Shellfish, Seasonality, and Sedentism: δ18O Analysis of California Mussels from Early Holocene Shell Middens on San Miguel Island, California (original) (raw)
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Abstract To evaluate coastal settlement and land use strategies among maritime hunter-gatherers, we analyzed oxygen isotope (δ18O) data from 131 marine carbonate samples from 21 California mussel (Mytilus californianus) shells obtained from a large ∼8,200-year-old shell midden (CA-SRI-666) on California’s Santa Rosa Island. Seasonal distributions of the isotopic data were assigned using a paleo-sea surface temperature model created by comparing modern sea surface temperatures (SST) to a fully profiled ∼8,200-year-old shell. For 20 additional shells, we used two sampling strategies to compare season-of-harvest inferences and explore whether the Early Holocene site occupants were sedentary. Estimated season-of-harvest differed by 35 % between the two sampling methods, corroborating recent isotope analysis of an 8,800- year-old shell midden on San Miguel Island. Shellfish appear to have been collected year-round at CA-SRI-666 from intertidal or subtidal water temperatures similar to modern SST in the vicinity of eastern Santa Rosa Island. The isotope results are consistent with other evidence from CA-SRI-666 that suggest that the site served as a residential base for relatively sedentary maritime people.
Analyzing stable isotopes in mollusk shells allows archaeologists to address issues ranging from seasonality of harvest, to settlement and subsistence strategies, sea surface temperatures, and nearshore paleoecology. Studying California mussel shells from an ∼8,800-year-old shell midden on San Miguel Island, we investigate how mollusk growth rates influence sampling strategies for determining seasonality. Using a fully profiled shell as a standard to interpret more limited measurements (terminal growth band plus one) on 39 additional shells, we identified what appeared to be a multi-seasonal occupation. Sampling 20 of the 39 shells more intensively, however, changed our conclusions about season of harvest for 35 percent of the analyzed shells, producing data more consistent with other evidence for a short-term occupation of CA-SMI-693. Sampling strategies for determining seasonality from marine
Seasonal stability in Late Holocene shellfish harvesting on the central California coast
2008
Oxygen isotope determinations from 92 California mussel (Mytilus californianus) shells from ten archaeological sites in central coastal California show relatively stable seasonal harvesting patterns between 3600 CAL BP and historic contact (AD 1769). Coastal occupants harvested mussels nearly yearround and seem to have occupied individual residential bases throughout the seasonal cycle. Interior groups returned with mussels from the coast mostly in the spring and early summer, but almost never in the late summer/early fall when nut crops were harvested. These findings suggest two interdependent groups with distinct seasonal settlement strategies: inland people, reliant on acorns and other nut crops harvested in the fall, and coastal inhabitants who were less involved with acorns. This pattern is sup ported by accounts recorded by the first Spanish explorers in AD 1769. While some interior groups may have been seasonally migrating ''collectors,'' coastal populations were less mobile, inhabiting individual residential sites throughout the year, albeit not necessarily on a permanent basis. These findings high light the strong influence of coastal environments and resources on hunter-gatherer mobility.
Journal of Archaeological Science, 2013
Seasonality estimates based on stable isotope analyses of shellfish remains has been an important thrust of settlement pattern reconstruction, allowing researchers to place people on the landscape at points in space at different times of the year. In exposed coastal settings seasonality reconstructions are typically dependent on annual changes in water temperature. This paper has two goals. First, we continue development of a method for determining shellfish harvest seasonality in estuarine environments where annual salinity changes, not temperature, drive isotopic variation. Second, we contribute to settlement pattern studies by showing how small and large sites can be linked into a single system by examining different site types and shellfish species. Our case study focuses on the Late Prehistoric period of the San Francisco Peninsula, includes a large shellmound (CA-SMA-6) and an ephemeral camp (CA-SFR-171), and examines clam (Macoma spp.) and mussel (Mytilus spp.) harvesting. In this case, data support a fission-fusion settlement pattern, with periods of dispersal during late winter through early summer and aggregation in late summer through early winter.
Journal of Ethnobiology, 2016
Shells are a visible component of archaeological middens in Central California. While coastal and bay shore sites are often dominated by shells, these food items were sometimes hauled many kilometers from their collection points and are found in appreciable numbers in inland sites as well. Using oxygen and carbon stable isotope data from 44 Mytilus sp. (mussel) shells, we reconstruct shellfish seasonality harvesting at one inland site dating to the Middle Period (ca. 2500-1000 cal yrs BP), CA-SOL-364. Data show that shells were collected from nearby Suisun Marsh and were harvested almost exclusively during winter, a pattern that contrasts with coastal and bay shore sites. Such a harvesting signature is unlike that expected for a food staple or a feasting resource. We suggest mussels were harvested as a fallback food, as a source of protein or micronutrient to complement carbohydrate-rich foods that were stored and consumed during winter, or perhaps were only exploited as opportunity costs relaxed during winter, making sessile mussels an attractive subsistence pursuit.
