Declines in Mammalian Foraging Efficiency during the Late Holocene, San Francisco Bay, California

Resource intensification models that have been posited for prehistoric California predict decreases in foraging efficiency during the late Holocene, Using implications of the fine-grained prey model of optimal foraging theory, I derive an index of the efficiency of vertebrate prey choice from the relative abundances of large- and small-sized prey items. I then test the intensification models with late Holocene mammalian faunas from San Francisco Bay shellmounds. Dramatic linear decreases in the relalive frequency of artiodactyls compared to the smaller sea otters (Enhydra lutris) throughout the occupational histories of particular localities strongly support the resource intensification models. The declines in artiodactyl abundances are not correlated with late Holocene climatic indices developed for this region, with changes in the seasonal use of shellmounds, or with technological innovations. An intra- and interregionally consistent pattern in declining abundances of large mammals in environmentally distinct regions throughout California suggests that resource depression driven by human predators may be the single most important cause of the declines. These patterns have far-reaching implications concerning the long-term human role in structuring prehistoric ecosystems.     

Avian resource depression or intertaxonomic variation in bone density? A test with San Francisco Bay avifaunas

Previous analyses of the Emeryville Shellmound fauna suggested that ever-expanding late Holocene human populations of the San Francisco Bay area depressed a wide range of vertebrate taxa, including cormorants (Phalacrocorax), geese (Anserinae), and large shorebirds (e.g., Numenius, Limosa). Far-reaching implications for prehistoric human behavior, historical ecology, and modern conservation biology have resulted from that work. We test the generality of the bird-based conclusions here by documenting temporal trends in avifaunal abundances from five additional sites located on the San Francisco Peninsula. Analyses of these data reveal patterns identical to those found at Emeryville, showing significant declines through time in the relative abundances of both geese and cormorants between about 2000 and 700 B.P. New photon absorptiometric-based density data for cormorants, geese, and ducks (Anatinae) are used to determine if the declines through time in the relative abundances of geese and cormorants are correlated with variation in the extent of density-mediated attrition observed in these faunas. The data and analyses presented here suggest that while density-mediated attrition played a role in structuring element abundances in these avifaunas, there is no evidence that it varied systematically through time to produce the revealed patterns in taxonomic abundances. Resource depression thus remains a viable hypothesis for the declining abundances of large-sized waterbirds during the late Holocene of the San Francisco Bay region. The new bone density data we present should be useful to analyses of archaeological and paleontological avifaunas wherever these or related taxa are found around the world.     

On Behavioral Depression in White-tailed Deer

Behavioral depression is a decline in prey availability because of enhanced alert response, movement away from areas, increased social behavior, and other responses to predators. This form of resource depression is an alternative hypothesis to be contrasted to over-exploitation that potentially explains a decrease in hunting efficiency over time should the zooarchaeologist observe a decline in the relative abundance of remains of high-rank prey. Gregarious ungulates, such as many North American cervids, may exhibit such behavioral responses under predation. The white-tailed deer (Odocoileus virginianus), one of the most common high-rank prey animals from Holocene archaeological sites in eastern North America, is less gregarious, more r-selected, and exhibits greater home-range fidelity than other cervids. As a result, whitetails are less likely to exhibit behavioral depression than other North American ungulates, which may explain their common occurrence in Holocene archaeological faunas, such as that from the Eagle??s Ridge site in southeast Texas where resource depression appears to have occurred from 4,500 to 1,500?years ago. The behavioral ecology of ungulate species should be considered on a case-by-case basis to develop testable hypotheses about prehistoric human predation.     

Agent-Based Simulation of Holocene Monsoon Precipitation Patterns and Hunter-Gatherer Population Dynamics in Semi-arid Environments

