New insights about the construction and use of shell mounds from the geochemical analysis of mollusks: an example from the greater San Francisco Bay

A new method developed by Schweikhardt et al. (2011) for the geochemical analysis of bay mussels is applicable (when combined with radiocarbon assessments) for examining the seasonal construction patterns and growth cycles of coastal mound sites over time. Ideally suited for the analysis of mollusk fragments in museum collections, this method allows archaeologists to evaluate divergent models about the functions of mound sites, as well as the mobility practices and social organizations of the mound builders. In this case study, the method is employed to examine two adjacent mounds (Ellis Landing, Brooks Island) in the San Francisco Bay Area, California to assess whether their occupants may have participated in a broader multi-site community dating to the Late Period (1100–250 BP).     

Geochemical methods for inferring seasonal occupation of an estuarine shellmound: a case study from San Francisco Bay

Seasonal patterns of Native American residence and use of shell mounds of the San Francisco Bay area, California are of great interest. This work investigates seasonal occupation by means of a new method for interpretation of geochemical data from Mytilus trossulus specimens recovered from one of these structures, the Ellis Landing Shell Mound (CA-CCO-295). The approach, which is suitable for relatively small shell fragments from a variety of archaeological contexts, is used to infer the environmental conditions (temperature and salinity of ambient water) at harvest time, compared with average conditions for the period, and thus estimate the season during which the shells were harvested. This information, in turn, is employed to evaluate current models about the growth and construction of prehistoric shell mounds in San Francisco Bay. The method was applied to seven different lenses in the shell mound ranging in age from ∼240 cal yr BP to ∼3510 cal yr BP. We found that, although seasonal occupation varied over time, it generally was confined to summer through late fall, with little indication of winter gathering. Our findings suggest that California shell mounds, such as Ellis Landing, were constructed in a very different manner than some other mounded places used by contemporaneous hunter-gatherers elsewhere in North America.     

Pre-pottery farmers on the Pacific coast of southern Mexico

Large island-like shell mounds along the southern coast of Mexico are the earliest known archaeological sites on the Pacific margin of Mesoamerica. These aceramic deposits date to between 7500 and 3800 cal BP and have been interpreted as locations where foragers, living elsewhere seasonally on the coastal plain, harvested shellfish and other estuarine resources. Based on an accumulation of paleoecological data from elsewhere in the lowland Neotropics of Mesoamerica, southern Central America and South America we pose and provide a first test of an alternative subsistence model: that the Archaic Period populations in this area were slash and burn farmers. Burned maize phytoliths first appear in these sedimentary records at 6500 cal BP in association with macroscopic charcoal and forest disturbance plant taxa. Periodic burning and forest disturbance, consistent with farming activities, are also evident in the macroscopic charcoal record between 6500 and 4700 cal BP. Pollen, phytolith and charcoal records all point to sustained burning, forest disturbance and the cultivation of maize between 4700 and 3800 cal BP. These data suggest that people were slash and burn farming during the Archaic Period prior to the adoption of pottery and the proliferation of Early Formative Period villages and full-fledged agriculture based on near or total reliance on crop plants after ∼3800 cal BP.     

Pottery firing temperatures: a new method for determining the firing temperature of ceramics and burnt clay

A new method for determining the maximum firing temperature of ceramics and burnt clay is presented. The technique relies on measuring the magnetic susceptibility on a step-wise re-fired sample. The validity of the method has been tested by determining firing temperatures of two sets of clay samples fired at temperatures ranging from 400 to 1000 °C. Aliquots of the same samples have been studied petrographically by optical microscopy on thin sections and analyzed by powder X-ray diffraction in order to monitor structural and mineralogical changes as a function of temperature. The method is demonstrated on samples from four geographically widely different sites and it is applied to a larger set of ceramics of Late (ca. AD 900–AD 1450) and Inca (ca. AD 1480–AD 1532) periods from the Northwestern Argentine region, dating to a limited period of time prior to the fall of the Inca Empire. The method is shown to be a powerful tool in revealing archaeological information about the change in firing technologies in the pre-Hispanic societies in the Andean area through time.     

Mussels and mongongo nuts: logistical visits to the Cape west coast,South Africa

Very large late Holocene shell middens (‘megamiddens’, some over 10 000 m³ in extent) along a 20 km section of the west coast of South Africa provide a particular interpretative challenge in determining whether they result from residential visits or from logistical processing of shellfish for transport and consumption elsewhere. The latter interpretation is preferred here and is consistent with stable carbon isotopic readings on coastal human burials and site contents that illustrate that groups visited specific localities, collected and dried black mussels and then transported and consumed the dried product inland. The sizes and contents of these large middens contrasts sharply with those of unquestionably residential residues from earlier and later time periods. This approach is supported with reference to the ethnographically described processing and consumption of mongongo nuts by 20th century San of the Kalahari.     

