Actualistic research into dynamic impact and its implications for understanding differential bone fragmentation and survivorship

The relationship between bone mineral density and archaeological bone survivorship has played a critical role in zooarchaeological and taphonomic studies in recent decades. Numerous studies have suggested that higher-density skeletal element portions survive more frequently than lower-density element portions when archaeological assemblages are affected by some taphonomic processes. Interpretations of density mediated destruction have become commonplace in the archaeological literature, and are often used to explain the absence of certain bone elements and element parts in zooarchaeological assemblages. This study explores the effects of rockfall on bovid elements in varied environmental conditions and the differential survivorship of their element parts, and has implications for understanding the taphonomic processes through which bones are subjected to dynamic loading. Actualistic rockfall experiments conducted on twelve samples of frozen, fresh, and semi-dried bovid bones reveal that the generally low-density epiphyseal ends of bone elements resist fracture and analytical deletion with more frequency than the higher-density diaphyses. This evidence suggests that bone density does not correlate with likelihood of breakage or effective archaeological “destruction” when rockfall and other processes that result in dynamic impact are in action. While this research does not question the relationship between bone mineral density and the likelihood for archaeological survivorship as the result of some taphonomic processes, it presents one specific set of taphonomic processes that result in the differential survivorship of low density bone elements parts and the fragmentation and destruction of higher density element parts. This research presents evidence that shows that dynamic impact is a process capable of fragmenting and sometimes destroying high-density elements while low-density elements survive.     

Bone Mineral Density of Wild Turkey (Meleagris gallopavo) Skeletal Elements and its Effect on Differential Survivorship

Zooarchaeologists recognize that density-mediated attrition is a bias that demands consideration in the analysis of archaeofaunal samples. This paper presents bone mineral density values (aereal and volumetric) for the wild turkey (Meleagris gallopavo) and represents the first application of Dual-energy X-ray Absorptiometry (DEXA) to birds. The relationship between density and the survivorship of avian skeletal elements and portions is demonstrated by examining 20 assemblages from the archaeological record of the northeastern United States. The results suggest that density may account for the differential survivorship of least 35% of the samples tested. Further analysis of a single site demonstrates the importance of examining bone mineral density when interpreting past bird hunting and use.     

The relationship of bone mineral density and other growth parameters to stress indicators in a medieval juvenile population

In this study the radii of 34 juveniles from Wharram Percy, a British medieval site, were measured for bone mineral density (BMD) using dual energy X‐ray absorptiometry (DXA) in order to investigate evidence of stress including Harris lines, cribra orbitalia and deficient cortical index, which is usually attributed to poor nutrition. BMD measurements are used in modern children to assess growth and development and generally correlate with linear growth. Only rare chronic illnesses affect bone mineral accrual in children. Radiographs of the radii were examined to assess cortical index and of the femora and radii for Harris lines. The results indicate that BMD is well correlated with dental age and linear growth, but is poorly correlated with cortical index. The variability in cortical index indicates the influence of environmental factors. There is no relationship between BMD and the presence or absence of Harris lines or cribra orbitalia. Thus, despite obvious evidence of skeletal stress in this juvenile population, bone was not under‐mineralised and bone mineral accrual proceeded normally with growth. This reinforces the conclusion that cortical index is a more sensitive indicator of environmental stress than either Harris lines or cribra orbitalia, and may be compared with BMD measurements to assess the effect of stress on growth. Copyright © 2005 John Wiley & Sons, Ltd.     

Baboon Bone Mineral Densities: Implications for the Taphonomy of Primate Skeletons in South African Cave Sites

