Morphometric and taphonomic analysis of granular ark (Anadara granosa) dominated shell deposits of Blue Mud Bay,northern Australia

Metrical analyses of complete mollusc shells have commonly been used to examine aspects of prehistoric mollusc demography, and by extension to investigate potential human exploitation of a variety of species. Recently it has been highlighted that several taphonomic processes, such as fragmentation, have the potential to introduce size bias into these archaeological samples, particularly towards smaller size classes, and thus the potential to significantly skew results of these metrical analyses. This is investigated here by deriving morphometric equations for the sand/mudflat bivalve Anadara granosa, a species prevalent in archaeological sites across northern Australia. A linear regression model based on a series of valve measurements, resulting in high coefficients of determination, demonstrates strong predictive power for size reconstruction. The effects of fragmentation on assemblages from two case study sites are then examined as a means of reviewing issues of differential size preservation, variation in mean valve size, and evaluating the strength of previous interpretations of intensive human exploitation in Blue Mud Bay. Based on these analyses it appears that A. granosa mean size is not significantly affected by fragmentation as other species described in the literature, and previous interpretations retain their validity.     

Shell Morphologies of Bay Scallops,Argopecten irradians,from Extant and Prehistoric Populations from the Florida Gulf Coast: Implications for the Biology of Past and Present Metapopulations

Genetically conservative changes in a bivalve population may be mirrored by morphological changes in the shells of individuals in that population. The rate of such evolutionary change is usually so slow that the changes in shell morphology cannot be detected in short-term studies of local populations. When selective pressure becomes severe, however, the magnitude of the genetic changes may be intensified, and thus the magnitude of the morphological changes in the shells may be greater—and more detectable. We compared the morphometric features of specimens from archaeological sites with those from geographically coherent modern collections to determine if such detectable morphological changes have taken place in the populations studied. Analyses of bay scallop shells (Argopecten irradians) from nine modern populations spanning Florida's entire Gulf coast and from four archaeological sites located from central to southern Florida reveal that major morphological shifts in the shells of two local populations have occurred sometime in the past 500 to 1500 years. These shifts may have implications regarding the persistence of the scallop metapopulations and the efficacy of future efforts to conserve the species.     

Wild or domesticated? An ancient DNA approach to canid species identification in South Africa's Western Cape Province

The fragmentary remains typical of archaeological fauna can prove impossible to identify when confronted with closely related sympatric species. In southern Africa domesticated dogs (Canis familiaris) and black-backed jackals (Canis mesomelas) pose just such a problem, rendering difficult an accurate assessment of the timing of arrival of domesticated dogs in the region. Contextual evidence has suggested that canid remains from four Later Stone Age archaeological sites were likely to be domesticated dogs rather than jackals, and were subjected to ancient DNA analyses to determine species. Every tested specimen proved to derive from black-backed jackals. These data provide not only an unexpected window on southern African prehistory, but also highlight the value in applying ancient DNA techniques to archaeological species identification.     

Oxygen isotopic composition of limpet shells from the Beagle Channel: implications for seasonal studies in shell middens of Tierra del Fuego

Shell middens distributed along the coastal areas of the Beagle Channel (Tierra del Fuego) testify the primary role of marine resources in the successful social dynamic of hunter–gatherer–fisher societies (HGF) in extreme high latitude environmental conditions. Intertidal and subtidal limpet species are frequently identified taxa of these archaeological deposits. We investigated whether shell δ¹⁸O of the limpet species Nacella deaurata is a valuable record of local sea surface temperature (SST) and ambient water δ¹⁸O (δ¹⁸Ow) fluctuations, and in turn can be used to estimate the season of its exploitation by Holocene HGF. Sequential shell δ¹⁸O of modern species track seasonal changes of SST and δ¹⁸Ow. The comparison of shell δ¹⁸O profiles of N. deaurata and Nacella magellanica (a coexisting species) suggests the occurrence of distinct growth rate and physiological adaptations between species. Shell δ¹⁸O of zooarchaeological specimens of N. deaurata from Lanashuaia II suggests that animals were exploited predominantly in winter and that experienced similar environmental conditions of present day at ∼1320 years BP. Results also indicate that N. deaurata is a valuable candidate for studying past seasonal changes in SST and δ¹⁸Ow in this southernmost part of South America.     