Reconstructing Middle Horizon mobility patterns on the coast of Peru through strontium isotope analysis

The pre-Columbian coastal site of Ancón, Peru frequently has been interpreted as an important outpost of the highland Wari Empire, inhabited by individuals from the sierra and the coast. In order to test this hypothesis, bone–tooth pairs from 35 Middle Horizon (550 AD–1000 AD) Ancón skeletons were analyzed for strontium isotopes, which vary by geologic provenance. Results indicate that 34 of the 35 individuals have ⁸⁷Sr/⁸⁶Sr enamel and bone values higher than Ancón's biologically available strontium isotope range. Nitrogen and carbon isotope data from a subset of the Ancón skeletons suggest that the higher than expected ⁸⁷Sr/⁸⁶Sr values among the Ancón sample likely reflects a diet rich in marine resources rather than migratory activity, and highlight the need to use multiple lines of evidence to track residence change at sites where individuals relied on resources other than locally grown terrestrial foods. The one remaining individual, a young female of elite status, has an enamel strontium isotope signature much lower than the available data for local fauna and soil indicating that she was not raised locally. Her enamel ⁸⁷Sr/⁸⁶Sr ratio fits well within the range of strontium isotope values established for the inland Wari site of Conchopata [Tung, T.A., Knudson, K.J. Social identities and geographical origins of Wari trophy heads from Conchopata, Peru. Current Anthropology, in press.], and suggests that highland, Wari immigrants may have been present at Ancón during the Middle Horizon.     

Insights into immigration and social class at Machu Picchu,Peru based on oxygen,strontium, and lead isotopic analysis

The Inca Empire (AD 1438–1532) made common practice of relocating individuals, households and entire communities throughout their expansive realm for different reasons depending on subjects' assigned social class. Reconstructing patterns of immigration at Inca-period sites could therefore permit some estimation of the social class(es) among their constituents, and thereby provide insights into the functional dynamics of Inca political economy. However, this is a difficult endeavor using only archaeological lines of evidence. This study presents oxygen, strontium and lead isotopic results from the well-preserved, well-contextualized skeletal population (N = 74) from the Inca site of Machu Picchu, Peru. Isotopic data are used to reconstruct patterns of immigration at the site, which are in turn used to directly estimate the social class of the population. The resulting isotopic data are widely distributed with no apparent modality, matching the expected distribution of a particular class of nonelite retainers. A novel application of multivariate statistics coupled with geological and faunal isotopic reference data also permits tentative estimation of individuals' regions of origin. This study provides empirical and analytical frameworks for future research in reconstructing residential movement and class dynamics in the late prehistoric Andes.     

Incipient aquaculture in prehistoric California?: Long-term productivity and sustainability vs. immediate returns for the harvest of marine invertebrates

California archaeologists have proposed two alternative methods for harvesting mussels—“stripping” and “plucking”. These two methods are modeled and compared with experimental data from central California (Jones, T.L., Richman, J.R., 1995. On Mussels: Mytilus californianus as a Prehistoric Resource, North American Archaeologist 16, 33–58) and archaeological data from the Punta Gorda Rockshelter, a well-stratified coastal shell midden in northern California. Foragers at the Punta Gorda Rockshelter appear to have practiced a “stripping” technique at approximately 24 month intervals. It is argued that, while this strategy reduced immediate foraging returns, it increased the long-term net productivity of the mussel beds.     

Reconstructing prehistoric hunter–gatherer foraging radii: a case study from California's southern Sierra Nevada

The concept of the foraging radius is essential to understanding hunter–gatherer settlement, subsistence, and sociocultural complexity yet is notoriously difficult to reconstruct archaeologically. Late prehistoric Western Mono foraging radii in the southern Sierra Nevada were reconstructed using GIS analysis of least-cost path distances between dispersed caching features and centralized residential features. Mean distances from settlements to caches exhibit a bimodal distribution, with peaks between 0.5 and 5.0 km, and 6.0 and 8.5 km, the former representing a caching limit and the latter a foraging limit around major settlements. Combined, these data demarcate a two-part foraging radius predicated not only on sustaining winter group aggregations but also on facilitating spring and summer residential moves. These results show the efficacy of using features and simple GIS-based spatial analyses to reconstruct prehistoric foraging radii and provide the means to model the energetics of different foraging behaviors, these speaking strongly to the social and economic factors conditioning the development of complex hunter–gatherer societies.     

