Matching Items (10)

156876-Thumbnail Image.png

Abiotic and Biotic Drivers of Turnover and Community Assembly in African Mammals

Description

Climate and environmental forcing are widely accepted to be important drivers of evolutionary and ecological change in mammal communities over geologic time scales. This paradigm has been particularly influential in

Climate and environmental forcing are widely accepted to be important drivers of evolutionary and ecological change in mammal communities over geologic time scales. This paradigm has been particularly influential in studies of the eastern African late Cenozoic fossil record, in which aridification, increasing seasonality, and C4 grassland expansion are seen as having shaped the major patterns of human and faunal evolution. Despite the ubiquity of studies linking climate and environmental forcing to evolutionary and ecological shifts in the mammalian fossil record, many central components of this paradigm remain untested or poorly developed. To fill this gap, this dissertation employs biogeographical and macroecological analyses of present-day African mammal communities as a lens for understanding how abiotic change may have shaped community turnover and structure in the eastern African Plio-Pleistocene. Three dissertation papers address: 1) the role of ecological niche breadth in shaping divergent patterns of macroevolutionary turnover across clades; 2) the effect of climatic and environmental gradients on community assembly; 3) the relative influence of paleo- versus present-day climates in structuring contemporary patterns of community diversity. Results of these papers call into question many tenets of current theory, particularly: 1) that niche breadth differences (and, by extension, their influence on allopatric speciation) are important drivers of macroevolution, 2) that climate is more important than biotic interactions in community assembly, and 3) that communities today are in equilibrium with present-day climates. These findings highlight the need to critically reevaluate the role and scale-dependence of climate in mammal evolution and community ecology and to carefully consider potential time lags and disequilibrium dynamics in the fossil record.

Contributors

Agent

Created

Date Created
  • 2018

151483-Thumbnail Image.png

Tracking climate-driven changes in Neandertal subsistence behaviors and prey mobility patterns

Description

The ability of Neandertals to cope with the oscillating climate of the late Pleistocene and the extent to which these climate changes affected local Neandertal habitats remain unanswered anthropological topics

The ability of Neandertals to cope with the oscillating climate of the late Pleistocene and the extent to which these climate changes affected local Neandertal habitats remain unanswered anthropological topics of considerable scientific interest. Understanding the impact of climatic instability on Neandertals is critical for reconstructing the behaviors of our closest fossil relatives and possibly identifying factors that contributed to their extinction. My work aimed to test the hypotheses that 1) cold climates stressed Neandertal populations, and 2) that global climate changes affected local Neandertal habitats. An analysis of Neandertal butchering on Cervus elaphus, Rangifer tarandus, and Capreolus capreolus skeletal material deposited during global warm and cold phases from two French sites - Pech de l'Azé IV and Roc de Marsal - was conducted to assess the impact of climate change on butchering strategies and resource extraction. Results from a statistical analysis of surface modification on all marrow yielding long bones, including the 1st phalanx, demonstrated that specimens excavated from the cold levels at each cave have more cut marks (Wald χ2= 51.33, p= <0.001) and percussion marks (Wald χ2= 4.92, p= 0.02) than specimens from the warm levels after controlling for fragment size. These results support the hypothesis that Neandertals were nutritionally stressed during glacial cycles. The hypothesis that global climates affected local habitats was tested through radiogenic strontium isotopic reconstruction of large herbivore mobility patterns (e.g., Bison, Equus, Cervus and Rangifer), because it is known that in the northern hemisphere, mammals migrate less in warm, well-vegetated environments, but more in cold, open environments. Identifying isotopic variation in mammalian fossils enables mobility patterns to be inferred, providing an indication of whether environments at Pech de l'Azé IV and Roc de Marsal tracked global climates. Results from this study indicate that Neandertal prey species within the Dordogne Valley of France did not undertake long distance round-trip migrations in glacial or interglacial cycles, maintaining the possibility that local habitats did not change in differing climatic cycles. However, because Neandertals were nutritionally stressed the most likely conclusion is that glacial cycles decreased herbivore populations, thus stressing Neandertals.