Based on archaeological evidence from Kutch-Saurashtra (N Gujarat, NW India), we use agent-based modelling (ABM) to explore the persistence of hunter-gatherer (HG) groups in semi-arid environments in the mid and late Holocene. Agents interact within a realistic semi-arid environment dominated by the monsoon. Precipitation trends are modelled from instrumental records (1871–2008) calibrated with existing models for the Asian monsoon in the Holocene (c. 12 ka–present). Experiments aim at exploring dependencies between population dynamics and climate-driven environmental change (in terms of resource availability) for precipitation patterns at the local, regional and continental scales. Resources are distributed across a simplified ground model. Average yearly precipitation (AYP, i.e. mean) and variance in yearly precipitation (VYP, i.e. standard deviation) are the main parameters affecting resource availability in the simulations. We assess the effects of environmental change on HG populations at different timescales: (1) patterns of seasonal (inter-annual) resource availability, (2) effects of changes in mean precipitation trends over the long (Pleistocene–Holocene) and the mid (Holocene, millennial) periods, and (3) effects of intra-annual precipitation variability, i.e. changes in standard deviation from mean precipitation trends over the short period (annual to decadal). Simulations show that (1) strong seasonality is coherent with the persistence of HG populations in India, independently of the geographical scale of the precipitation models, (2) changes in AYP over the mid period (Holocene) are not sufficient to explain the disappearance of HG populations in Kutch-Saurashtra (K-S) 4 ka and (3) precipitation variability (VYP) over the short period (annual to decadal) is the main parameter affecting population performance and overall ecosystem dynamics. To date, sufficiently refined palaeoclimatic records do not exist for the study area, but higher VYP values 4 ka do not exclude the possibility that other factors may have driven the disappearance of HG populations in Kutch-Saurashtra.     

Paleodietary analysis of a San Francisco Bay Area shellmound: stable carbon and nitrogen isotope analysis of late Holocene humans from the Ellis Landing site (CA-CCO-295)

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 55–890 and cal AD 762–1550) 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.     

Prehistoric behavioral depression of cormorant (Phalacrocorax spp.) on the northern California coast

Resource depression is often assumed to result from the over-exploitation of a prey species leading to declines in its population, and therefore availability, to human hunters. However, two other forms of resource depression are noted in the ecological literature: behavioral and micro-habitat depression. Data presented in this paper demonstrate resource depression of cormorants (Phalacrocorax spp.), a coastally breeding and semi-pelagic bird genus, at a coastal site in northern California. Citing modern cormorant behavior and a lack of evidence for intensive rookery exploitation, it is argued that the observed resource depression resulted from changes in cormorant behavior that decreased encounter rates for human hunters. Such behavioral depression is cited as a buffer to the extirpation of prey in mainland settings.     

A Test of Ideal Free Distribution Predictions Using Targeted Survey and Excavation on California’s Northern Channel Islands

Using targeted survey, excavation, and radiocarbon dating, we assess the extent to which human settlement patterns on California’s northern Channel Islands fit predictions arising from the ideal free distribution (IFD): (1) people first established and expanded permanent settlements in the regions ranked high for environmental resource suitability; (2) as population grew, they settled in progressively lower ranked habitats; and (3) changes in the archaeological record associated with high population levels such as increases in faunal diversity and evenness in high-ranked habitats are coincident with the expansion to other areas. On Santa Rosa Island, the early permanent settlements were located in both high- and middle-ranked locations, with the most extensive settlement at the highest ranked locations and only isolated sites elsewhere. Settlement at a low-ranked habitat was confined to the late Holocene (after 3600 cal BP). Drought influenced the relative rank of different locations, which is an example of climate adding a temporal dimension to the model that episodically stimulated population movement and habitat abandonment. Because the IFD includes a wide range of cultural and environmental variables, it has the potential to be a central model for guiding archaeological analysis and targeted field research.     

Explaining prehistoric variation in the abundance of large prey: A zooarchaeological analysis of deer and rabbit hunting along the Pecho Coast of Central California

Three main hypotheses are commonly employed to explain diachronic variation in the relative abundance of remains of large terrestrial herbivores: (1) large prey populations decline as a function of anthropogenic overexploitation; (2) large prey tends to increase as a result of increasing social payoffs; and (3) proportions of large terrestrial prey are dependent on stochastic fluctuations in climate. This paper tests predictions derived from these three hypotheses through a zooarchaeological analysis of eleven temporal components from three sites on central California’s Pecho Coast. Specifically, we examine the trade-offs between hunting rabbits (Sylvilagus spp.) and deer (Odocoileus hemionus) using models derived from human behavioral ecology. The results show that foragers exploited a robust population of deer throughout most of the Holocene, only doing otherwise during periods associated with climatic trends unfavorable to larger herbivores. The most recent component (Late Prehistoric/Contact era) shows modest evidence of localized resource depression and perhaps greater social benefits from hunting larger prey; we suggest that these final changes resulted from the introduction of bow and arrow technology. Overall, results suggest that along central California’s Pecho Coast, density independent factors described as climatically-mediated prey choice best predict changes in the relative abundance of large terrestrial herbivores through the Holocene.     