C. K. Brain (e.g., 1981) documented an interesting difference in relative skeletal part representation between primates and bovids of similar live body size recovered from the fossil cave site of Swartkrans (South Africa). Hominids and baboons are represented primarily by skull parts and a paucity of postcranial bones, while small sized bovids (Size Classes 1 & 2) are represented by more equivalent abundances of all skeletal elements. Brain argued that the Swartkrans bones were primarily carnivore collected, and postulated that the difference in element frequencies between primates and bovids is the manifestation of less durable primate postcranial skeletons relative to those of bovids when either are subjected to a destructive process such as carnivore feeding. Experiments by Brain (1981) in which baboon and bovid carcasses were fed to large, African carnivores lend support to this hypothesis. Bovid postcranial elements survived carnivore feeding more frequently and more completely than those of primates. Assuming that bulk bone mineral density (bulk BMD) is a measure of durability, we supplement Brain's observational data by presenting the first systematic, element-by-element comparison of baboon and bovid postcranial bulk BMD measurements obtained by dual energy X-ray absorptiometry (DXA). While the bovid in our sample exhibits greater absolute bulk BMD values in 57·8% of all measured bone areas, when grouping areas by body region, a statistically significant difference in absolute bulk BMD values between the baboons and bovids is documented only in the hindlimb region (i.e., femur, tibia and patella). Density differences in other body regions are not statistically significant. Further, in only one case (i.e., small bovids in the Member 2 [1948–1953/1965–1975 excavation] assemblage) is there a significant and positive correlation between skeletal part frequencies of primates or bovids and bulk BMD. This suggests that, for the most part, primate and bovid skeletal part representation at Swartkrans is not the result of density-mediated processes. Differences in skeletal part representation between primates and bovids at Swartkrans may thus be attributable to factors other than bone density—such as bone size, length, shape, and/or the relative palatability of surrounding soft tissues on bones.     

Raw Material Availability and Technological Choice: Modified Metapodia from an Early Bronze Age Site in Central Israel

This paper explores the incongruous relationship between bone raw material availability and technological choice at the Early Bronze Age site of Horvat 'Illin Tahtit (HIT) in central Israel. At HIT, the worked bone assemblage is mostly comprised of minimally modified sheep and goat metapodia whose function(s) are enigmatic. Most specimens have longitudinally oriented scraping abrasions on at least one face, and of these, some have bilaterally symmetrical drilled perforations on the distal–posterior face. Furthermore, the distal epiphyseal plates of almost all worked metapodia are unfused, whereas unfused epiphyses are nearly absent from the general faunal assemblage. Worked goat metacarpals are significantly more common than sheep metacarpals or metatarsals of either species, despite the greater abundance of sheep over goat in the general faunal assemblage. This paper proposes that the desire to express specific visible attributes of the bone raw material was the key motivation in choosing unfused goat metacarpals over similar, more abundant choices. The analysis considers material properties such as bone mineral density and natural morphology and concludes that material properties between various choices were equivocal. This result suggests that social meanings attributed to specific animals and specific skeletal elements structured bone raw material procurement decisions. Copyright © 2011 John Wiley & Sons, Ltd.     

Skeletal element abundances in archaeofaunal assemblages: economic utility,sample size,and assessment of carcass transport strategies

Economic utility indices provide a means of interpreting butchery and transport decisions reflected in the relative abundance of skeletal elements. Because of destructive taphonomic processes, interpreting skeletal element abundances in terms of carcass transport strategies requires that faunal analysts consider only those elements which accurately reflect their original abundances following human discard. In this study we use resampling techniques to examine the impact of sample size on correlations between high-survival skeletal element frequencies and economic utility in four simulated population assemblages reflecting distinct carcass transport strategies. Correlations alone do not accurately reflect the true relationship between bone abundance and economic utility as particular transport strategies have a tendency to generate high frequencies of Type II errors as sample size decreases. We show that the Shannon evenness index can be used as a quantitative means of distinguishing between bone assemblages characterized by subtle variations in skeletal element abundances. The evenness index can also be used to evaluate whether observed correlations reflect sampling error. Results from our simulations are applied to three published faunal assemblages to evaluate likely carcass transport strategies.     

Osteoporosis among ancient Egyptians

Osteoporosis is a condition of reduced total bone mass per unit volume for the normal ratio of bone mineral to bone matrix. The present work deals with the investigation and evaluation of osteoporosis in ancient Egyptians of two social classes from the Old Kingdom in Giza. The aims of this study are to provide information about the lifestyle and health status of ancient Egyptians, and to detect the causes of osteoporosis. The material consisted of 74 skeletons (43 males and 31 females) from two different social classes (high officials and workers). Skeletons were excavated from the Giza Necropolis and belonged to the Old Kingdom (2687–2191 BC). Dual energy X‐ray absorptiometry (DEXA) was used to measure bone mineral density (BMD) at different skeletal sites (radius, fourth lumbar vertebra and head of femur). Moreover, scanning electron microscopy (SEM) was used to show the microarchitectural structure of the bone. Results showed a significant decrease of BMD values in old age groups compared with younger ones in both sexes. In addition, SEM of trabecular bone in osteoporotic cases demonstrated that the horizontal trabeculae were more affected than the vertical trabeculae. Comparison between high officials and workers revealed that osteoporosis was more frequent in male workers than in male high officials, and in female high officials than in female workers. An elevated prevalence of osteoporosis among male workers may be related to the effects of nutritional stress and excessive workload, while a sedentary lifestyle may have played a role in the occurrence of osteoporosis among female high officials. Moreover, osteoporosis occurs earlier and more frequently in females than males, which may be related to the hormonal changes that accompany the menopause in females. This study emphasises the importance of gender and lifestyle factors in influencing the severity of osteoporosis. Age‐related bone loss at most skeletal sites is noted in both sexes of ancient Egyptians. Copyright © 2008 John Wiley & Sons, Ltd.     