Contributors

Agent

Created

Date Created
  • 2012

154193-Thumbnail Image.png

Stable isotope analysis of archaeological and modern micromammals from the Greater Cape Floristic Region near Pinnacle Point, on the south coast of South Africa

Description

The Middle Stone Age archaeological record from the south coast of South Africa contains significant evidence for early modern human behavior. The south coast is within the modern Greater Cape

The Middle Stone Age archaeological record from the south coast of South Africa contains significant evidence for early modern human behavior. The south coast is within the modern Greater Cape Floristic Region (GCFR), which in the present-day encompasses the entirety of South Africa’s Winter Rainfall Zone (WRZ) and contains unique vegetation elements that have been hypothesized to be of high utility to hunter-gatherer populations. Extant paleoenvironmental proxy records for the Pleistocene in the region often indicate evidence for more open environments during the past than occur in the area in the present-day, while climate models suggest glacial presence of the WRZ that would support maintenance of C3-predominant GCFR vegetation.

These paleoenvironmental proxies sample past environments at geographic scales that are often regional. The GCFR flora is hyper-diverse, and glacial climate change-driven impacts on local vegetation could have been highly variable over relatively small geographic scales. Proxy records that are circumscribed in their geographic scale are thus key to our understanding of ancient environments at particular MSA archaeological localities.

Micromammal fossil teeth are now recognized as an abundant potential reservoir of paleoenvironmental proxy data at an extremely local scale. This study analyzed modern micromammal teeth obtained from raptor pellets at three locations on the south coast. Stable carbon isotope analysis indicates that the modern micromammals from the taxa sampled consume a wide range of δ13Cplant on the landscape when it is available, and thus stable carbon isotope analysis of micromammal teeth should act as a proxy for the range of available δ13Cdiet in a circumscribed area of vegetation.

Micromammal stable carbon isotope data obtained from specimens from one of the few well-dated MIS6-MIS5 sequences in the region (Pinnacle Point sites 13B, 30, and 9C). δ13Cenamel values for the taxa sampled indicate diets that are primarily C3, and there is almost no evidence for a dietary C4 grass component in any of the sampled specimens. This indicates that, at a minimum, pockets of C3 vegetation associated with the GCFR were likely available to hunter-gatherers at Pinnacle Point throughout the Middle and Late Pleistocene.

Contributors

Agent

Created

Date Created
  • 2015

A semiotic approach to the evolution of symboling capacities during the late Pleistocene with implications for claims of modernity in early human groups

Description

This research uses Peircean Semiotics to model the evolution of symbolic behavior in the human lineage and the potential material correlates of this evolutionary process in the archaeological record. The

This research uses Peircean Semiotics to model the evolution of symbolic behavior in the human lineage and the potential material correlates of this evolutionary process in the archaeological record. The semiotic model states the capacity for symbolic behavior developed in two distinct stages. Emergent capacities are characterized by the sporadic use of non-symbolic and symbolic material culture that affects information exchange between individuals. Symbolic exchange will be rare. Mobilized capacities are defined by the constant use of non-symbolic and symbolic objects that affect both interpersonal and group-level information exchange. Symbolic behavior will be obligatory and widespread. The model was tested against the published archaeological record dating from ~200,000 years ago to the Pleistocene/Holocene boundary in three sub-regions of Africa and Eurasia. A number of Exploratory and Confirmatory Data Analysis techniques were used to identify patterning in artifacts through time consistent with model predictions. The results indicate Emergent symboling capacities were expressed as early as ~100,000 years ago in Southern Africa and the Levant. However, capacities do not appear fully Mobilized in these regions until ~17,000 years ago. Emergent symboling is not evident in the European record until ~42,000 years ago, but develops rapidly. The results also indicate both Anatomically Modern Humans and Neanderthals had the capacity for symbolic behavior, but expressed those capacities differently. Moreover, interactions between the two populations did not select for symbolic expression, nor did periodic aggregation within groups. The analysis ultimately situates the capacity for symbolic behavior in increased engagement with materiality and the ability to recognize material objects can be made meaningful– an ability that must have been shared with Anatomically Modern Humans’ and Neanderthals’ most recent common ancestor. Consequently, the results have significant implications for notions of ‘modernity’ and human uniqueness that drive human origins research. This work pioneers deductive approaches to cognitive evolution, and both strengths and weaknesses are discussed. In offering notable results and best practices, it effectively operationalizes the semiotic model as a viable analytical method for human origins research.

