Microhabitat variability in Human Evolution

Climate variability and hominin evolution are inextricably linked. Yet, hypotheses examining the impact of large-scale climate shifts on hominin landscape ecology are often constrained by proxy data coming from off-site lake and ocean cores and temporal offsets between paleoenvironmental and archaeological records. Additionally, landscape response data (most commonly, records of vegetation change), are often used as a climate proxy. This is problematic as it assumes that vegetation change signifies global or regional climate shifts without accounting for the known non-linear behavior of ecological systems and the often-significant spatial heterogeneity in habitat structure and response. The exploitation of diverse, rapidly changing habitats by Homo by at least two million years ago highlights that the ability to adapt to landscapes in flux had emerged by the time of our genus’ African origin. To understand ecosystem response to climate variability, and hominin adaptations to environmental complexity and ecological diversity, we need cross-disciplinary datasets in direct association with stratified archaeological and fossil assemblages at a variety of temporal and spatial scales. In this article, we propose a microhabitat variability framework for understanding Homo’s adaptability to fluctuating climates, environments, and resource bases. We argue that the exploitation of microhabitats, or unique ecologically and geographically defined areas within larger habitats and ecoregions, was a key skill that allowed Homo to adapt to multiple climates zones and ecoregions within and beyond Africa throughout the Pleistocene.Introduction Microhabitat variability - Identifying Microhabitat Variability Environmental and climate variability and human evolution Ecosystem resilience in face of climate change Microhabit at variability and human evolution - Microhabitat Variability at Oldupai Gorge: A Case Study Expanding the microhabitat variability framework Conclusio

Oldowan Technology Amid Shifting Environments ∼2.03–1.83 Million Years Ago

The Oldowan represents the earliest recurrent evidence of human material culture and one of the longest-lasting forms of technology. Its appearance across the African continent amid the Plio-Pleistocene profound ecological transformations, and posterior dispersal throughout the Old World is at the foundation of hominin technological dependence. However, uncertainties exist concerning the degree to which the Oldowan constitutes an environment-driven behavioral adaptation. Moreover, it is necessary to understand how Oldowan technology varied through time in response to hominin ecological demands. In this study, we present the stone tool assemblage from Ewass Oldupa, a recently discovered archeological site that signals the earliest hominin occupation of Oldupai Gorge (formerly Olduvai) ∼2.03 Ma. At Ewass Oldupa, hominins underwent marked environmental shifts over the course of a ∼200 kyr period. In this article, we deployed an analysis that combines technological and typological descriptions with an innovative quantitative approach, the Volumetric Reconstruction Method. Our results indicate that hominins overcame major ecological challenges while relying on technological strategies that remained essentially unchanged. This highlights the Oldowan efficiency, as its basic set of technological traits was able to sustain hominins throughout multiple environments.Introduction Ewass Oldupa Materials and methods - Stone Tool Techno-Typological Analysis - The Volumetric Reconstruction Method Results - Assemblage Overview - Techno-Typological Variation Over Time and Across Environments - The Volumetric Reconstruction Method Discussio