The use of strontium isotopes as an indicator of migration in human and pig Lapita populations in the Bismarck Archipelago,Papua New Guinea

This paper examines the potential use of strontium isotopes (⁸⁷Sr/⁸⁶Sr) for identifying migration within Lapita populations and their commensal animals, specifically the pig (Sus scrofa). Lapita people (ca. 3300–2200 BP) were the initial colonists of the island groups to the east of the Solomon Islands, spreading from Papua New Guinea to Tonga and Samoa within a few centuries. Mobility is assumed to have been an important mechanism for maintaining cultural solidarity between Lapita communities. It has been previously argued that Lapita populations became progressively more sedentary over time after the initial colonising events. Two Lapita sites, Kamgot and Balbalankin, from the Anir Islands in the Bismarck Archipelago are included in the analysis and fall within the Early (ca. 3300–3000/2900 BP) and Middle (ca. 3000/2900–2700 BP) Lapita periods respectively.     

Shellfish Exploitation in the Western Canary Islands Over the Last Two Millennia

ABSTRACT

The residents of the Canary Archipelago consumed limpets since the arrival of humans ～2500 yrs. ago, and these harvested gastropods were deposited in large coastal shell middens. This work preliminarily explores shell margin oxygen isotope composition (δ¹⁸O) and body size of the black limpet (Patella candei d’Orbigny, 1840) from archaeological sites in the Canary Islands to assess possible seasonal variability and intensity of shellfish collection throughout the late Holocene. The shell margin δ¹⁸O values of 100 shells (radiocarbon dated between ～500 and ～1800 cal. yr BP) were analysed to estimate sea surface temperature (SST) at time of death. Paleotemperature estimates suggest shellfish harvesting was not year-round, and was avoided in the cooler months (when SST?<?20°C). This pattern differs from most higher latitude Mesolithic and Neolithic human groups, which gathered shellfish year-round, targeting winter more heavily. Preliminary body-size measurements suggest shell sizes have experienced a decline from aboriginal times to the present, which possibly resulted from increasing anthropogenic pressures. During aboriginal inhabitation, maximum adult shell size remained stable, suggesting that present-day harvesting practices are more intense than harvesting from aboriginal human groups. This intensive collection has likely diminished the average adult size of limpet populations in the islands by ～27%.     

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.     

Boat-based foraging and discontinuous prehistoric red abalone exploitation along the California coast

Temporally and spatially discontinuous pulses of heavy prehistoric exploitation of red abalone (Haliotis rufescens) have been documented along the southern and central California coast. This article examines the very late (post-950 cal BP) appearance of numerous red abalone processing sites on the Monterey Peninsula in central California. We test three prominent explanations offered for the sudden onset of red abalone processing sites: trophic cascades resulting from human predation on sea otters, logistical foraging by inland residents, and changes in sea surface temperature. A trophic cascade appears to have occurred but does not fully explain the nature or timing of the phenomenon in the region.     

Investigating shellfish deposition and landscape history at the Natia Beach site,Fiji

The relationship between environmental variation and subsistence practices is a central point of discussion in much Oceanic archaeology. While human predation can significantly reduce prey populations, environmental variation also contributes to reductions in prey abundance, possibly leading to increased human competition and resource scarcity. At the Natia Beach site, Nacula Island, Fiji, geoarchaeological evidence suggests that coastal progradation began soon after initial occupation of the coastal plain. Additionally, at approximately 650 BP a marked increase in clay and silt deposition occurred. Changes in coastal geomorphology may be explained by landscape response to regional Mid-Holocene sea level fall combined with human induced soil erosion due to upland settlement. Smaller scale environmental changes associated with climate variability may have also played a role. Additionally, landscape change appears to have had a measurable impact on local nearshore mollusks that are sensitive to high levels of water turbidity. Minor evidence of human exploitation is observable in this shellfish assemblage, although changes in predation pressure may have allowed shellfish populations to recover. Increased ceramic diversity and fortified settlements also appear at approximately 650 BP on Nacula and other parts of Fiji. The suite of changes at Natia may be explained by processes of regional and local environmental changes, and human adaptation in terms of subsistence, spatial organization, and competition.     

Paleodiet in northern Chile through the Holocene: extremely heavy δN values in dental calculus suggest a guano-derived signature?

