar macro-fracture studies conducted on bone points thought to have been part of complex weapon systems. This study aims to combine the morphological approach to studying bone points, with macro-fracture analysis. Macro-fracture analysis has been successfully used to discern pointed stone tools that were subjected to longitudinal impact, the most likely cause of which is hunting. This approach was adopted to test whether the same technique is applicable to bone points and whether the bone points that are found in the archaeological record, as far back as c. 77 ka ago at Blombos Cave, were used as hunting weapons. The study involved the replication of a range of bone points that were used in an experiment designed to cause impact consistent with that of hunting scenarios. The experiment tested hand-thrust and mechanically projected bone points. The results of this experiment showed that macro-fractures develop similarly on bone points as on stone points. The morphological study of bone points from one ethnographic collection and eight archaeological assemblages, spanning Middle Stone Age (MSA) and Later Stone Age (LSA) periods, confirmed an earlier observation made in the Cape – that there may be some degree of patterning in the overall dimensions of bone points across the landscape. Furthermore, the study showed that all the bone points from MSA assemblages, with the exception of Blombos Cave, fall within the size range of ethnographic arrow tips. The results of the macro-fracture analysis on archaeological and ethnographic samples suggest that bone points from the MSA levels at Blombos, Peers and Sibudu Caves may have been subject to longitudinal impact and as such could have used for hunting purposes, but whether they functioned as part of spears or arrows remains uncertain

Further evidence for bow hunting and its implications more than 60 000 years ago : results of a use-trace analysis of the bone point from Klasies River Main site, South Africa

Abstract: The bone point (SAM 42160) from >60 ka deposits at Klasies River Main Site, South Africa, is reassessed. We clarify the stratigraphic integrity of SAM 42160 and confirm its Middle Stone Age provenience. We find evidence that indicates the point was hafted and partially coated in an adhesive substance. Internal fractures are consistent with stresses occasioned by high-velocity, longitudinal impact. SAM 42160, like its roughly contemporaneous counterpart, farther north at Sibudu Cave, likely functioned as a hafted arrowhead. We highlight a growing body of evidence for bow hunting at this early period and explore bow-and-arrow technology might imply about the cognition of people in the Middle Stone Age who were able to conceive, construct and use it

Potential for identifying plant-based toxins on San hunter-gatherer arrowheads

The antiquity of the use of hunting poisons has received much attention in recent years. In this paper we present the results of a pilot study designed to detect the presence of organic compounds, typically of less than 1200 Da, from poisonous plants that may have been used as hunting poisons in the past. We used ultra-performance liquid chromatography connected to a Synapt G2 high-resolution MS-QTOF mass spectrometer (UPLC-QTOF-MS) to provisionally identify plant-based toxins present in (1) extracts of fresh plant material, (2) a blind control recipe consisting of three plant ingredients and (3) a Hei||om arrow poison of unknown ingredients. Although not all expected toxic compounds were identified, those that were identified compared favourably with those reported in the literature and confirmed through databases, specifically the Dictionary of Natural Products and ChemSpider. MS/MS fragmentation patterns and accurate mass were used for tentative identification of compounds because archaeological residues usually contain insufficient material for unambiguous identification using nuclear magnetic resonance. We highlight the potential of this method for accurately identifying plant-based toxins present on archaeological artefacts and unique (albeit non-toxic) chemical markers that may allow one to infer the presence of toxic plant ingredients in arrow poisons. Any chemical study of archaeological material should consider the unique environmental degradative factors and be sensitive to the oxidative by-products of toxic compounds