Focused,intense and long-term: evidence for granular ark (Anadara granosa) exploitation from late Holocene shell mounds of Blue Mud Bay,northern Australia

Explanatory frameworks relating to the appearance of shell mounds and the exploitation of molluscs (particularly the sand/mudflat bivalve Anadara granosa) during the late Holocene have tended to emphasise stasis and continuity. Very few analyses have adequately investigated the intensity of human predation during the mound period and the potential effects on the particular prey species. To this end, the biological and ecological characteristics of A. granosa, the dominant molluscan species for much of the known period of occupation in the region, are considered in detail, in combination with assessing the potential for human impact through predation via the measurement of 9106 A. granosa valves from three shell mounds. In explaining long-term economic change in this region of northern Australia, the focus has been placed on the analysis of relative changes and trends through time in prehistoric resource exploitation.     

An experimental approach to the study of interpersonal violence in Northeastern Patagonia (Argentina), during the late Holocene

This paper incorporates an experimental approach to the study of violence patterns in Northeastern Patagonia (Argentina) during the late Holocene. The underlying hypothesis considers a close association between socio-ecologic alterations during the Medieval Climatic Anomaly (MCA) (ca. 1150-600 years BP; Stine, 1994, 2000) and a probable increase in conflict levels. In order to test this hypothesis, human skulls (n = 986) were analyzed for bone lesions, discriminating late bone lesions, such as those produced by metal tools. The experimental approach used swine (Sus scrofa domestica) skulls, as proxies for human skulls, and incorporated original sabers. From this discriminating analysis, it can be inferred that no significant increase in violence signs were recorded until the first stages of Hispanic-indigenous contact (first half of 17th century). These findings emphasize the need for a revision of the implications of the dynamics of human populations in Northeastern Patagonia during the late Holocene.     

Isotope sourcing of prehistoric willow and tule textiles recovered from western Great Basin rock shelters and caves – proof of concept

Isotope and trace-metal analyses were used to determine the origin of plants used to manufacture prehistoric textiles (basketry and matting) from archaeological sites in the western Great Basin. Research focused on strontium (⁸⁷Sr/⁸⁶Sr) and oxygen (¹⁸O/¹⁶O) isotope ratios of willow (Salix sp.) and tule (Schoenoplectus sp.), the dominant raw materials in Great Basin textiles. The oxygen-isotope data indicated that the willow and tule used to produce the textiles were harvested from the banks of rivers or in marshes characterized by flowing water and not from lakes or sinks. The strontium-isotope data were useful in showing which plants came from the Humboldt River and which came from rivers headed in the Sierra Nevada.     

A new ornamented artefact from Poland: final palaeolithic symbolism from an environmental perspective

An ornamented artefact made of antler, found in the environs of ?widwin (Pomerania, NW Poland), was subject to structural and environmental analysis. Radiocarbon dating (10?700 ± 60 BP or 10?910–10?680 cal. BC) places it in the Final Palaeolithic, at the end of Weichselian (boundary of the Allerød and Younger Dryas). The surface of the artefact bears a complex ornament of zigzag lines and an anthropomorphic drawing, representing most probably a woman with spread legs. Palynological analysis of the deposit in which the object was found indicates forest communities (pine-birch forests) with some open areas, in a cool climate. Ultrastructural examination points to the elk Alces alces (Linnaeus, 1758) as the source species; the antler was at the stage of intense growth which indicates that the elk was killed or died in the spring-summer period. The antler was large, and the object made of it was used for a long time, playing a role in rituals and symbolic culture of a hunting group. The ornamentation shows an affinity to the early Mesolithic art and makes it possible to better trace the relations between the hunters of the late Pleistocene and those of the early Holocene.     

Stable isotope evidence for dietary and cultural change over the Holocene at the Sabana de Bogotá region,Northern South America