Age-dependent bone loss in the femur in a medieval population

Age-dependent bone loss in femurs in a medieval skeletal assemblage from Wharram Percy, England was studied. Dual energy X-ray absorptiometry (DXA) was used to measure bone mineral density (BMD) in the proximal femur; radiogrammetry was used to measure cortical index (FEMCI) at the femur mid-shaft. Age-related loss of BMD was found in the proximal femur in both sexes. Females but not males showed loss of FEMCI. Patterning in bone loss with respect to age, sex and site in the skeleton resembled that seen in recent subjects. In this respect the results are similar to those of a previous study of metacarpal cortical bone in the same archaeological assemblage. Given the large difference in lifestyles, and that lifestyle factors are widely held to influence the severity of bone loss in osteoporosis, the similarities between the medieval and modern populations in the patterns of bone loss are surprising. These findings support those from an earlier study of these skeletons in calling into question the role of lifestyle factors in influencing the severity of bone loss in osteoporosis. © 1998 John Wiley & Sons, Ltd.     

Metapodial asymmetry in draft cattle

Traction work by oxen has been well documented in various pictorial and written sources throughout human history. Analysis of metapodial dimensions has been carried out with the aim of quantifying asymmetry related to sexual dimorphism, body size and possibly heavy duty traction work. A modern reference sample of 103 animals from Hungary and Rumania has been used for this purpose. Bone measurements were correlated with bone density and morphological characteristics in order to make the results applicable for the identification of remains from draft cattle in archaeozoological assemblages. Asymmetry is more pronounced in the thoracic extremity and metacarpals of older or heavier animals, sometimes showing excessive widening of the third, medial ray within the fused bone. Relative broadening is also intensive in the distal end of medial metatarsals of cows and oxen. The bone mineral content of the medial carpal region attains mature density first. The weight of phalanges increases for a longer time in the laterally located toes.     

Variation in tooth mark frequencies on long bones from the assemblages of all three extant bone-collecting hyaenids

Tooth mark frequencies on long bones are examined from the assemblages of all three extant bone-collecting hyaenids. Comparisons are made with a recent study examining tooth mark frequencies and possible sources of variation from a single spotted hyaena (Crocuta crocuta) assemblage (Faith, J.T., 2007. Sources of variation in carnivore tooth-mark frequencies in a modern spotted hyena (Crocuta crocuta) den assemblage, Amboseli Park, Kenya. Journal of Archaeological Science 34 (10), 1601–1609). The factors that may influence tooth mark frequencies are fragment size, fragments from different sized animals, region of skeletal element and bone density. All four factors are examined in the present study and compared across species and with previous results. The results indicate that there is a great deal of variation in tooth mark frequencies not only between the species but also from the same species.     

Differential Avian Skeletal Part Distribution: Explaining the Abundance of Wings

An abundance of wings relative to other skeletal parts has been observed in avifaunal assemblages from many different types of archaeological sites from numerous locations around the world and of various time periods. Both cultural and post-depositional hypotheses have been proposed to explain this pattern. One of the most powerful explanations to account for this phenomenon is differential survival of avian elements due to bone density. Although bone density has not been systematically measured for all types of birds, I test this hypothesis using predictions derived from observations about the functional anatomy of birds using archaeological data from numerous sites in the Pacific Northwest Coast (U.S.A.). I conclude that the density hypothesis is not supported at these sites, and that other hypotheses must be examined further.     