Dental calculus extracted from the teeth of 28 prehistoric human skeletons from coastal and valley archaeological sites in northern Chile that date from the Archaic period (∼2300 BC) to the Late Intermediate period (AD 1476) was analyzed for stable isotope (δ¹⁵N, δ¹³C) compositions. δ¹⁵N compositions were extremely heavy (+17.8 to +33.1‰), but comparable to some studies using conventional human biomaterials (hair, nail, muscle) at other prehistoric sites in northern Chile. There was a negative correlation between δ¹⁵N and δ¹³C for coastal sites, but a positive correlation for valley sites. Results for the valley sites point to a diet that was influenced by marine resources throughout all time periods. The unusually heavy δ¹⁵N values for the coastal sites require a dietary component with a δ¹⁵N composition significantly heavier than that of marine resources. The hyper-aridity at the study area (mean annual rainfall of 0.5–0.6 mm/year) is a likely contributing factor to the production of heavy δ¹⁵N values, but is unlikely to account for the heaviest δ¹⁵N values (>+30‰). One possible explanation for the heaviest δ¹⁵N values is that dietary components were impacted by isotopically-heavy guano, which is abundant in the region. Guano may have been used as a fertilizer during crop cultivation at the onset of the Formative period, continuing through the Historic period after Spanish contact. The indirect impact of guano from abundant bird habitats in the region may have influenced wild foodstuffs harvested throughout the pre-agricultural period. Results provide support for the utility of dental calculus as a proxy for obtaining stable carbon and nitrogen isotope signatures for use in paleodietary studies.     

Insights into early Holocene hunter-gatherer mobility on the Peruvian Southern Coast from mollusk gathering seasonality

Quebrada de los Burros (QLB) is an early Archaic coastal archaeological site in southern Peru (∼18.1°S) and the most extensively studied in the area for this period. It was occupied from 10 to 6.5 ka by fishermen also practicing hunting and mollusk gathering. Shell growth lines in 116 individuals of the surf clam Mesodesma donacium were studied to determine the month of their death (±2 months). Our results show that, for the whole occupation period, mollusk gathering was a seasonal activity mainly practiced during austral spring and summer. A change occurred between the early and the middle Holocene: the mollusk gathering season in the middle Holocene occurred ∼3 months earlier in the year than in the older levels. This behavior change could have a cultural origin, rather than dictated by the environment for it is associated with changes in the lithic industry. QLB occupants also hunted herbivores in the nearby lomas ecosystems. These plant communities only grow during the fog season from June to December, suggesting that the site was occupied during this season. A comparison of the span of the mollusk gathering season and the lomas season suggests that, at least during the early Holocene, QLB was occupied all the year round. A permanent freshwater source and the proximity of the sea, the lomas, and raw lithic materials, provided ideal conditions for a permanent occupation. This result reveals a strategy based on a seasonal alternation between marine and terrestrial resources exploitation.     

Probing dietary change of the Kwädąy Dän Ts'ìnchį individual,an ancient glacier body from British Columbia: II. Deconvoluting whole skin and bone collagen δC values via carbon isotope analysis of individual amino acids

The remains of the Kwäd?y Dän Ts'ìnch? individual, a frozen male human, were recovered from a retreating glacier within the Tatshenshini-Alsek Park in British Columbia in August 1999. In order to provide information on both the geographical origin of this individual and low long he spent in the remote interior region prior to his death, molecular analysis and compound-specific carbon isotope analyses were performed on individual amino acids purified from his skin and bone. Gas chromatographic quantification of constituent amino acids of both tissues revealed a molecular distribution characteristic of collagen, dominated by glycine and to a lesser extent proline, hydroxyproline and alanine. Chiral gas chromatography indicated that protein preservation in both tissues was exceptional. Carbon isotope analysis of a faunal assemblage from an earlier prehistoric site from southern British Columbia provided reference dietary amino acid δ¹³C values for terrestrial (deer and domestic dog) and marine species (salmon and sealion), showing clear separation in all amino acids, particularly glycine which was extremely ¹³C-enriched in the marine animals. The distinction between terrestrial and marine organisms was increased by exploring Δ¹³C_{Glycine-Phenylalanine} values (6.6 ± 0.6‰ and 15.0 ± 2.1‰, respectively), which were higher in the latter by approximately 8‰, mirroring the increased δ¹⁵N_{Bulk collagen} values observed for the marine animals (R² = 0.78; p < 0.001). The Kwäd?y Dän Ts'ìnch? individual's bone had a similarly elevated Δ¹³C_{Glycine-Phenylalanine} value of 15.6 ± 1.0‰, indicating his extreme reliance on marine dietary resources throughout early life. The skin amino acid δ¹³C values were consistently lower than those observed for bone, with a concurrently lower Δ¹³C_{Glycine-Phenylalanine} value of 12.7 ± 0.9‰. The shift between the carbon isotope composition of bone (long-term diet) and skin amino acids (short-term diet) confirmed a sudden divergence away from marine food sources in the last months of life, consistent with his discovery 80 km inland.     