Prehistoric shell beads on the Georgia coast

ABSTRACT

The prehistoric peoples living along the Georgia coast fabricated and used shell beads for millennia. Out of a number of mollusk species inhabiting the region, only a few were selected for the fabrication of beads. The knobbed whelk (Busycon carica) was the most common species used, and it represents the most common whelk found in Atlantic coastal waters. The lightning whelk (Busycon sinistrum), the second most common whelk in the region, was occasionally used in the production of beads. Small numbers of beads were made from marginella and olive shells and, rarely, from bivalve species. Small beads were manufactured from the body whorl of whelks, while larger beads were fabricated from whelk collumella. Shell beads appear in small quantities in Late Archaic period contexts, and then almost disappear during the Woodland period. Beads reappear in quantities at about AD 800 in the Early Mississippian period. More shell beads have been recovered from Mississippian period archaeological contexts along the northern Georgia coast than along the southern coast, reflective of cultural differences between these two geographic areas in the post-Woodland period era.     

Oxygen isotope seasonality in a temperate estuarine shell midden: a case study from CA-ALA-17 on the San Francisco Bay,California

Seasonality determination using stable oxygen isotope (δ¹⁸O) analyses in archaeological mollusk shell has been largely limited to aquatic settings where one of the two factors that control shell δ¹⁸O – water δ¹⁸O (or salinity) and temperature – is assumed to be constant. Open coastal marine environments reflect the former situation, and tropical estuaries constitute the latter. In an effort to expand stable isotope seasonality to an ecological setting where neither variable remains constant, we present a model of annual shell δ¹⁸O cycle of aragonite deposition derived from instrumental data on salinity and temperature from San Francisco Bay, California. The predicted range of modeled shell δ¹⁸O is consistent with observed δ¹⁸O values in prehistoric and modern shells when local conditions are considered. Measurements of δ¹⁸O taken at 0 mm and 2 mm from the terminal growth margin were made on 36 archaeological specimens of Macoma nasuta from a late Holocene hunter-gatherer site CA-ALA-17, and season of collection was inferred using the shell δ¹⁸O model. We conclude that shellfish exploitation occurred through the year with the exception of fall, which may indicate scheduling conflicts with acorn harvesting or other seasonally abundant resources elsewhere. The model supports the feasibility of stable isotope seasonality studies in temperate estuaries, provided that instrumental records are available to quantify the relevant water conditions at appropriate spatial and temporal scales.     

Provenance analysis of Olivella biplicata shell beads from the California and Oregon Coast by stable isotope fingerprinting

While Olivella beads are a common component of archaeological sites in California, and were widely traded in prehistory, no method has been developed to trace individual beads to a point of origin. This study examines the potential of stable carbon and oxygen isotopes to source Olivella beads from the Pacific coast. The study shows that 1) the oxygen isotopic composition of modern Olivella biplicata shells faithfully varies with ambient sea surface temperature and local upwelling, lending themselves to sourcing studies; 2) oxygen isotope ratios in modern shells can be used to identify shells that grow north versus south of Point Conception, California; and 3) shell carbon isotope ratios may further subdivide these two regions into more spatially restricted source zones. Analyses on a small sample of 10 beads found at various archaeological sites within the interior of California suggest that all were made in southern California.     

Stability in the South Pacific surface marine C reservoir over the last 750 years. Evidence from American Samoa, the southern Cook Islands and the Marquesas

Although minor climatic and sea-level changes have been documented for the South Pacific during the late Holocene, our understanding of the consequent impact of these changes on the marine ¹⁴C reservoir, and therefore the ¹⁴C content of shellfish, is limited. Ultimately, this has implications for documenting the chronology of human movement and adaptation in this region. In this paper we compare marine reservoir (ΔR) data obtained from tightly controlled archaeological proveniences with known-age, pre-AD 1950 shells from the southern Cook Islands, American Samoa, and Marquesas Islands. Results indicate that there has been no significant change in the near-shore marine reservoir in these three locations over the last ca. 750 years. Furthermore, known-age, pre-AD 1950 shell samples provide more precise ΔR values for use in sample calibration than archaeological paired shell/charcoal samples. This is attributed in part to the limitations of assigning provenance and age to material from archaeological sites. On the basis of these results we conclude that the known-age, pre-AD 1950 shell derived ΔR values can be used to calibrate shell ¹⁴C results from deposits of late Holocene age.     