Microbotanical residues for the study of early hominin tools

More than 2 million years ago in East Africa, the earliest hominin stone tools evolved amidst changes in resource base, with pounding technology playing a key role in this adaptive process. Olduvai Gorge (now Oldupai) is a famed locality that remains paramount for the study of human evolution, also yielding some of the oldest battering tools in the world. However, direct evidence of the resources processed with these technologies is lacking entirely. One way to obtain this evidence is through the analysis of surviving residues. Yet, linking residues with past processing activities is not simple. In the case of plant exploitation, this link can only be established by assessing site-based reference collections inclusive of both anthropogenic and natural residues as a necessary first step and comparative starting point. In this paper, we assess microbotanical remains from rock clasts sourced at the same quarry utilized by Oldowan hominins at Oldupai Gorge. We mapped this signal and analysed it quantitatively to classify its spatial distribution objectively, extracting proxies for taxonomic identification and further comparison with freestanding soils. In addition, we used blanks to manufacture pounding tools for blind, controlled replication of plant processing. We discovered that stone blanks are in fact environmental reservoirs in which plant remains are trapped by lithobionts, preserved as hardened accretions. Tool use, on the other hand, creates residue clusters; however, their spatial distribution can be discriminated from purely natural assemblages by the georeferencing of residues and statistical analysis of resulting patterns. To conclude, we provide a protocol for best practice and a workflow that has the advantage of overcoming environmental noise, reducing the risk of false positive, delivering a firm understanding of residues as polygenic mixtures, a reliable use of controls, and most importantly, a stronger link between microbotanical remains and stone tool use. © 2022. The Author(s).Materials and methods Results - Blanks as environmental reservoirs - Utilization creates residue clusters - Anthropogenic residue distribution - Of lichen habitability, proxy palimpsests, and hardened accretions - A protocol to study plant residue from Oldowan pounding tool

Earliest Olduvai hominins exploited unstable environments ~ 2 million years ago

Rapid environmental change is a catalyst for human evolution, driving dietary innovations, habitat diversification, and dispersal. However, there is a dearth of information to assess hominin adaptions to changing physiography during key evolutionary stages such as the early Pleistocene. Here we report a multiproxy dataset from Ewass Oldupa, in the Western Plio-Pleistocene rift basin of Olduvai Gorge (now Oldupai), Tanzania, to address this lacuna and offer an ecological perspective on human adaptability two million years ago. Oldupai’s earliest hominins sequentially inhabited the floodplains of sinuous channels, then river-influenced contexts, which now comprises the oldest palaeolake setting documented regionally. Early Oldowan tools reveal a homogenous technology to utilise diverse, rapidly changing environments that ranged from fern meadows to woodland mosaics, naturally burned landscapes, to lakeside woodland/palm groves as well as hyper-xeric steppes. Hominins periodically used emerging landscapes and disturbance biomes multiple times over 235,000 years, thus predating by more than 180,000 years the earliest known hominins and Oldowan industries from the Eastern side of the basin.Introduction Results - Stratigraphy and archaeology - Early Oldowan ecology at ~ 2 Ma Discussion Methods - Biomarkers - Energy dispersive X-ray fluorescence - Excavation - Fauna - Mineral geochemistry - Phytolith analysis - Pollen and microcharcoal - Stable carbon and oxygen isotope analysis of faunal dental enamel - Stone tool

Initial assessment of bioavailable strontium at Oldupai Gorge, Tanzania: potential for early mobility studies

Strontium isotope analysis is a useful tool for tracing mobility and migration in past populations. For it to be employed, the 87Sr/86Sr values of the landscape must be well-understood. Bioavailable strontium is a combination of geological and atmospheric strontium available for use by plants and animals. In this study we begin mapping bioavailable strontium values around the Oldupai Gorge region so that this method may be utilized on archaeological hominins and animals in the future. We analyzed three plants from 33 localities across volcanic and metamorphic bedrock, including the regional drainage sump, Olbalbal. We found that bioavailable strontium in the region is homogeneous overall, with trends towards increasing values to the north and northeast and in Olbalbal. There was no difference between 87Sr/86Sr values of metamorphic and volcanic areas. Migrants from outside the study area with different isotopic values will be easily identifiable from the local residents. As a proof of concept, we analyzed 7 animal teeth (hippopotamus, crocodile, and equid) from Engaji Nanyori, a Bed III and IV site at Oldupai Gorge. We found that enamel and dentine which had been acetic acid treated to remove diagenetic strontium were significantly different from one another. All animals had higher 87Sr/86Sr values than the plant values, suggesting that modern and ancient bioavailable strontium values may have been different, likely due to environmental differences.1. Introduction 2. Background 2.1. Using strontium values at the landscape level 2.2. Study area 2.3. Geology and palaeoanthropology 2.4. Palaeoenvironment and palaeoclimate 2.5. Engaji Nanyori 2.6. Plant and animal ecology 3. Materials and methods 3.1. Plant sampling 3.2. Excavation 3.3. Plant laboratory methods 3.4. Tooth preparation 3.5. Isotope analyses 3.6. Data analyses 4. Results 4.1. Bioavailable strontium 4.1.1. Geological variation 4.1.2. Geographical variation 4.1.3. Variation between plant types 4.2. Dental results 5. Discussion 5.1. Sources of variation 5.1.1. Bedrock 5.1.2. Atmospheric strontium 5.1.3. Hydrological strontium 5.1.4. Geographical factors 5.1.5. Plant and soil types 5.2. Dental tissues 5.2.1. Diagenesis 5.2.2. Taxonomy and migration 5.3. Modern vs. ancient bioavailable strontium 6. Conclusio

