Bone density studies in zooarchaeology

Accurate bone density data are essential for assessing the influence of destructive processes in archaeological faunal assemblages. Unfortunately, the diversity of methods employed by different researchers to derive density values has resulted in recent confusion. Two recent publications in this journal [J Archaeol Sci 29 (2002) 883; J Archaeol Sci 29 (2002) 979] exemplify this state of misunderstanding. Both studies argued that the role of bone density in shaping archaeological faunal assemblages has been largely overrated, but both based their conclusions on density values that were inaccurately derived. The former employed a method of calculating bone density that has been largely discredited over the past decade [J Archaeol Sci 29 (2002) 883]. Within a larger discussion of zooarchaeological methodology, the latter provided an assessment of the current state of bone density research that inappropriately characterized the discrepancies between available sets of density data as a reflection of the differences between two technologies—photon densitometry and computed tomography [J Archaeol Sci 29 (2002) 979]. The actual dichotomy exists—irrespective of the technology employed—between studies that account for variation in the shape of bone cross-sections and those that do not. The different sets of density data currently available to zooarchaeologists vary tremendously in their accuracy. We review and evaluate the different techniques employed in the research of bone density patterns of mammalian fauna. Computed tomography produces the most accurate density data. For elements without medullary cavities, photon densitometry may provide density values of similar accuracy but only if a method of cross-sectional shape-adjustment is applied.     

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.     

Population density functions: a differential equation approach

"This paper introduces a new mathematical technique to describe population density functions. Two length scales, which characterize the variation of these density functions within a region, are identified. A differential equation is derived and asymptotic solutions obtained. Two specific techniques, the method of matched asymptotic expansions and the method of multiple scales, are introduced and illustrated by application to population densities at both the metropolitan and regional levels."     

Stable isotopes,diet, and taphonomy: a look at using isotope-based dietary reconstructions to infer differential survivorship in zooarchaeological assemblages

Archaeology has always faced the problem of making informed inferences based on an incomplete record. Zooarchaeological studies of prehistoric hunting and diet offer a clear case in point, where a range of behavioral and taphonomic factors can produce a substantial disconnect between what people actually captured and ate and what archaeologists recover and interpret. We explore this disconnect by presenting stable C and N data for wild faunas, archaeological maize, and three human burials from Fremont-period sites in southeastern Utah, the United States. We use these data to estimate faunal contributions to prehistoric diets and compare the results with previous zooarchaeological analyses of faunas from the same sites. Results for the two approaches differ sharply, with isotopic estimates showing much higher contributions of small and lowland game. We discuss these results in terms of both local prehistory and wider issues of taphonomy and dietary analysis.     

Bone frequencies: differential transport, in situ destruction,and the MGUI

Human transport of bones with high food values, and destruction of bones with low density values are the traditionally invoked explanations of the frequencies of bones in archeological contexts. The manner in which these two explanations have been used suggests archaeologists assume the explanations to be independent of one another. The transport explanation is operationalized as the modified general utility index (MGUI) of Binford, and the destruction explanation is operationalized with measures of bone density. Statistical correlation of the MGUI with bone density, while weak, indicates that many high utility bones have low density values while many low utility bones have high density values. Because low density bones tend to be destroyed more readily than high density bones, inferences of human utility strategies derived from bone frequencies and based on the MGUI may be inaccurate. The utility strategies suggested by three archaeofaunas are compared to bone density, and two of these faunas are shown to potentially be the result of differential destruction and not human transport as measured by the MGUI.     

Modern and fossil charcoal: aspects of structure and diagenesis

The structures and compositions of modern and fossil charcoal samples were compared in order to evaluate charcoal degradation processes in archaeological sites. Modern charcoal samples produced in campfires contain two major phases: graphite-like microcrystallites and a non-organized phase. These phases create a mosaic-like structure with differing relative proportions depending on the taxonomic source of the wood used. Fossil charcoal samples (Tel Dor, Israel: 3000 years BP and Kebara Cave, Israel: 40,000 years BP) also contained the graphite-like microcrystallites and the non-organized phases, but were clearly altered compared to modern charcoal. The graphite-like phase of the fossil charcoal has much higher electrical resistivity, and its ESR properties show that it has markedly altered surface electronic states. Infrared spectra show the presence of additional carboxylate groups. Oxidation has therefore altered the structure. This appears to be a “self-humification” process that affects the graphitic component, and probably the non-organized phase as well.     

First soft-bodied fossil from the Ordovician of Peru

Konservat-Lagerstätten are a source of insurmountable information on the diversity of fossil assemblages during the lower Palaeozoic. Soft-bodied fossils are especially rare in South America, but a new locality has been discovered from the Middle Ordovician of Peru that has produced the fairly well-preserved possible palaeoscolecidan Juninscolex ingemmetianum gen. et sp. nov. The distinctive characteristics of this worm make it similar to European taxa within the group.     

