Taphonomic Variables Research Articles

Shell strength of Eucallista purpurata (Bivalvia) from life and death assemblages on sandy beaches of the Bonaerense coast, southwest Atlantic Argentina

ABSTRACT Mollusc shells are among the most abundant and well-preserved organisms in sediments worldwide, but their shells are usually subject to fragmentation due to exposure time in the TAZ, which compromises their preservation potential. The shell strength of valves from life and death assemblages from the sandy beaches of Santa Clara (37°50′49″S, 57°30′16″W) and Mar Chiquita (37°44′45″S, 57°25′1.5″W) on the Bonaerense coast, southwest Atlantic Argentina, was analysed to capture the effect of taphonomic processes over time and to determine how intrinsic properties and taphonomic variables influence their shell strength. To achieve this, the mechanical resistance profile of the bivalve Eucallista purpurata was assessed using point load and microindentation tests, and the mineralogical composition and organic matter content of the shell, as well as morphological variables, were measured. We concluded that, as expected, shells from life assemblages were more resistant to compression than those from death assemblages, but surprisingly, right valves were more resistant to compression than left valves in both Mar Chiquita and Santa Clara death assemblages. No differences were observed between broken and unbroken shells.

Autopsy doesn’t always tell all: The importance of exhuming skeletal remains of cemetery unidentified decedents

The process of personal identification differs according to the state of preservation of the corpse, becoming more complicated when dealing with remains altered by taphonomic variables. Since 2015, the staff of the Laboratory of Forensic Anthropology and Odontology (LABANOF) of the University of Milan has been engaged in recovering the skeletons of 36 unknown people from the cemeteries of the city of Milan, to redraw their biological profiles and give them back the possibility of being identified. Of the 36 starting skeletons, 7 have been identified and therefore are not the object of this study, 25 individuals were previously subjected to an autopsy examination and 4 skeletons were studied for the first time in the present work. The post-mortem data of all the individuals who had previously undergone autopsy and had not yet been identified (n = 25) have been retrieved from the archives of the Institute of Forensic Medicine in Milan and allowed for a comparison with those obtained from the new anthropological study of each exhumed skeleton. The authors aim to present the three most interesting cases to better highlight the results that emerged from the comparison. The autopsy information alone lacked important details. In all cases, the anthropological examination proved to be capable of detailing the biological profile of the unknowns even after a long period of inhumation (even more than 20 years). The limitations of instrumental investigations in achieving the goal single-handedly and the importance of recovering the unknown skeletons from cemeteries for identification purposes are discussed.

Turtles for the ancestors: A zooarchaeological study of ritual deposits on Fakahina, Tuamotu archipelago (French Polynesia)

AbstractRituals and feasting ceremonies at Polynesian marae depict culturally complex relationships between humans and animals that cannot be explained by subsistence alone. In Central‐East Polynesia, this topic still requires the elaboration of a “ritual zooarchaeology” framework. Using sea turtle assemblages from three sacred sites on Fakahina atoll (Tuamotu), this study offers a preliminary approach to faunal deposits from ritual contexts. Following systematic excavations of marae on Fakahina, analysis aimed to determine whether faunal deposits could be linked with intentional feasting and offering behaviours. To detect how ritual actions were organised through space, skeletal and taphonomic variables were examined for both overall sites and “sub‐assemblages” within sites based on the spatial associations of fauna with site features.At certain site features, derived quantitative units such as %MAU and recovery rate could identify potential offering behaviours through the intentional sorting of culturally significant body parts. The taphonomic signatures of site features could also identify open or closed deposition environments, assisting with the identification of disturbed features as either exposed platforms or enclosed cists. In addition to highlighting previously undocumented complexity in the use of site features, an overall comparison of turtle remains from the three sites shows the potential of these methods to explore variation in ritual practices.