The Sabana de Bogotá in the northern Andes is an interesting region to investigate temporal patterns of dietary variation because it counts with a vast archeological and osteological record for the last 10,000 years. In this paper, stable isotope data of human archeological bone collagen and apatite were used to study the evolution of diet and major subsistence transformations taking place during the Holocene (～9000–600 cal BP). Paleoenvironmental reconstructions and the isotopic ecology of the Sabana de Bogotá were used as an interpretative baseline. Stable isotope measurements (δ¹³C_col, δ¹³C_ap, δ¹⁵N, and Δ¹³C_col-ap) representing hunter-gatherers, horticulturalists, and agriculturalists (N = 134 individuals) were analyzed by using bivariate, regressional, and discriminant statistical techniques. Results show that early Holocene hunter-gatherers (9000–7000 cal BP) consumed mostly C₃ vegetal resources locally available. In contrast, animal protein was less important. Middle Holocene hunter-gatherers (6000–4500 cal BP) continued with the food foraging pattern observed in the earlier counterparts and presented a slight increase in C₃ animal protein intake. During the initial late Holocene ca. 4000 cal BP, important shifts in subsistence strategies occurred when populations presented a trend toward mixed C₃/C₄ diets, and by ca. 3500 cal BP, there is a clear signal of C₄ crops (i.e., maize) consumption concomitant with the introduction of ceramic technology. During the final late Holocene (last 2000 cal years BP), intensive agriculture was adopted and humans presented relatively diverse diets integrated by C₄ and C₃ crops, C₃-C₄ feeding animals, and freshwater resources. Such dietary change coincides with an increase in sociopolitical complexity, population size, and a general decline in health.     

Historical ecology of late Holocene sea otters (Enhydra lutris) from northern British Columbia: isotopic and zooarchaeological perspectives

We examined the isotopic composition (δ¹³C and δ¹⁵N) of sea otter (Enhydra lutris) bone collagen from ten late Holocene (ca. 5200 years BP–AD 1900) archaeological sites in northern British Columbia (BC), Canada. Because sea otters are now extinct from much of this region and have not fully recolonized their former range (e.g. Haida Gwaii and most of northern BC) these data represent an important first step towards better understanding sea otter foraging ecology in BC. The isotopic data suggest a diet composed primarily of benthic invertebrates, with a very low reliance on epibenthic fish. There is very low isotopic and thus inter-individual dietary variability in Holocene BC sea otters during the late Holocene. Furthermore, zooarchaeological abundance data suggest that otters represented a widespread and significant focus of aboriginal hunting practices on the northern BC coast during the mid- to late-Holocene. The consistent reliance on a small number of low-trophic level prey and limited dietary variability in Holocene BC sea otters may reflect top-down impacts on otter populations by aboriginal peoples. As part of our assessment of sea otter diet, we review trophic discrimination factors (Δ¹³C and Δ¹⁵N) for bone collagen from published literature and find marked variability, with mean values of +3.7 ± 1.6 for Δ¹³C (n = 21) and +3.6 ± 1.3 for Δ¹⁵N (n = 15).     

Prehistoric seal carcass exploitation at the Shag Mouth site,New Zealand

Seal populations in New Zealand declined dramatically during the prehistoric period. The loss of this important resource significantly affected the foraging practices at the Shag River Mouth site. Previous research documented substantial changes to the diet with the decline of seals and the corresponding decline in foraging efficiency. In this study, I examine how New Zealand foragers altered their use of seal carcasses as the availability of these marine mammals declined. Otariid seal data from the Shag River Mouth site in southern New Zealand are analyzed to test changes in butchery/transport and skeletal element breakage patterns expected with resource depression and declining foraging efficiency. This research shows that at Shag Mouth, seal carcasses were used more intensively over time. However, bone breakage patterns showed little change in the exploitation of within-bone nutrients.     

The Broad Spectrum Revolution at 40: Resource diversity,intensification, and an alternative to optimal foraging explanations

More than 40 years ago Kent Flannery coined the term Broad Spectrum Revolution (BSR) in reference to a broadening of the subsistence base of Late Pleistocene hunter–gatherers in the Near East that preceded and helped pave the way for the domestication and plants and animals and the emergence of agriculture. Set within a demographic density model that projected differential rates of population growth and emigration in different resource zones of the Near East, Flannery’s BSR quickly became a global construct linking resource diversification and intensification to imbalances between population and environmental carrying capacity. In recent years the BSR has proven especially attractive to researchers working within an optimal foraging theory (OFT) framework in which diversification and intensification of subsistence only occurs within the context of resource depression, caused by either demographic pressure or environmental deterioration. This OFT perspective, that situates human societies in a one-way adaptive framework as they are forced to adapt to declining availability of optimal resources, however, is increasingly being called into question. Numerous examples of diversification and intensification are being documented in contexts of resource abundance shaped, in part, by deliberate human efforts at ecosystem engineering intended to promote resource productivity. An alternative approach, framed within a newer paradigm from evolutionary biology, niche construction theory (NCT), provides a more powerful explanatory framework for the BSR wherever it occurred.     