First dendroarchaeological dates of prehistoric contexts in South America: chullpas in the Central Andes

Despite the existence of long-lived tree species with excellent tree-ring characteristics, the use of dendrochronological techniques for dating archaeological contexts has been very limited in South America. Recent research in the Bolivian Altiplano of the Central Andes has yielded a network of Polylepis tarapacana chronologies that goes back to the 13th century. This species was regularly used by local populations since pre-Columbian times as raw material for beams, lintels, hooks and other architectural features in houses, storage chambers, and sepulchers. The aim of this study is to argue in favor of the potential of P. tarapacana for providing high resolution dates of significant archaeological events during the pre-Columbian era. The chronology of chullpas (burial towers and storage chambers) in the southern Andean Altiplano is used as a case study. Growth rings from P. tarapacana have provided several centennial-length dendrochronological records including a reference regional chronology covering the last 786 years in the Central Andean highlands. Based on this long reference chronology calendar years were assigned to woody pieces from pre-Hispanic chullpas. Dendroarchaeological results are consistent with contextual evidence and most radiocarbon dates from woody samples and related archaeological items. Our results indicate that P. tarapacana has a high potential for providing annually-resolved tree-ring dates for archaeological contexts in the Altiplano since the early 13th century.     

Morphometric analysis of limpets from an Iron-Age shell midden found in northwest Portugal

The present work reports an analysis of a shell midden found in Terroso hillfort, an important Iron-Age oppidum located in northwest Portugal. The midden was dated from the latest phase of occupation of the hillfort, between the Ist century BC and the Ist century AD (Roman period), and contained 684 well-preserved Patella shells. The identification of archaeological shells was carried out comparing them with modern specimens collected in two shores in the neighborhood of the hillfort. The identification of modern shells was based on radula pluricuspid teeth and shell morphology. Relative abundance of Patella species in the Terroso midden was different from modern populations. Archaeological shells were dominated by Patella vulgata, but Patella intermedia was the most abundant species in modern populations. Dimensions of archaeological shells were very different from modern populations. Shell length range and variability in archaeological shells were lower than in the modern populations. Log height vs. length plots for archaeological shells were different from modern populations. Patella shells from Terroso midden was significantly taller then modern specimens. These differences between archaeological shells and modern populations could be due to environmental changes, namely an increase in wave action and intensity. These harsher costal conditions could have resulted from an alteration in the morphology of the coast, caused by a rise in the mean sea level from 2000 years BP to the present. Alternatively or additionally, the observed differences can be related to gathering strategies. Archaeological shells could have been selected by size, and collected preferentially at high shore and in sheltered sites.     

10,000 years of human predation and size changes in the owl limpet (Lottia gigantea) on San Miguel Island,California

To investigate potential human impacts on California Channel Island shellfish stocks over the past 10,000 years, we measured 1718 owl limpet shells from 19 archaeological components on San Miguel Island. Inhabiting the middle intertidal zone of Pacific Coast rocky shores, owl limpets are slow-growing mollusks that can live for 30 years and reach lengths of over 100 mm. Recent ecological studies indicate that owl limpets are highly susceptible to heavy human predation, which results in reduced mean shell sizes among Lottia populations along the coasts of Alta and Baja California. On San Miguel Island, we identified a significant trans-Holocene reduction in mean owl limpet size, beginning more than 6500 years ago and accelerating at least 4400 years ago. Fluctuations in limpet size show no clear correlation with changes in sea surface temperature and marine productivity, suggesting that increased predation by growing human populations was primarily responsible for the reduction in Lottia size over time. Our results provide further evidence that prehistoric peoples significantly influenced nearshore fisheries long before the development of the commercial and industrialized fisheries of historic times.     