Solving the inverse problem of post-mortem interval estimation using Bayesian Belief Networks

Bayesian Belief Networks (BBNs) can be applied to solve inverse problems such as the post-mortem interval (PMI) by a simple and logical graphical representation of conditional dependencies between multiple taphonomic variables and the observable decomposition effect. This study is the first cross-comparison retrospective study of human decomposition across three different geographical regions. To assess the effect of the most influential taphonomic variables on the decomposition rate (as measured by the Total Decomposition Score (TDS)), decomposition data was examined from the Forensic Anthropology Research Facility at the University of Tennessee (n = 312), the Allegheny County Office of the Medical Examiner in Pittsburgh, US (n = 250), and the Crime Scene Investigation department at Southwest Forensics in the UK (n = 81). Two different BBNs for PMI estimations were created from the US and the UK training data. Sensitivity analysis was performed to identify the most influential parameters of TDS variance, with weaker variables (e.g., age, sex, clothing) being excluded during model refinement. The accuracy of the BBNs was then compared by additional validation cases: US (n = 28) and UK (n = 10). Both models conferred predictive power of the PMI and accounted for the unique combination of taphonomic variables affecting decomposition. Both models had a mean posterior probability of 86% (US) and 81% (UK) in favor of the experimental hypothesis (that the PMI was on, or less than, the prior last known alive date). Neither the US nor the UK datasets represented any cases below 'moderate' support for the value of PMI evidence. By applying coherent probabilistic reasoning to PMI estimations, one logical solution is provided to model the complexities of human decomposition that can quantify the combined effect of several uncertainties surrounding the PMI estimation. This approach communicates the PMI with an associated degree of confidence and provides predictive power on unknown PMI cases.

Life and death at Dmanisi, Georgia: Taphonomic signals from the fossil mammals

There are many hypotheses regarding influences on the early hominin biogeographic spread into Eurasia; among them is increased meat-eating. Dmanisi in Georgia is one of the rare Early Pleistocene sites in Eurasia, and here we present primary information and analysis of the medium and large mammal taphonomy, contributing information about site formation and the hominins’ interaction with the fauna. Nearly 85% of the specimens come from the B1 stratum. Relative abundances of mammal families demonstrate some bias toward carnivores, especially Canis borjgali, and diverse Felidae species. Bones display little weathering. Post-depositional surface modifications and matrix obscure many bone surfaces, but carnivore tooth marking is the most common bone surface modification from the nutritive taphonomic phase. Tooth pits are large, in the size range of those made by modern Crocuta crocuta and Panthera leo. Breakage variables indicate most breaks occurred while the bones were still fresh, many by carnivore consumption. Fairly even limb bone representation of herbivores suggests carcasses were introduced to the site nearly whole. Hominin tool marks are present in low frequencies, but they suggest a variety of behaviors. These marks are found on Equus, Palaeotragus, Bison, large cervids, Pseudodama, Canis, and Mammuthus. Some were made by filleting proximal limb segments, and so are likely indicative of early access to carcasses, while other marks suggest scavenging. The Homo taphonomic variables resemble the rest of the taphonomic signatures from the site with little weathering, a slightly higher percentage of their bones are whole, but only a few have probable carnivore damage. The assemblage characteristics are compared to modern actualistic and experimental assemblages, and it is concluded that Dmanisi presents a palimpsest of hyena denning, felid activity, hominin meat-eating and likely natural deaths.

The rank abundance distribution of large-bodied vertebrates from Natural Trap Cave, Wyoming

Natural Trap Cave (NTC) is a well-known fossil locality located in Wyoming that contains a discontinuous record of sediments from the early Sangamonian (∼150 ka) to the present and produces a diverse vertebrate assemblage from 2-9 and 23–47 cal ka BP. This study examines changes in the rank abundance distribution (RAD) of NTC's large-bodied (>8 kg) vertebrates, to assess the stability of the local ecosystem surrounding the cave across the Late Pleistocene-Holocene transition. RADs were generated based on 2208 skeletal elements from four stratigraphic units, collected by Gilbert and Martin from 1974 to 1979. All bones included in this study had: a north-west grid coordinate, a known depth below the sediment surface, were over 20% complete and taxonomically diagnostic. Isotaphonomy was assessed using multinomial regressions of %MAU against multiple taphonomic variables: size, shape, degree of abrasion and weathering, fracture type, percent complete, original bulk density, and surface area to volume ratio. Changes in RADs were analyzed using rank abundance curves (RACs), Wilcoxon Rank Sums test, and kurtosis. RADs were also fit to a suite of standard ecological models (i.e., geometric, log-series, zero-sum multinomial, & log-normal) using maximum likelihood and the Akaike Information Criterion corrected for small sample size (AICc). The four faunal assemblages show little variation in taphonomic biasing, so any changes in the RADs reflects changes in the ecosystem. The four RACs showed little change in their shape or faunal composition and are dominated by a few abundant taxa, representing an ecosystem that experienced perturbations (i.e., a concave RAC and a kurtosis value > 3). The Wilcoxon Rank Sums test found no statistical difference among the RADs from the lower three stratigraphic units. This means that the abundance structure of the large-bodied vertebrates did not change prior to (35.8–25.3 cal ka BP) or during the Last Glacial Maximum (25.3–17.2 cal ka BP) and the local ecosystem surrounding NTC never approached equilibrium. The uppermost stratigraphic unit represented a mixed Late Pleistocene and Early Holocene assemblage, so changes in ecosystem structure from the Last Glacial Maximum to the Holocene (10.5 cal ka BP – present) cannot be evaluated. Unfortunately, the ecological models used in this study provide little insight into the maturity or processes influencing the formation of the local ecosystem surrounding NTC because only three models produced a ΔAICc value between 4.4 and 6.7.