Holocene Relative Sea-Level Change on the Isle of Skye,Inner Hebrides,Scotland

Holocene relative sea-level (RSL) changes are described for the Isle of Skye, based upon evidence from isolation basins and back barrier environments. RSL rose across low-lying coastal areas in the early Holocene, inundating isolation basins in the Sleat peninsula, and then fell back in the early-middle Holocene before a fluctuating rise occurred later in the middle and late Holocene. A short-lived marine inundation at one site may have been caused by an episode of rapid RSL rise after the discharge of Lakes Agassiz–Ojibway in North America and/or the Holocene Storegga Slide tsunami, generated by submarine landsliding off South-West Norway. The empirical evidence for RSL change on Skye is compared with a recent shoreline-based glacio-isostatic adjustment model, which includes Skye, showing altitudes for the Holocene Storegga Slide tsunami, Main Postglacial, Blairdrummond and Wigtown shorelines in the area. The empirical evidence is shown to be in accord with the altitudes predicted by the model.     

Ancient Iberian horses: a method to recover DNA from archaeological samples buried under sub-optimal conditions for preservation

Existing methods to extract, amplify, and sequence ancient DNA (aDNA) from horse bone and teeth were optimized to recover DNA from a depositional environment of highly permeable acidic soil. DNA was successfully retrieved using 0.10g of bone powder from horse (Equus sp.) remains dating to 25 K years utilizing the methods optimized for this archaeological material. The genetic analyses were performed in a facility that is dedicated to ancient DNA research (Paleo-DNA Laboratory, Thunder Bay, ON, Canada) and has not been previously used to analyse modern or ancient horse DNA. Research was replicated to obtain reliable sequencing results for six samples from the Iberian Peninsula that were consistent with published sequences of Equus caballus. The archaeological sequence data obtained support hypotheses that promote the significance that the Iberian Peninsula has had to the multi-focal centres of origin for horse domestication and distribution of modern horse breeds. The data presented may provide evidence of the existence of an Iberian refugium for Equus during the last glacial period, 10 K years BP. Further molecular data analyses will enhance the ideas presented by this data and our understanding of horse domestication and phylogeny. The optimization of molecular techniques to successfully obtain DNA using minimally destructive, cosmetically sensitive techniques from archaeological remains endeavours to foster further cooperation between museums and researchers.     

Intensification revisited: assessing resource specialization at Crystal River (8CI1) and Roberts Island (8CI41), Florida

ABSTRACT

Archaeologists typically associate resource intensification with population expansion, environmental change, and political strategizing. Many Late Woodland and Mississippian societies of the Southeast eschewed dietary diversity in favor of harvesting fewer types of resources that could meet the subsistence demands of incipient aggregation. Foods such as maize and shellfish can provide humans with predictable caloric yields and are amenable to control by individuals or corporate groups. However, some archaeologists have identified scenarios in which small-scale societies intensified resources in the absence of population growth and social inequality. Ritual economies can periodically place high demands on the materials used for gatherings and ceremonies. These events then may leave material residues of economic intensification, which archaeologists might easily mistake as evidence for population expansion or social evolution. We use diversity and equitability estimates of zooarchaeological deposits from Crystal River (8CI1) and Roberts Island (8CI41), Florida, to demonstrate that some Woodland period societies periodically intensified their use of resources amidst population decline and heightened ritual activity. We suggest that the inhabitants of the area harvested shellfish at increasingly high rates to provide the material basis for a series of ritual interventions that aimed to circumvent the effects of rapid social and ecological change.     

The expansion of Araucaria forest in the southern Brazilian highlands during the last 4000 years and its implications for the development of the Taquara/Itararé Tradition

Abstract

An examination of the late Holocene environmental and cultural sequences of the southern Brazilian highlands indicates that the colonisation of this region by the Taquara/Itararé people is associated with the expansion of Araucaria forest resulting from the onset of wetter climatic conditions in the region, which started between around 1410 and 900 cal. yr BP. The more intense and permanent human occupation of this region is associated with the advance of Araucaria forest, which provided Taquara/Itararé groups with a newly abundant and reliable resource: Araucaria seeds. In addition, we review the evidence for landscape transformation associated with the beginning of food-production in the region. Charcoal records show that local populations may have practiced slash-and-burn agriculture at lower elevations since the beginning of the late Holocene around 4320 cal. yr BP, and continued this practice during the second part of the late Holocene.