Contributors

Agent

Created

Date Created
  • 2016

154204-Thumbnail Image.png

Late Pleistocene hunter-gatherer settlement and ecology of the Romanian Carpathians and adjacent areas

Description

Despite nearly five decades of archaeological research in the Romanian Carpathian basin and adjacent areas, how human foragers organized their stone artifact technologies under varying environmental conditions remains poorly understood.

Despite nearly five decades of archaeological research in the Romanian Carpathian basin and adjacent areas, how human foragers organized their stone artifact technologies under varying environmental conditions remains poorly understood.

Some broad generalizations have been made; most work in the region is concerned primarily with descriptive and definitional issues rather than efforts to explain past human behavior or human-environmental interactions. Modern research directed towards understanding human adaptation to different environments remains in its infancy. Grounded in the powerful conceptual framework of evolutionary ecology and utilizing recent methodological advances, this work has shown that shifts in land-use strategies changes the opportunities for social and biological interaction among Late Pleistocene hominins in western Eurasia, bringing with it a plethora of important consequences for cultural and biological evolution.

I employ, in my Dissertation, theoretical and methodological advances derived from human behavioral ecology (HBE) and lithic technology organization to show how variability in lithic technology can explain differences in technoeconomic choices and land-use strategies of Late Pleistocene foragers in Romanian Carpathians Basin and adjacent areas. Set against the backdrop of paleoenvironmental change, the principal questions I addressed are whether or not technological variation at the beginning of the Upper Paleolithic can account for fundamental changes at its end.

The analysis of the Middle and Upper Paleolithic strata, from six archaeological sites, shows that the lithic industries were different not because of biocultural differences in technological organization, landuse strategies, and organizational flexibility. Instead the evidence suggests that technoeconomic strategies, the intensity of artifact curation and how foragers used the land appear to have been more closely related to changing environmental conditions, task-specific activities, and duration of occupation. This agrees well with the results of studies conducted in other areas and with those predicted from theoretically-derived models based on evolutionary ecology. My results lead to the conclusion that human landuse effectively changes the environment of selection for hominins and their lithic technologies, an important component of the interface between humans and the natural world. Foragers move across the landscape in comparable ways in very different ecological settings, cross-cutting both biological morphotypes and prehistorian-defined analytical units.

Contributors

Agent

Created

Date Created
  • 2015

154295-Thumbnail Image.png

Landscape variability in tool-use and edge damage formation in South African Middle Stone Age lithic sssemblages

Description

This study explores how early modern humans used stone tool technology to adapt to changing climates and coastlines in the Middle Stone Age of South Africa. The MSA is associated

This study explores how early modern humans used stone tool technology to adapt to changing climates and coastlines in the Middle Stone Age of South Africa. The MSA is associated with the earliest fossil evidence for modern humans and complex cultural behaviors during a time period of dramatic climate change. Human culture allows for the creation, use, and transmission of technological knowledge that can evolve with changing environmental conditions. Understanding the interactions between technology and the environment is essential to illuminating the role of culture during the origin of our species. This study is focused on understanding ancient tool use from the study of lithic edge damage patterns at archaeological assemblages in southern Africa by using image-based quantitative methods for analyzing stone tools. An extensive experimental program using replicated stone tools provides the comparative linkages between the archaeological artifacts and the tasks for which they were used. MSA foragers structured their tool use and discard behaviors on the landscape in several ways – by using and discarding hunting tools more frequently in the field rather than in caves/rockshelters, but similarly in coastal and interior contexts. This study provides evidence that during a significant microlithic technological shift seen in southern Africa at ~75,000 years ago, new technologies were developed alongside rather than replacing existing technologies. These results are compared with aspects of the European archaeological record at this time to identify features of early human technological behavior that may be unique to the evolutionary history of our species.