Methods for collecting spore and pollen samples from city pavements and the palynomorph distribution in urban areas

To test the validity and reliability of methods for collecting palynological samples from paved surfaces common in urban areas, palynomorphs at three concentration levels were collected from four pavement types using seven different methods. Results showed that more spores and pollen could be recovered from smooth surfaces than from other surface types, while sterile water˗soaked cotton swabs tended to yield comparable results from almost all experiments. However, where spores and pollen occurred in high concentrations, nearly all tools produced similar palynological profiles. The forensic potentiality of palynomorphs distributed over 17 different urban locations was also investigated. A total of 99 palynomorph taxa were recovered. Each sampling site contained different palynomorph assemblages due to a vast number of taphonomic variables. These localised variations strongly support the forensic use of spores and pollen found in cities.

Contextual taphonomy for zooarchaeology: Theory, practice and select Levantine case studies

Contextual taphonomy is an archaeological approach that integrates taphonomic variables with stratigraphy and context, often at the intra-site level. A majority of zooarchaeological research explores vertebrate taphonomy broadly by entire temporal levels of sites, thus aggregating multiple contexts by time period. Yet, an increasing number of high-resolution studies go beyond this level to explore taphonomy per context or by other meaningful intra-site divisions. This approach marshals the rich information offered by the well-established discipline of taphonomy to build depositional histories of site features that contain bones, thereby revealing their formation and use. Here, we aim to better formalize the definition of contextual taphonomy for zooarchaeology and demonstrate its great applicability through select case studies in Israel. In this summary of the approach for the Special Issue on “Contextual Taphonomy in Zooarchaeological Practice”, we lay out the main requirements for multi-scalar contextual analysis and caution against potential pitfalls. Ultimately, archaeofaunal taphonomic studies at the context level are pertinent for myriad research questions, including those of refuse maintenance, camp organization and feasting.

Detection of Chemical Weapon Nerve Agents in Bone by Liquid Chromatography-Mass Spectrometry.

A recently proposed model for the incorporation of xenobiotics of forensic interest into the human skeleton suggests nerve agent metabolites may incorporate into bone at relatively elevated concentrations based on their unique chemical properties. To test the hypothesis that nerve agent metabolites interact with bone, methods for the extraction, isolation and semi-quantitative detection of nerve agent metabolites (MPA, EMPA, IMPA, iBuMPA, CMPA and PMPA, corresponding to the nerve agents VX, Russian VX, sarin, cyclosarin and soman, respectively) from osseous tissue were developed using liquid chromatography-mass spectrometry with both quadrupole time-of-flight and triple quadrupole (QqQ) instruments. The optimized methods were validated on the QqQ instrument. Despite high ion suppression, the achieved limits of detection (5-20pg/g for four analytes; 350pg/g for the fifth analyte) were lower than many of those published for the same analytes in other biomatrices, including serum and urine. These methods were tested on the skeletal remains of minipigs exposed to the chemical weapon VX in vivo. The VX metabolite was detected in multiple minipig bone samples; to the authors' knowledge, this is the first time in vivo nerve agent exposure has been detected from bone. Further, detected concentrations and diaphyseal-to-epiphyseal area count ratios reflect animal exposure history. Although the results are limited, they are promising, indicating that nerve agent metabolites may interact with bone as a pharmacokinetic compartment and can be extracted from bone postmortem. Additional studies, assessing the effects of different agents, exposure pathways and taphonomic variables, are needed; however, these results suggest the method may be used with human bone to detect use of chemical weapons from postmortem biomatrices even well after a suspected attack. More general implications for both nerve agent toxicology and skeletal toxicology are also discussed.