Central Place Foraging and Shellfish Processing on California's Northern Channel Islands
We use a central place forager model for shellfish processing to understand Middle Holocene (7550-3600 cal BP) human settlement patterns on California’s northern Channel Islands. This period was associated with increasing sedentism and special purpose sites. We examine the processing and transport costs of two high-ranked shellfish species collected during the Middle Holocene, red abalone (Haliotis rufescens) and California mussel (Mytilus californianus), and how these costs influence archaeological assemblages at coastal and interior settlements. Experimental data and the biology of these species suggest that red abalones are less likely than mussels to be transported long distances (~2 km) without field processing. Consistent with these expectations, coastal red abalone midden sites (CA-SRI-109 and -338) are dominated by large red abalone shells and California mussels are most abundant at contemporaneous inland sites (e.g., CA-SRI-50). Large coastal settlement sites (CA-SRI-5, -19, -116, and -821) had the highest overall shellfish diversity. A stable oxygen isotope study suggests that special purpose sites were occupied seasonally and large coastal settlements were more likely to be inhabited year-round. Our study suggests that transportation and processing costs of food resources were important variables in the development of early hunter-gatherer settlement patterns.
Maritime Subsistence at a 9300 Year Old Shell Midden on Santa Rosa Island, California
Journal of Field Archaeology, 1999
A deeply buried shell midden (CA -SRI-6) on Santa Rosa Island) Califtrnia appears to have been a residential campsite occupied about 9300 years ago. Although few artifacts were recoveredfrom this Early Holocene component) faunal remains suggest a heavy reliance on marine resources)probably supplemented by terrestrial plant foods. Dietary reconstructions suggest that shellfish (especially abalone) provided about 85% of the estimated meat yields) fish about 14%) with birds and sea mammals each contributing less than 1 %. These data suggest that Early Holocene adaptations on the Channel Islands were distinct from the coastal mainland in many ways and that maritime hunter-gatherers had adapted to a variety of Pacific Coast habitats by this early time.
Institutionalized differences in social status developed on California’s northern Channel Islands from the Late Middle (A.D. 650-1150) to Late (A.D. 1300-1782) periods. This is associated with the proliferation of sedentary communities along the coasts of these islands and a number of important socioeco- nomic changes, including a greater emphasis on fishing and the production of non-food craft items. These changes were particularly rapid during the Middle to Late Period Transition (MLT; A.D. 1150-1300) and partly attributed to significant environmental change during this interval. Population-resource imbalances caused by decreased marine productivity, drought, or some combination of the two have been suggested as possible environmental triggers for the sociopolitical changes evident in the archaeological record at this time. Shell midden deposits at CA-SRI-15 provide a unique opportunity to test whether elevated sea surface temperature (SST) reduced marine productivity during the MLT and contributed to these population resource imbalances. This is because the site was occupied relatively continuously from the Late Middle Period through the Late Period. Faunal records and associated oxygen isotopic data from the site do not support the hypothesis that increased SST reduced marine productivity during the MLT.
Shellfish, Geophytes, and Sedentism on Early Holocene Santa Rosa Island, Alta California, USA
The Journal of Island and Coastal Archaeology, 2019
Archaeobotanical remains recovered from a large ~8000-year-old shell midden (CA-SRI-666) on Santa Rosa Island provide the first ancient plant data from this large island, shedding light on ancient patterns of plant use, subsistence, and sedentism. Faunal data from shell midden samples retrieved from three site loci contain evidence for harvesting of rocky intertidal shellfish and estuarine clams and oysters from a paleo-estuary in the vicinity. CA-SRI-666 appears to have been an Early Holocene village site occupied year round. A key to the development of early sedentary societies on the island may have been geophytes, especially Brodiaea-type corms, which provided an abundant source of carbohydrates and calories that complemented marine resources rich in fat and whole animal proteins. Our data demonstrate the value of integrating paleobotanical and zooarchaeological data from island and coastal archaeological sites to help elucidate human social, cultural, and environmental dynamics, including sedentism.
The late Holocene archaeofaunal record of the San Francisco Bay Area demonstrates temporal declines in the abundance of low-cost, high-ranked marine and terrestrial resources. During later periods of occupation, faunal assemblages are often dominated by lower-ranked, higher-cost resources, suggesting an increase in diet breadth through time. Archaeological resource intensification models argue that this marks a late Holocene decline in foraging efficiency in the Bay Area, driven by human-induced harvest pressure. This study examines dietary change in the region using stable carbon and nitrogen isotope data from 65 human burials, spanning two temporal components (cal AD 55e890 and cal AD 762e1550) at the Ellis Landing site (CA-CCO-295). The strong linear relationship between collagen carbon and nitrogen isotope values reflects both marine and terrestrial food consumption, with individuals showing a high level of dietary variability at the site. No temporal trend or meaningful sex differences were found in isotope values. The widening of diet breadth predicted by the archaeofaunal record occurred prior to the occupation of the Ellis Landing shellmound site. The trend in exploiting a greater amount of terrestrial resources during the Middle and Late Period in central California was supported by isotopic evidence.