Inter-site variability in the season of shellfish collection on the central coast of British Columbia

High-resolution stable oxygen isotope analysis of the bivalve Saxidomus gigantea from shell midden sites was applied to identify seasonal patterns of resource procurement on the central coast of British Columbia, Canada. A total of 90 archaeological shells were examined from eight distinct sites spanning a 4500-year period. Combining micro-growth pattern analysis with high-resolution stable oxygen isotope sampling allows for a precise season of collection to be determined in estuarine bivalves recovered from archaeological sites. The results of the stable oxygen isotope analysis provide insights into seasonally structured harvest of S. gigantea (butter clam), which is associated with different types of sites. The results show a variety of patterns, including multi-seasonal collection, intensive seasonal harvesting and casual, supplemental use of butter clams at different locations.     

Changes in shell gathering in an early agricultural society at the head of Ise Bay,Japan

We examined changes in shell gathering in an early agricultural society at the head of Ise Bay, Japan based on the analysis of almost 20,000 individual shell remains from four coastal settlements. We analyzed historical changes in the composition and size range of the shell species Meretrix lusoria. The most common species went from Crassostrea gigas in the early Middle Yayoi period (about 400–350BC) to M. lusoria in the mid-Middle Yayoi period (about 320–200BC). It is possible that the seacoast tideland, an environment suitable for C. gigas, was buried in sediment from the rivers and thereby transformed into muddy sand bottoms, an environment more suitable for M. lusoria. We also analyzed historical changes in the size range of M. lusoria. The mean size of M. lusoria increased significantly from the early Final Jomon (about 1250–1000BC) to the late Early Yayoi (about 500–400BC), from the late Early Yayoi to the early Middle Yayoi, and from the early to the mid-Middle Yayoi periods. Evidence suggests that during the Yayoi period, the demand for shells decreased and therefore, the pressure to collect M. lusoria also decreased. We concluded that the larger specimens of M. lusoria were collected selectively.     

Morphometric Analysis of the Yellow Clam (Amarilladesma Mactroides) to Interpret Fragmentary Archaeological Specimens

Mollusks were an important component in the diet of the hunter-gatherer groups that inhabited the coastal zones of South America during the Holocene, as recorded in the littoral shell and archaeological sites distributed from Brazil to Argentina. Although the shells are relatively resistant to physical and chemical agents, they are also fragile and various post-depositional processes affect their integrity. Puente de Fierro is an archaeological site located in the south of Buenos Aires province (Argentina), in which remains of the yellow clam (Amarilladesma mactroides) were recovered totally fragmented. We investigate if a morphometric model based on modern clams could be applied to estimate shell size and individual biomass of archaeological clams. Linear regression models reveal a high correlation between the chondrophore length and the shell length, and therefore, the individual biomass of the yellow clam.     

A conceptual model for freshwater mussel (family: Unionidae) remain preservation in zooarchaeological assemblages

Expectations for survival of vertebrate remains have been well developed and intensely studied in the zooarchaeological taphonomic literature. Taphonomic studies of shellfish remains focus on marine species and on variables relevant to remains from paleontological contexts (e.g., fossil marine beds). In this paper we develop a conceptual framework from which to derive expectations concerning the preservation of freshwater mussel remains focusing on two parameters, shell microstructure and shell shape. Shell size does not influence survivorship. Our model is validated through application to late Holocene zooarchaeological mussel assemblages from north Texas. Taphonomically robust species are important regarding zooarchaeological and biogeographic interpretations based on mussel paleofaunas, and fragile species are important indicators of whether or not an assemblage is well preserved.     