The river that never was: Fluvial taphonomy at Olduvai Bed I and II sites and its bearing on early human behavior

Olduvai site integrity has been questioned through interpretations of fluvial inputs on most assemblages from Beds I and II that rest on a contradictory use of taphonomic variables, lack of geological support, and lack of adequate experimentally-supported referential frameworks. Most variables used to address fluvial impact in faunal assemblages have been independently used in other contexts and all of them are subjected to variable degrees of equifinality. Their resolution when applied to archaeological assemblages is low. A more recent approach founded on experimentation simulating actual archaeological sites shows that it is the intrinsic properties of each bone specimen (i.e., composition and shape) that best determine the resistance of each bone to be moved by water, regardless of size. The application of this approach, which combines the relative representation of specimens according to their composition (i.e., texture: dense or spongy-trabecular or mixed) and shape (flat, tube, or cube-polyhedral), shows not only that fluvial inputs on bone assemblages can be well detected, but also that the scale and magnitude of such inputs can be efficiently assessed. Thus, site formation can be more accurately interpreted with the aid of these new experimental analogical frameworks. A selection of some of the most relevant Olduvai sites from Bed I and Bed II have been used to show that all represent autochthonous concentrations of fossil materials and that their potential fluvially-caused distortion was marginal in most sites and moderate (in the form of semi-lag assemblages) in just a couple of them. This reinforces the causality of biotic agents (i.e., hominins and carnivores) in the formation of these sites.

Patterns of soft tissue and cellular preservation in relation to fossil bone tissue structure and overburden depth at the Standing Rock Hadrosaur Site, Maastrichtian Hell Creek Formation, South Dakota, USA

Recovery of soft tissues and cells from fossil bones is becoming increasingly common, with structures morphologically consistent with vertebrate osteocytes, blood vessels, fibrous/collagenous matrix, and potential intravascular contents now recognized from specimens dating back to the Permian. However, it largely remains unclear how bone tissue structure, early diagenetic regimes, and many other taphonomic variables influence or control the preservation potential of soft tissues in vertebrate fossils. To explore the influence of a few of these factors, we tested a suite of fossils from the Standing Rock Hadrosaur Site, a vast Edmontosaurus annectens bonebed in the Maastrichtian Hell Creek Formation of South Dakota, for preservation of cellular and tissue components. Demineralization of bone samples from each specimen yielded abundant microstructures morphologically consistent with vertebrate osteocytes, blood vessels, and collagenous matrix. This includes the first recovery of osteocytes and vessels from a fossil vertebral centrum and ossified tendons. Perhaps surprisingly, no correlation was found between soft tissue/cellular recovery and either bone tissue structure type (cortical vs. cancellous) or overburden depth at the time of discovery. A traditional taphonomic survey of the site, conducted in parallel and reported previously, affords a clear and detailed history of these remains, both pre- and postburial. Cumulative taphonomic evidence indicates the Edmontosaurus individuals died in a mass mortality event and their disarticulated remains were buried rapidly in a shallow floodplain pond during a crevasse splay event. Oxygenated flood waters and/or groundwater oxidized initially sideritic concretions to goethite during early diagenesis, facilitating rapid cementation of portions of the sediment that likely aided stabilization of soft tissues by shielding regions of the bones from prolonged exposure to pore fluids. Our findings support cancellous bone as a viable target for cellular analyses, corroborate previous propositions that iron-rich environments and rapid burial facilitate soft tissue preservation, and provide new details into early diagenetic environments conducive to such preservation.