Osteometric and molecular sexing of cattle metapodia

Sex identification of skeletal remains based on morphology is a common practice in Zooarchaeology. Knowledge of the sex distribution of slaughtered or hunted animals may help in the interpretation of e.g. hunting or breeding strategies. Here we investigate and evaluate several osteometric criteria used to assess sex of cattle (Bos taurus) metapodia using molecular sex identification as a control of the metric data. The bone assemblage used to assess these new criteria derives from the Eketorp ringfort in the southern parts of Öland Island in Sweden. One hundred metapodia were selected for molecular analysis of sex and we were able to genetically identify the sex of 76 of these elements. The combined results of the molecular and osteometric analyses confirm a significant size difference between females and males for several measurements for both metacarpals (Mc) and metatarsals (Mt). Our results show that some measurements are applicable for metapodials. These measurements include the slenderness indices such as the Mennerich’s index 1 and 3, as well as the distal breadth (Bd), the breadth between the articular crests (Bcr), and the maximum breadth of the lateral trochlea (BFdl). We show that they can be used for sexing of both metacarpals and metatarsals. The latter measurements offer an opportunity to study fragmented elements and thus a higher number of elements may be utilized for morphological sexing of archaeological bones. Size comparisons of Mc and Mt may also aid in the separation of bulls and oxen.     

Gazelle bone marrow yields and Epipalaeolithic carcass exploitation strategies in the southern Levant

We measure the bone marrow yields of mountain gazelle (Gazella gazella) carcasses to reconstruct gazelle exploitation strategies during the Epipalaeolithic periods in the southern Levant. We present experimentally derived data on the bone marrow content of seven fresh gazelle carcasses, determine the range of marrow yields among individuals of different sexes and seasons of death, and compare the new data to gazelle skeletal element abundances from five Epipalaeolithic assemblages from Israel. We found extensive variation in marrow fat content among individual gazelles. Animals with the highest marrow yields were killed in the spring while animals killed in the early autumn had lower fat contents. Nevertheless, our results suggest that gazelle marrow provided a reliable, albeit small fat resource for prehistoric foragers in all seasons. Strong relationships between bone fragmentation and marrow content demonstrate that Epipalaeolithic people preferentially processed bones with high marrow yields.     

Bone density determination of moose skeletal remains from Isle Royale National Park using digital image enhancement and quantitative computed tomography (QCT)

As part of an investigation of prey vulnerability in Isle Royale National Park, MI, digital image processing techniques were used to enhance original quantitative computed tomography (QCT) film products to detail the processes of bone resorption and reformation in skeletal remains of moose (Alces alces). Integration of these two allied imaging technologies allowed analyses of pixels representing fractions of millimetres of bone. Using regression analysis, linear conversions from the pixel digital numbers (DN) to QCT Hounsfield units (HU) to actual bone mineral density (BMD) values were calculated (r²=0.99), and a scale of pixels per millimetre of bone was determined. The colour-enhanced image revealed quantifiable patterns of density, porosity and asymmetry. In addition, the procedure provided a quick but consistent methodology for evaluating numerous scans. Combining the limited use of a high-demand and expensive medical QCT scanner with a lower cost, readily available digital image processing and analysis system provides a technique for researchers to investigate the bone integrity of individual animals and populations. This method of evaluating bone density has implications for use in determining differential skeletal part-preservation in archaeofaunal studies. © 1997 John Wiley & Sons, Ltd.     

Body Part Representation,Fragmentation and Patterns of Ertebølle Deer Exploitation in Northwest Zealand,Denmark

The faunal assemblages from Asnæs Havnemark, Fårevejle and Trustrup, located in northwest Zealand, Denmark, yielded extensive yet substantially fragmented bone material dating predominantly to the late Mesolithic Ertebølle culture, ca. 5400–3950 cal BC . This paper presents a combined assessment of skeletal part representation of red deer (Cervus elaphus) and roe deer (Capreolus capreolus) from these three sites in conjunction with quantification of overall fragmentation data for the assemblages. These data indicate that the observed pattern of skeletal part abundance is most consistent with a pattern of density‐mediated skeletal attrition, and therefore the whole carcasses were initially deposited. Deer were not part of a logistic exploitation strategy at these sites. This indicates variability during the Ertebølle period not only in which resources were exploited, but in how these resources were processed. Copyright © 2013 John Wiley & Sons, Ltd.     

FOCUS: on the use of the petrous bone for estimating cranial abundance in fossil assemblages

Low representation of braincase bones in zooarchaeological assemblages suggests that skulls have been intensively processed by Levantine Epipalaeolithic foragers; most cranial elements are often unidentifiable and are considered poor candidates for quantifying crania. In contrast, the petrous bone is usually found complete, and was found to be easily identifiable to body size category. Use of the petrous bone in fossil assemblages analyses leads to better estimation of the occurrence of cranial elements, and thus of skeletal part representation. We therefore suggest use of the petrous bone for detecting bone destruction and selective transport in faunal assemblages.     