Species specific marine radiocarbon reservoir effect: a comparison of ΔR values between Patella vulgata (limpet) shell carbonate and Gadus morhua (Atlantic cod) bone collagen

A number of recent studies of the UK coastal environment have assessed the ¹⁴C marine radiocarbon reservoir effect (MRE) via quantification of ΔR values for several periods throughout the Holocene using marine mollusc shells. However, none have employed fish bone as the marine sample, and the importance of being able to use this material as a reliable dating tool is evident when considering the boom in the British fish trade during the first millennium AD, the so-called ‘fish event horizon’, and the corresponding volume of fish remains that appear in the archaeological record from this time. This study compares ΔR values derived using the multiple paired sample approach employing burnt cereal grain (Hordeum sp.) as the terrestrial sample and either fish bone [North Sea cod (Gadus morhua)] or marine shell [limpet (Patella vulgata)] as the marine sample. The results show a general trend of increasing ΔR for the fish bone compared to shell, however, the differences are not statistically significant when the standard error for predicted values is used as the measure of variability in the ΔR values.     

Mineral weathering in forest soils and its relevance to the preservation of the buried archaeological resource

There is more woodland in Britain now than for many centuries and considering many international climate change mitigation policies, woodland cover, both in Britain and internationally, is being promoted. However, neither the management of existing woodlands nor their expansion should be at the expense of important archaeological evidence. Due to the large number of known archaeological sites, the large areas of land with uninvestigated archaeological potential and the expanding woodland cover, suitable mitigation strategies need to be developed to allow preservation in situ of important sites. An understanding of how woodland soils and the buried archaeological resource interact is, therefore, essential. This paper utilises ongoing environmental research into the mineral weathering rates in forest soils and considers its application to artefact preservation. The study concludes that soil water pH, its movement, and the saturation of dissolved ions in the soil solution are major factors determining both mineral and artefact longevity. A simple guide to artefact longevity based on these properties is proposed and a geochemical model for predicting loss is tested. These tools could be applied to any soil or individual horizon irrespective of land-use.     

Experimental micromorphology in Tierra del Fuego (Argentina): building a reference collection for the study of shell middens in cold climates

Commonly used in archaeological contexts, micromorphology did not see a parallel advance in the field of experimental archaeology. Drawing from early work conducted in the 1990’s on ethnohistoric sites in the Beagle Channel, we analyze a set of 25 thin sections taken from control features and experimental tests. The control features include animal pathways and environmental contexts (beach samples, forest litter, soils from the proximities of archaeological sites), while the experimental samples comprise anthropic structures, such as hearths, and valves of Mytilus edulis (the most important component of shell middens in the region) heated from 200 °C to 800 °C. Their micromorphological study constitutes a modern analogue to assist archaeologists studying site formation and ethnographical settings in cold climates, with particular emphasis on shell midden contexts.     

Analytical examination of animal remains from Borneo: the painting of bone and shell

Examination of a selection of shell and bone from archaeological assemblages excavated at Niah Cave and Gua Sireh, both of which are located in Sarawak, Borneo, has revealed the deliberate application of coloured material to one or more surfaces. Small fragments of the surface colourant were analysed using a variety of techniques, including microscopy, energy dispersive microwave analysis and infra-red spectrophotometry. These procedures established that, although red in colour, the applied coating in each instance was not red iron oxide. It is suggested that, based on the chemical components present, this coating was a tree resin or a similar organic substance. The paper further reports the presence of enhanced chloride values in the colourant recovered from the ancient human cranial fragment tested. It is suggested that elevated concentrations of this trace element may indicate that the site, the human remains or ingredients within the colourant were once in close proximity to the sea.     

Red abalone collecting and marine water temperature during the Middle Holocene occupation of Santa Cruz Island,California

Oxygen isotope values derived from prehistoric mussel (Mytilus californianus) shell calcite are used to determine whether sea-surface temperatures in the vicinity of the Punta Arena site (CA-SCRI-109) on Santa Cruz Island, California, were cooler than present between 6300 and 5300 cal BP. This site and others in the western sector of the island dating to this period are distinctive because of the presence of large red abalone (Haliotis rufescens) shells, a species that historically has been subtidal around Santa Cruz and the other northern Channel Islands. Comparison of temperature values derived from archaeological shells with those from modern mussel shells, along with water temperatures derived from satellites, indicates that waters were cooler during the 6300 to 5300 cal BP period. These results are consistent with a previous study and support the interpretation that collection of red abalone during the 6300–5300 cal BP period was partly the result of cooler water temperatures that made this large mollusk more available to foragers in the intertidal or shallow subtidal zone.