ACTUALISTIC NEOTAPHONOMIC RESEARCH ON BONE MODIFYING ANIMAL SPECIES: AN ANALYSIS OF THE LITERATURE

The volume of literature on taphonomic modifications to faunal remains created by a particular animal species in an actualistic neotaphonomic (ANT) context has grown rapidly since the 1960s. A sample of 454 investigations on the taphonomic traces created by bone modifying animal species published starting in 1911 and through mid-2018 includes studies of 115 species of mammal and 78 species of bird. The most frequently studied bone modifying mammal species is spotted hyaena (Crocuta crocuta) and the most studied bird is barn owl (Tyto alba). One-hundred seventy two of 609 individuals (28.2%) have authored more than one investigation. One-hundred eight of 417 texts (25.9%) compare faunal remains accumulated and modified by ≥ 2 species in an effort to establish signature criteria—modifications to carcasses and bones diagnostic of a particular bone modifying species. Two hundred and four texts (of 417 [48.9%]) document how one or more animal species modify bones, many with the unelaborated warrant that such documentation has paleozoological implications. Commonly reported variables include the kinds of modifications to bones (238 of 417 [57.1%] texts) and skeletal part frequencies (217 of 417 [52.0%] texts). Thoughtful consideration of taphonomic variables chosen for measurement and construction of interpretive models having dynamic sufficiency (the model includes the correct processes and variables to account for the field of inquiry), empirical sufficiency (included variables can be measured in the real world), and agreed upon tolerance limits (the model matches the empirical record sufficiently closely to be analytical useful) will enhance the value of ANT research.

The validation of ‘universal’ PMI methods for the estimation of time since death in temperate Australian climates

Forensic anthropologists have traditionally relied on their knowledge and experience of the decomposition stages to make an assessment of the time since death. However, recently new and empirical methods have been developed in various regions worldwide that propose to estimate the post-mortem interval (PMI) based on the observed decomposition changes alongside important taphonomic variables. Yet despite these methods being predominantly geographic specific, a number of methods have suggested they are effective universally and it is these ‘universal’ methods that have been inadequately test in Australia. The current study evaluated the accuracy of two of these methods in an Australian context, specifically the Greater Western Sydney region. The protocol developed by Megyesi et al. (2005) [1] was investigated because it is commonly cited in the literature and the PMI formula created by Vass (2011) [2] was also investigated because of its ‘universal’ claim. Between December 2014 and March 2016, two experimental trials were undertaken during the Australian summer seasons. Sixteen adult pig carcasses were left to decompose undisturbed on a soil surface common throughout the Western Sydney region and the Megyesi et al. (2005) [1] and Vass (2011) [2] methods were applied to the remains during this period. The results showed the Megyesi et al. (2005) [1] method overestimated the known PMI of remains, whereas the Vass (2011) [2] formula underestimated the time since death of the remains in these trials. The inaccuracy may be attributed to the constants which make up the variables in these formulas and they may not reflect the values of these variables in the Western Sydney region.

Fluvial spatial taphonomy: a new method for the study of post-depositional processes

Traditional taphonomic analyses do not consider the emergent properties resulting from the relationship of variables. Several of these emergent properties are expressed spatially. Here, we present a spatial taphonomic approach to the understanding of post-depositional processes affecting experimental assemblages modified by fluvial currents. Spatial statistical methods are a great tool to understand how different taphonomic variables relate at a spatial scale. The results of the application of this method to bone assemblages affected by low- and high-energy flows show the loss or modification of most of the original spatial taphonomic relationships. It also shows the degree of bone loss according to element, anatomical section and bone structure, and shape types. Anisotropy is identified in both experimental contexts. These results add new criteria to assess the impact of water flows in bone assemblages and contribute to define the properties of lag assemblages.

Microhistorias de la Prehistoria Reciente en el interior de la Península Ibérica

This paper presents the intellectual framework and outcomes of a research project designed to characterize the formation cycles of the archaeological record in later prehistoric Iberian Meseta or Central Plateau. Contrary to mainstream generalist discourses and grand histories, an inductive, particularistic and microscale approach is advocated. A multiple-case study was conducted, based on ceramic assemblages from eight sites (settlements, pit sites, monuments) ranging from the Early Neolithic to the Late Bronze Age (c. 5500-1100 BC). A total of 10,800 potsherds from assorted anthropogenic features (gullies, ditch, pits, tumuli, hut) were assessed according to a series of taphonomic variables (size, erosion, parent vessels) informing abandonment dynamics. A diachronic and comparative account drawing on these highly-detailed observations allows better ascertaining cross-cultural social practices (deliberate fragmentation, circulation and deposition of substances) and their currency. The results mostly comprise unintended material effects from heterogeneous processes dealing with everyday refuse management and some exceptional deliberate end products, more easily identified.