Contributors

Agent

Created

Date Created
  • 2016

157490-Thumbnail Image.png

Probability Models of Bone Surface Modification and Application to Fossil Evidence from Ledi-Geraru (2.82 Ma) and Dikika (3.39 Ma), Afar Ethiopia

Description

Two of the defining behaviors associated with the hominin lineage are an increased reliance on tool use and the routine incorporation of animal tissue in the diet. These adaptations have

Two of the defining behaviors associated with the hominin lineage are an increased reliance on tool use and the routine incorporation of animal tissue in the diet. These adaptations have been linked to numerous downstream consequences including key physiological adaptations as well as social and cognitive effects associated with modern humans. Thus, a critical issue in human evolution is how to determine when hominins began incorporating significant amounts of meat into their diets. Bone surface modifications (BSM) have long been recognized as a powerful inferential tool in identifying the differential involvement of actors responsible for altering assemblages of bone recovered from both archaeological and paleontological contexts and remain a primary source of direct evidence for butchery activities. Thus, determining the spatiotemporal context of increased carnivory in the hominin lineage relies on the accurate identification of fossil BSM.

Multidecade-long debates over the agents responsible for individual BSM indicate systemic flaws in historical approaches to identification. These debates are in part due to the extreme morphological overlap between BSM produced by certain agents of modification. The primary goal of this dissertation project therefore, is to construct probability models of BSM capable of identifying individual marks with an associated probability of assignment. Using a multivariate Bayesian approach to analyze experimentally-generated BSM data, this dissertation uses two different models, one incorporating both two and three-dimensional (3D) metric and attribute data associated with individual BSM and a second model comparing 3D geometric morphometric (GM) shape data associated with BSM.

The 2D/3D attribute model of BSM is used evaluate an assemblage of fossil BSM recovered from the Ledi-Geraru research area, Ethiopia (2.82 Ma) in spatiotemporal association with early Homo. The results of the analysis reveal compelling evidence for early butchery activities, suggesting hominins may have been using both modified and unmodified stone implements to process carcasses.

The second model, based upon 3D GM data, was used to evaluate the earliest purported evidence for stone-mediated butchery at Dikika, Ethiopia (3.39 Ma). The Dikika marks have been argued to be the result of crocodile feeding, trampling, and butchery by three different research groups. The 3D GM model evaluates the likelihood of each of these actors in the production of the controversial Dikika marks.

Contributors

Agent

Created

Date Created
  • 2019

151087-Thumbnail Image.png

The role of ochre in the development of modern human behavior: a case study from South Africa

Description

In recent years, southern Africa has figured prominently in the modern human origins debate due to increasing evidence for precocious behaviors considered to be unique to our species. These significant

In recent years, southern Africa has figured prominently in the modern human origins debate due to increasing evidence for precocious behaviors considered to be unique to our species. These significant findings have included bone tools, shell beads, engraved ostrich eggshell, and heavily ground and engraved ochre fragments. The presence of ochre in Middle Stone Age (MSA, ~250-40kya) archaeological sites in southern Africa is often proposed as indirect evidence for the emergence of symbolic or artistic behavior, a uniquely modern human trait. However, there is no remaining artwork from this period and there is significant debate about what the ochre may have been used for. With a few exceptions, ochre has gone largely unstudied. This project tested competing models for ochre use within the Pinnacle Point (PP), South Africa research area. Combined results from characterization and sourcing analyses, color classification, heat treatment analysis, and hafting experiments suggest MSA ochre is tied to early symbolic or ritual behavior.