A Bayesian AMS C chronology of the Classic Maya Center of Uxbenká, Belize

Archaeologists require precise chronologies of cultural change to understand the nature and timing, and causes and effects, of ecological and social transformations. The Uxbenká Archaeological Project (UAP) has made chronology building a main goal, employing epigraphic data, artifact seriation, and high-precision AMS ¹⁴C dating. With more than 60 ¹⁴C dates with measurement errors below ±25 ¹⁴C yr, primarily on single charcoal specimens, Uxbenká may be the most intensively dated Classic Period site in the tropical Maya Lowlands. Here we take the next step, combining this rich chronometric dataset with associated stratigraphic information in OxCal's Bayesian framework to generate a high-resolution chronology of Uxbenká's early development and expansion in southern Belize. We show how archaeologists may take advantage of complex architectural stratigraphy to constrain broad calibrated ranges during the Classic Period, and to estimate dates for observed construction events that can not be directly dated (e.g., clearing/leveling plazas, laying plaster floors, renovating/rebuilding structural elements). Our analysis confirms the antiquity of the ceremonial Stela Plaza (Group A), where first construction is estimated between 60 cal BC and cal AD 220 and is associated with a Pre-Classic structure obscured by later construction and reorientation of the group to a N-S alignment ca. AD 150–310. The analysis also indicates initial leveling and construction at plaza Group B from cal AD 60–310 and Group D from cal AD 20–240, both earlier than previously assumed. Though Late Classic contexts are not as well represented by direct dates, architectural modifications are documented at all three plaza groups after AD 550, including the extensive plastering, laying paving stones, and construction of facades on existing structures. The resulting chronology revises our previous thinking on the mode of settlement and development of Classic Maya society at Uxbenká and indicates specific areas of investigation to elucidate events in the Late and Terminal Classic at the site, including political and social fragmentation and the abandonment of the urban core late in the Classic Period.     

Human impacts on ancient shellfish: a 10,000 year record from San Miguel Island,California

We use measurements of more than 11,000 marine shells from 41 archaeological components to construct a 10,000 year record of human impacts on ancient mussel and abalone stocks on San Miguel Island, California. General reductions in the mean size of mussel and abalone shells gathered through time are attributed to growing human population and predation pressure. Based on comparison with historically documented changes in shellfish communities caused by the local extinction of sea otters in the 19th century, changes in mean shell size and the abundance of other shellfish species may have been facilitated by Native American predation on sea otters as early as 7500 years ago. Despite having measurable impacts on local ecosystems, Native Americans on San Miguel harvested huge quantities of shellfish throughout the Holocene. Such long-term harvests appear to have been sustained by an early emphasis on fishing at lower trophic levels, by periodically shifting village locations, and by intensifying the use of finfish and sea mammals through time. This pattern of “fishing up the food web” contrasts with many modern fisheries, suggesting that the study of ancient fisheries can help us better manage our own endangered coastal ecosystems.     

A late Holocene pollen record from Lake Almalou in NW Iran: evidence for changing land-use in relation to some historical events during the last 3700 years

A pollen diagram was prepared from Lake Almalou, a volcanic crater wetland located on the eastern flanks of the Sahand Volcanic Complex in NW Iran. The core provides a 3700-year record of human activity and environmental change in an upland region. We attempt to relate vegetation changes to both climatic change and historical events. Variations of anthropogenic pollen indicators suggest several phases of intensified human activities. Two strongly expressed agricultural phases are dated at about 2450–2220 cal BP (Achaemenid Empire) and 230–30 cal BP (collapse of Safavid Dynasty to the modern period). Historical rather than climatic events appear to be the main controlling factors for upland land-use dynamics. Fruticulture has been practiced in the region at least since the Iron Age, reaching its maximum importance 1500–1250 cal BP during the reign of Sassanid Empire; it declined by the time of Islamic conquest of Iran (651 AD). The Little Ice Age is tangibly recorded by higher lake water levels most probably due to both lower summer temperatures and higher annual precipitations. Low values of cereal-type and cultivated tree pollen during this period may indicate a change in the lifestyle from the cultivation of fields and orchards to a more nomadic life dominated by summer pasture. The modern period (1850 AD onwards) is characterized by expansion of agricultural activities to upland areas and intensified pastoralism.