Radiocarbon method in monitoring of fossil fuel emission

The traditional radiocarbon method widely used in archaeology and geology for chronological purposes can also be used in environmental studies. Combustion of fossil fuels like coal, natural gas, petroleum, etc., in industrial and/or heavily urbanized areas, has increased the concentration of carbon dioxide in the atmosphere. The addition of fossil carbon caused changes of carbon isotopic composition, in particular, a definite decrease of ¹⁴C concentration in atmospheric CO₂ and other carbon reservoirs (ocean and terrestrial biosphere), known as the Suess effect. Tree rings, leaves, as well as other annual growing plants reflected the changes of radiocarbon concentration in the atmosphere due to processes of photosynthesis and assimilation of carbon from the air. By measuring radiocarbon concentration directly in atmospheric CO₂ samples and/or biospheric material growing in industrial and/or highly urbanized areas where high emission of dead carbon is expected, it is possible to estimate the total emission of dead CO₂. Based on equations of mass balance for CO₂ concentration, stable isotopic composition of carbon and radiocarbon concentration it is possible to calculate CO₂ con-centration associated with fossil fuel emission into the atmosphere. The procedure use differences between the radiocarbon concentration and stable isotope composition of carbon observed in clean areas and industrial or/and highly urbanized areas.     

Ecydsial efficiency and evolutionary efficacy among marine arthropods: implications for trilobite survivorship

A comparison of ecdysial patterns between trilobites and other macrobenthic marine arthropods (crabs, shrimp, lobsters, horseshoe crabs) reveals differences that may have evolutionary consequences. Limulus and many malacostracans apparently have a signature ecdysial style; conversely, a range of moult configurations characterized trilobite ecdysis, and this variation is evident even within individual species. A canalised ecdysial habit may be safer or metabolically more efficient and therefore, summed over the history of the class, evolutionarily advantageous. Some trilobite clades show evolutionary trends toward morphologies that would have facilitated ecdysis (e.g. reduction in the number of thoracic segments, reduction in the number and prominence of spines), but co-adaptation or multiple-use effects complicate the evolutionary signal of ecdysial selection. Survivorship analysis supports a possible link between ecdysial habit and evolutionary success: genera with fewer thoracic segments (= easier ecydsis) are longer-lived. The increased predation pressure on trilobites through the Palaeozoic would have amplified the evolutionary impact of an inefficient moult habit. The cumulative effects of a less-than-optimal ecdysial habit, and a physiology that apparently required reconstituting a calcitic exoskeleton de novo with each moult, are compelling biotic factors to consider in examining functional interpretations, life histories, evolutionary trends, and ultimate disposition of the Trilobita.     

Mining,morality and the obligations of fossil fuel exporting countries

In this article I argue that countries exporting fossil fuels, such as Australia, have an obligation to bear some of the costs of the harms caused by the use of those fuels. I argue that there is an analogy between other harmful exports – medical waste, tobacco, unsafe jobs, uranium – and fossil fuels. If this is the case, then current methods for allocating emissions and responsibilities for their harms are inadequate and more complex than they appear. I consider several counter-arguments to this claim, such as that it does not recognise the benefits of coal and that exporters are not really responsible. Finally, I consider some of the consequences of this argument and claim that Australia and other fossil fuel exporters ought to have a higher ‘carbon budget’ if this argument is true and that exporters ought to bear a higher share of the costs of climate harms.     

Proboscidean die-offs and die-outs: Age profiles in fossil collections

Distinctive age profiles result from certain types of mortality processes that affect modern African elephants. Large collections of fossil proboscidean bones sometimes have similar age profiles—for example, those of the Lehner and Dent assemblages are identical to age profiles seen in modern drought-caused die-offs. Two other samples of mammoths (one from the Fairbanks muck deposits and one from a site near Waco, Texas) have age profiles suggestive of a stable age distribution in a mature population, resulting in the first case from long-term attritional mortality, and in the other case from sudden “catastrophic” mortality. Other fossil proboscidean age profiles that show high proportions of prime-age adults may have resulted from prolonged or recurring die-offs.     

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.     

Bone chemistry and paleodiet

Bone chemistry paleodietary studies are emerging as important research areas in archaeology, biological anthropology, and paleontology. With appropriate controls, the inorganic and organic chemical composition of bones and teeth can provide information about past diet and habitat use. Chemical signatures are used to address individual dietary variability in early hominid fossils, paleontological remains, and more recent human and faunal populations.     

水历是中华远古历法的“活化石”

水族民间流传的"苗甲子"以及"七元甲子"周,即以420序数为周期的历法是中国古代历法的"活化石"。     

First record of a fossil selenariid bryozoan in South America

López-Gappa, J., Pérez, L.M. & Griffin, M. February 2017. First record of a fossil selenariid bryozoan in South America. Alcheringa XX, xxx-xxx. ISSN 0311-5518.

Selenariidae Busk 1854 (Bryozoa) is considered endemic to Australia and New Zealand. Here we describe a new species of Selenaria Busk 1854 from the lower Miocene Monte León Formation (Patagonia, Argentina). Selenaria lyrulata sp. nov. is characterized by autozooids with a lyrula-like, anvil-shaped cryptocystal denticle, opesiular indentations and lateral condyles, as well as avicularia with a shield of fused costae. This is the first record of a selenariid bryozoan in South America.

Juan López-Gappa [lgappa@macn.gov.ar] CONICET—Museo Argentino de Ciencias Naturales. Av. Ángel Gallardo 470, C1405DJR, Ciudad Autónoma de Buenos Aires, Argentina; Leandro Martín Pérez [pilosaperez@gmail.com] and Miguel Griffin [patagonianoyster@gmail.com], CONICET—División Paleozoología Invertebrados, Museo de La Plata. Paseo del Bosque s/n, B1900FWA, La Plata, Argentina.