Contributors

Agent

Created

Date Created
  • 2012

156442-Thumbnail Image.png

Zooarchaeological and taphonomic analyses of Pleistocene vertebrate fauna from the Middle and Later Stone Age occupations at Contrebandiers Cave, Atlantic coast, Morocco

Description

This dissertation research describes the hunting behavior of early modern humans through the analysis of vertebrate faunal remains from Contrebandiers Cave, Morocco. Contrebandiers Cave is located in the town of

This dissertation research describes the hunting behavior of early modern humans through the analysis of vertebrate faunal remains from Contrebandiers Cave, Morocco. Contrebandiers Cave is located in the town of Témara and is roughly 250 meters from the current shoreline of the Atlantic Ocean. The cave was excavated in the 1950s and 1970s by l’Abbé Roche, and again starting in 2007 by Dibble and El Hajraoui with total station plotting of finds. Contrebandiers Cave contains Middle Stone Age (MSA) deposits dated to Marine Isotope Stages (MIS) 5e, 5d and 5c, ~120,000 to ~96,000 years ago. The Later Stone Age (LSA) deposits are dated to MIS 2, ~20,000 years ago. The entirety of the ~12,000 vertebrate faunal remains from Dibble and El Hajraoui’s excavation were analyzed for taxonomic and taphonomic identification.

A total of 67 vertebrate taxa were identified and include ungulates, carnivores, lagomorphs, birds, tortoises, snakes and fish. The faunal remains from Contrebandiers Cave preserve surface modification that indicates both humans and carnivores acted as agents of prey accumulation. Skeletal element representation and surface modification of ungulate remains suggest that humans had primary access to small, medium and large-bodied prey. In the MSA levels, carnivore skeletal remains preserve surface modification that is interpreted as being indicative of behavior associated with skinning for fur removal.

The vertebrate faunal remains from MIS 5e and 5d indicate that humans were hunting grazers and mixed feeders from open habitats and suids from mixed habitats. The faunal remains from MIS 5c indicate that humans focused less on suids and more on mixed feeders from open habitats. The vertebrate faunal remains from MIS 2 reveal humans hunting grazers from dry, open habitats. This research provides a description of human hunting behavior in North Africa, and contributes to our understanding of early modern human behavior prior to dispersal out of Africa.

Contributors

Agent

Created

Date Created
  • 2018

A formal modeling approach to understanding stone tool raw material selection in the African Middle Stone Age: a case study from Pinnacle Point, South Africa

Description

The South African Middle Stone Age (MSA), spanning the Middle to Late Pleistocene (Marine Isotope Stages (MIS) 8-3) witnessed major climatic and environmental change and dramatic change in forager technological

The South African Middle Stone Age (MSA), spanning the Middle to Late Pleistocene (Marine Isotope Stages (MIS) 8-3) witnessed major climatic and environmental change and dramatic change in forager technological organization including lithic raw material selection. Homo sapiens emerged during the MSA and had to make decisions about how to organize technology to cope with environmental stressors, including lithic raw material selection, which can effect tool production and application, and mobility.

This project studied the role and importance of lithic raw materials in the technological organization of foragers by focusing on why lithic raw material selection sometimes changed when the behavioral and environmental context changed. The study used the Pinnacle Point (PP) MSA record (MIS6-3) in the Mossel Bay region, South Africa as the test case. In this region, quartzite and silcrete with dramatically different properties were the two most frequently exploited raw materials, and their relative abundances change significantly through time. Several explanations intertwined with major research questions over the origins of modern humans have been proposed for this change.

Two alternative lithic raw material procurement models were considered. The first, a computational model termed the Opportunistic Acquisition Model, posits that archaeological lithic raw material frequencies are due to opportunistic encounters during random walk. The second, an analytical model termed the Active-Choice Model drawn from the principles of Optimal Foraging Theory, posits that given a choice, individuals will choose the most cost effective means of producing durable cutting tools in their environment and will strategically select those raw materials.

An evaluation of the competing models found that lithic raw material selection was a strategic behavior in the PP record. In MIS6 and MIS5, the selection of quartzite was driven by travel and search cost, while during the MIS4, the joint selection of quartzite and silcrete was facilitated by a mobility strategy that focused on longer or more frequent stays at PP coupled with place provisioning. Further, the result suggests that specific raw materials and technology were relied on to obtain food resources and perform processing tasks suggesting knowledge about raw material properties and suitability for tasks.

Contributors

Agent

Created

Date Created
  • 2017