Structural characterization and decontamination of dental calculus for ancient starch research

Ancient dental calculus research currently relies on destructive techniques whereby archeological specimens are broken down to determine their contents. Two strategies that could partly remediate a permanent loss of the original sample and enhance future analysis and reproducibility include (1) structural surface characterization through spectroscopy along with crystallographic and spectroscopic analysis of its molecular structure, and (2) surface decontamination protocols in which the efficacy of cleaning dental calculus prior to extraction is demonstrated. Dental calculus provides ancient starch research a niche where granules may be adsorbed to minerals, coated, overgrown, entrapped, and/or protected from chemical degradation. While encapsulation offers protection from degradation, it does not shield the sample’s surface from contamination. The most common approach to retrieving microbotanical particles from archeological calculus has been the direct decalcification of the sample, after a cleaning stage variously consisting of immersion in water, acids, and mechanical dislodgment via gas, sonication, and/or toothbrushes. Little is known about the efficiency of these methods for a complete removal of sediment/soil and unrelated microbotanical matter. In this paper, controlled laboratory experimentation leads to chemical structural characterization and a decontamination protocol to eradicate starch granules. Several concentrations of acids, bases, and enzymes were tested at intervals to understand their potential to gelatinize and fully destroy starch granules; arriving at a procedure that effectively eradicates modern starch prior to dissolution without damaging the matrix or entrapped starch microremains. This is the first attempt at creating synthetic calculus to understand and systematically test effective decontamination protocols for ancient starch research

Petrographic Characterization of Raw Material Sources at Oldupai Gorge, Tanzania

Oldupai Gorge is located within the Ngorongoro Conservation Area, a UNESCO World Heritage Site in northern Tanzania along the western margin of the East African Rift System. Oldupai’s sedimentary record exhibits a complex sequence of inter-stratified lithic assemblages associated with the Early, Middle, and Later Stone Age. While diachronic technological change is perceptible, the totality of locally available rocks remained largely unchanged through time. Here, thin section petrography, Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy, and Electron Probe Micro Analysis were employed to characterize source lithologies in the Oldupai region. One of our goals was to determine if outcrops have rock types with unique mineral compositions amenable for sourcing lithic artifacts. Geological samples were collected in primary and secondary positions, from which sixty-two samples were selected for analysis. Comparative analyses show that five outcrops have quartzites with unique mineral compositions, seven meta-granite varieties are unique to five individual outcrops, Engelosin phonolite samples are texturally and mineralogically unique, and magmatic samples recovered in secondary position may be sourced to their volcanic center. Our results demonstrate it is feasible to differentiate between source materials using optical mineralogy which implies that sourcing lithic artifacts based on mineral compositions is possible. This is further substantiated by assigning the source/s for previously described fuchsitic quartzite artifacts from three archaeological sites at Oldupai as this raw material type uniquely occurs at two nearby outcrops. Systematic archaeological testing will allow future researchers to glean new understandings of hominin behavior and resource procurement within the Oldupai paleobasin