Variabilidad en conjuntos zooarqueológicos tempranos del Macizo del Deseado (Santa Cruz, Argentina)

The Zanjones Rojo and Blanco basin is located to the Northeast of the Deseado Massif (Santa Cruz province, Argentina). In this work we compare, and discuss, zooarchaeological variability in assemblages from early hunter-gatherer groups present during the Pleistocene-Holocene transition – ca. 12.000 and ca. 7500 years BP – in the basin. The bone materials studied here came from two stratigraphic contexts: the first was AEP-1 at Piedra Museo, located in the lower basin, and the other was from Cueva Maripe in the La Primavera area, located in the upper sector of the basin. The comparison between the assemblages was undertaken using 30 taxonomic, anatomic and taphonomic variables that were present in a standardized from across both assemblages. The results obtained demonstrate the existence of different historical trajectories in both sectors and a differential use of fauna resources by the prehistoric communities that inhabited these areas.

Paleoenvironments revealed by rare-earth element systematics in vertebrate bioapatite from the Lower Devonian of Svalbard

In situ rare-earth element (REE) compositions have been measured in early vertebrate microremains from the Lower Devonian basin of Andrée Land (Svalbard), with the aim of obtaining information about their early depositional environment and potential reworking. Vertebrate microremains with different histology were used for the analyses, sourced from two different localities of marginal marine to freshwater sediments from geographically distant parts of the Grey Hœk Formation (Skamdalen and Tavlefjellet members). We selected thelodont and undescribed ?chondrichthyan scales, which allowed us to define potential taxonomic, histological, and taphonomic variables of the REE uptake. Results showed REE concentrations to be relatively uniform within the scales of each taxon, but apparent discrepancies were visible between the studied localities and separate taxa. The compilation of REE abundance patterns as well as REE ratios have revealed that thelodont and ?chondrichthyan originating from the same locality must have had different burial and early diagenetic histories. The shapes of the REE profiles, together with the presence and absence of the Eu and Ce anomalies, equally suggested different depositional and diagenetic environments for these two sympatric taxa resulting from either stratigraphical or long-distance reworking. The REE concentrations appear to have visible differences between separate dental tissues, particularly between enameloid and dentine of thelodonts, emphasizing the importance of in situ measurements in microfossil biomineral geochemistry.

Nuevos Datos para las Inhumaciones en Urnas de Sitios Arqueológicos Guaraníes del Extremo Meridional de la Cuenca del Plata

Many urn burials were recorded among the complex mortuary behaviors observed in archaeological sites belonging tothe Guarani archaeological unit. Urn burial analyses are generally scarce and, particularly, in the southern point of La Plata basin. The objective of this work is to contribute to the Guarani society’s knowledge by the analysis of human remains buried in urns from archaeological sites located in the Parana Delta (Argentina). This region is the southern point of this Amazonian group’s expansion, whose mortuary remains are well preserved, in contrast to other Guarani´s regions. In this work, we analyze the human skeletal remains recovered from urn burials from three archaeological sites located in the Parana Delta: Arroyo Malo, Arroyo Fredes y Arroyo La Glorieta. These sites were excavated at the beginning of the 20th century by many researchers and today are part of Museo de La Plata´s collections. We studied sexual composition, age and anatomical structure as well as a set of taphonomic variables. The results show the preponderance of male adult individuals, represented mainly by long bones and cranial elements, some of them with cut marks and red paint (ochre) in abundant quantities. These indicators, along with others of taphonomical origin, indicate the secondary treatment of the dead product of the disassembly, defleshing and selection of certain anatomical units.