New analytical methods for comparing bone fracture angles: A controlled study of hammerstone and hyena (Crocuta crocuta) long bone breakage

Accurate interpretation of the cause and timing of bone breakage is essential for understanding the archaeological record. However, many variables potentially influencing break morphology have yet to be systematically explored. Focusing primarily on hammerstone breakage, we introduce new analytical methods for comparing fracture angles using the absolute values of the angle from 90°. We systematically control for intrinsic variables such as taxon, skeletal element, limb portion and skeletal age. We also compare experimental assemblages of femora broken by hammerstone and spotted hyena (Crocuta crocuta). We show that fracture angles are influenced by breakage plane, skeletal element and limb portion. While the latter two have been suggested before, this is the first time the differences have been quantified. We suggest that researchers stratify their assemblages by these variables if they are using fracture angles in analyses. At the assemblage level, hyenas created more oblique fracture angles on oblique breaks than did hammerstones.     

An investigation of cortical bone loss and fracture patterns in the neolithic community of Çatalhöyük,Turkey using metacarpal radiogrammetry

Bioarchaeologists have conducted numerous studies on human skeletal remains using metacarpal cortical bone radiogrammetry. This method allows cortical thickness of the second metacarpal to be quantified. As a sensitive index of bone health metacarpal cortical thickness is evaluated in the context of functional adaptations, growth, ageing and bone loss in osteoporosis, as well as used as a reliable indicator of fracture risk. The focus of this study is an examination of the widely used calculation that expresses second metacarpal cortical bone values, followed by an examination of age and sex-related patterns of cortical bone loss and skeletal fragility fracture in a Neolithic archaeological skeletal sample from Çatalhöyük, Turkey. Using metacarpal radiogrammetry, 49 adult metacarpals (f = 27 m = 22) were examined. Data were collected for size variables, length (L) and total bone width (TW) as well as quantity variables, medullary width (MW) and cortical thickness (CT). These parameters were then used to calculate the widely used cortical index (CI) and two new indices expressing medullary width and cortical bone thickness in relation to length (medullary width index, MWI and cortical thickness index, CTI). The ratios were then used to explore age- and sex-related cortical bone loss and fragility fracture patterns amongst the inhabitants of Çatalhöyük. Çatalhöyük males and females demonstrate an inverse relationship where CTI decreases as age and MWI increase. Analyses indicate statistically significant age-related change in MWI amongst the oldest females. Despite age-related loss of bone, no typical fragility fractures are observed. We discuss the role of ageing and lifestyle factors at Çatalhöyük that may have been beneficial to skeletal health and a reduction in the risk of fragility fracture.     

Why are cut mark frequencies in archaeofaunal assemblages so variable? A multivariate analysis

Cut mark frequencies in archaeological faunal assemblages are so variable that their use has recently created some skepticism. The present study analyses this variability using multivariate statistics on a set of 14 variables that involve differential skeletal element representation, fragmentation processes, carnivore ravaging impact, carcass size and tool type. All these variables affect the resulting cut mark frequencies reported in archaeological sites. A large sample of archaeofaunal assemblages has been used for this study. It was concluded that the best estimator of cut mark frequency in any given assemblage is the percentage of cut-marked long bone specimens (probably due to its better preservation than other anatomical areas), which is determined by fragmentation and carnivore ravaging. Carcass size and tool type also play a major role in differences in cut mark frequencies. Fragmentation is also a key variable determining the abundance of cut-marked specimens. It is argued that general cut mark percentages are of limited value, given the number of variables that determine them, and that a more heuristic approach involves quantifying cut marks in a qualitative manner.     

South American camelid bone structural density: what are we measuring? Comments on data sets,values, their interpretation and application

Bone mineral data are used in archaeology to evaluate density mediated attrition or differential preservation of archaeofaunas. For South American camelids, there are different data sets of bone mineral content. To evaluate their utility, these data sets were applied to the analysis of density mediated destruction of five archaeofaunal assemblages from Formative Period archaeological sites in the southern Calchaquíes valleys (Catamarca, Argentina) in order to evaluate interpretations achieved as an ‘end user’. Both inter- and intra-bone element density related survivorship analyses are made, concluding that for fine grain studies more complete data sets and specific analysis are required.