Tafonomía y tecnología lítica en un ambiente altamente dinámico: El caso de la pinguinera del islote La Pastosa (Pcia. de Río Negro) Patagonia, Argentina [Taphonomy and lithic technology in a highly dynamic environment

Taphonomy and lithic technology in a highly dynamic environment: The case of the penguin colony of La Pastosa Islet (Rio Negro Province), Patagonia, Argentina This paper presents the first results of taphonomic and technological analyses of the lithic assemblage recovered on La Pastosa Islet, on the coast of Rio Negro province, Patagonia, Argentina. This archaeological record is particular because it has been under a high formational dynamic and is located in an area recently occupied by a colony of Magellan penguins ( Spheniscus magellanicus ). Two samplings of lithic material were made, for which technological, metric and taphonomic variables were registered. La Pastosa is an 8 hectare islet, which is located 768 m. from the continent, and is only attached to it at low tide by a narrow land strip that runs through a marsh. While the absolute age of this island is unknown, we know that from the late Holocene, around 3000 BP, sea level reached current levels (Favier Dubois 2013), and since that time the islet was visited by hunter-gatherers, who buried their dead in the highest part of the island (Favier Dubois et al. 2007, Favier Dubois et al. 2009). Today, this area has a great biodiversity, such as a reproductive colony of sea lions ( Otaria flavescens ) which has recently formed (Svendsen et al. 2009: 8) as well as a variety of seabirds. Artifact sampling was focused on the area of greatest density of lithic artifacts, currently close to the center of the islet (Figure 1). The context of recovery of these materials can be divided into three categories: A) common transit areas of penguins that give shape to paths free of vegetation; B) burrow entrances C) marginal spaces that correspond to sectors of debris accumulation (twigs and dry grass, feathers, Penguin carcasses) on the margins of the transit area (Figure 2). During sampling, the original position of the artifacts, or face of recovery, and context of discovery were recorded. At the lab, general typological (tool, core, or debitage), raw materials, metrics (volume in mm3), and taphonomic variables were registered. The latter in particular were used to characterize and compare both assemblages. The recording and analysis of artifact modification due to taphonomic processes is a line of research to approach the intensity of the physical transformations in the archaeological context, and to indicate their degree of integrity (Schiffer 1983; Burroni et al. 2002). The variables recorded were as follows, the level of weathering in each tool face (W: W0, W1, W2, W3); the presence of carbonate concretion; and the integrity of the piece (whole or broken). The results show that intensive penguin traffic and burrow activity exposed buried materials in certain sectors (Figure 5.1), which are pushed through paths with no vegetation (Figure 5.2) and redeposited in “fall off” areas with little or no circulation (Figure 5.3). These are mostly small patches of vegetation and organic waste, which have high relative stability. For this reason we believe that in these patches, materials are more likely to accumulate and perhaps re-enter into the substrate. Preliminary evidence obtained for this study area suggests that the lithic record is in continuous formation, in this case because of the action of penguins. Since the establishment of this colony is recent, its impact on the archaeological record is significant.

Colecciones antiguas, datos nuevos: Primeros resultados del análisis de las colecciones bioarqueológicas del Humedal del Paraná Inferior

Durante fines del siglo XIX y principios del siglo XX tuvieron lugar varias exploraciones y excavaciones en sitios arqueológicos del humedal del Paraná inferior, originando en consecuencia un gran acervo de materiales bioarqueológicos, entre otros, depositados hoy en día en el Museo de la Plata de la Universidad Nacional de La Plata y en el Museo Etnográfico de la Universidad de Buenos Aires. Si bien algunos de los resultados derivados de aquellos trabajos de campo fueron publicados, otros permanecen inéditos. El objetivo de este trabajo es dar a conocer algunas características de dichas colecciones bioarqueológicas a través del análisis de 252 individuos que las conforman. En este sentido, procedimos a la determinación sexual y estimación etaria de la muestra y al registro de variables tafonómicas, este último con el fin de poder identificar el posible contexto de inhumación de donde provienen dichos individuos. A partir de este análisis y siguiendo los datos publicados se discriminaron entre inhumaciones en contacto directo con la tierra o en urnas. A su vez, se dio cuenta de una segmentación espacial en base a categorías de sexo y edad para algunos sitios, como así también de la presencia de adornos personales de metal, ocre y marcas de corte en algunos huesos. De esta manera, esperamos resaltar el valor que tienen las colecciones de museos como así también contribuir y ampliar nuestro conocimiento sobre las características de las poblaciones prehispánicas de la región.