Climate change and agropastoralist settlement in the Shashe-Limpopo River Basin, southern Africa: AD 880 to 1700

The expansion and decline of complex socio-political farming systems in the Shashe-Limpopo River Basin, southern Africa, has been linked to large-scale climate shifts in which increased rainfall favoured intensified agropastoral production and expanded settlement, while the onset of arid conditions led to collapse and abandonment of the area. This study uses stable nitrogen isotope ratios (C5Nf4N) from modern and archaeological fauna to construct a proxy-rainfall sequence for the region from AD 880 onwards. The resulting sequence provides a revised climatic context for agropastoral settlement of the river basin and evidence of greater climatic variation than previously documented. Stable nitrogen isotope data from the bone collagen of archaeological fauna show that settlement by Zhizo agropastoralists between AD 880 and 1010 took place under semi-arid conditions, with average annual rainfall of <500 mm. Results for sites dating between AD 1010 to 1290 are consistent with previous interpretations that the Leopard's Kopje A and B cultural period 'capitals' of K2 and Mapungubwe, respectively, rose to prominence under a trend towards increased average annual rainfall that was 2500 mm. The data indicate also that the phase of increased moisture extended beyond the abandonment of Mapungubwe at AD 1290 and continued to be evident in fauna dating to the Moloko/Icon cultural period between AD 1310 and 1415. Data from the Moloko/Khami cultural period sites suggest that markedly drier conditions were not evident in the area until after AD 1450. Based on the isotope data, increased rainfall appears to have coincided with the expansion and intensification of settlement in the Shashe-Limpopo River Basin. Reconsideration, however, needs to be given to the correlation between the abandonment of Mapungubwe with the onset of arid conditions unfavourable for agropastoralism; other explanations, encompassing socio-economic and political choices, also must be sought

Protocol for sectioning human dentine: expanded from Methods 1 and 2

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Using carbon isotope data of fossil bovid communities for palaeoenvironmental reconstruction

Reconstructing palaeoenvironments is a major focus of palaeoanthropological research. While many techniques are now available for exploring past environments, fossil bovids remain amongst the most widely utilized sources of environmental information. Most studies of fossil bovids, however, assume implicitly that bovid ecology is the same now as it was in the distant past. Because such uniformitarianist assumptions are not always valid, we have developed a method to provide palaeoenvironmental information from fossil bovids that requires no ecological assumptions. Here, we show that the percentages of C3 and C4 vegetation-consuming bovids in modern environments generally vary according to the amount of woody vegetation present. Application of this C3 / C4 index to the fossil bovid assemblage at Makapansgat shows that, based on carbon isotope data, the percentage of C3-consuming bovids is high, suggesting a great deal of woody vegetation in this vicinity about 3 million years ago

Utilization of savanna-based resources by Plio-Pleistocene baboons

We have determined the tooth enamel carbonate 13C values of five cercopithecoid taxa from the Plio-Pleistocene deposits of Swartkrans Members 1 and 2 and Sterkfontein Member 4. These data were used to determine the relative proportions of C3 and C4 biomass consumed by extinct baboons and contemporary non-human primates. We compared these results with data on modern Papio hamadryas ursinus from different savanna areas in South Africa, as well as with published isotopic data and dietary interpretations based on molar morphology of these taxa. The data reveal little evidence for use of grasses or grass-based foods by modern South African baboons. The fossil papionins Papio hamadryas robinsoni, Papio (Dinopithecus) ingens, and Parapapio spp., however, utilized more savanna-based C4 resources than previously predicted (particularly in the case of P. (D.) ingens). Theropithecus oswaldi had 13C values depicting, as expected, a largely grass-based diet, and we confirm earlier conclusions that this species incorporated a wider range of food items into its diet than do modern T. gelada, as reported in the literature. The colobine monkey, Cercopithecoides williamsi, made extensive use of savanna-.based C4 foods, confirming some degree of terrestrial foraging by the species

Micromilling vs hand drilling in stable isotope analyses of incremental carbonates: The potential for δ ¹³ C contamination by embedding resin

RationaleEmbedding resins are commonly used to facilitate high-resolution sampling for stable isotope analysis but anomalous δ13C values have been observed in some cases. Here we compare the results of microsampling strategies for hand-drilled versus resin-embedded micromilled samples from the same marine shells to assess whether resin contamination is implicated in δ13C spikes. The comparison allows assessment of the relative benefits for spatial resolution, seasonal range for both δ18O and δ13C, and sample failure rates.MethodsHand-drilled samples were obtained from two bivalve shells (Spisula sachalinensis), corresponding to micromilled samples on the same shells where high δ13C spikes were observed. All carbonate powders were analysed using a dual-inlet Isoprime mass spectrometer and Multiprep device. Results from both sample sets were compared statistically.ResultsNo anomalous high δ13C values and no failures due to insufficient gas were observed in the hand-drilled samples in contrast to the embedded micromilled sequences. Spatial resolution was reduced (~2.5×) in the former compared with the latter, resulting in a small reduction in the total range observed in the micromilled δ13C and δ18O values. Reduced sampling resolution between the two datasets was only significant for δ18O.ConclusionsFor S. sachalinensis (as with other similar bivalves), rapid growth mitigates the reduced sampling resolution of hand drilling and does not significantly impact observed isotopic range and seasonal patterning. Occurrence of anomalous δ13C values were eliminated and failure rates due to insufficient sample size greatly reduced in the hand-drilled dataset. We can find no other explanation for the occurrence of δ13C spikes than contamination by the embedding agent. We conclude that the logistical and interpretational benefits of careful hand drilling may be preferable to resin embedding for micromilling in marine shells, corals or speleothems where growth rate is rapid and the highest resolution is not required

Stable carbon isotope reconstruction of ungulate diet changes through the seasonal cycle

We analysed stable carbon isotope ratios (ð13C) in faeces of 11 African ungulate species from three South African savanna environments to determine whether this approach is sufficiently sensitive to record short-term seasonal diet changes in browsers (BR), mixed-feeders (IM), and grazers (GR). At monthly intervals, faecal ð13C revealed variations in proportions of C3 (browse) to C4 (grass) biomass consumed that were not detected by broader dry versus wet season comparisons, including subtle diet shifts amongst BR and GR. However, trends in faeces were influenced by changes in C3 and C4 plant isotope composition of up to 3‰. Nonetheless, faeces and plants showed strongly similar patterns of variation through the seasonal cycle, so that small diet shifts can be reliably inferred, provided that the variations in plants are controlled for. Faecal ð13C of BR may be further influenced by consumption of isotopically different plant parts such as foliage versus fruit and flowers, and GR faeces may reflect differential utilization of grass following different photosynthetic sub-pathways. Future studies will need to incorporate data that capture isotopic variations in herbivore food sources, and if this is achieved, the approach may well become adopted as a routine addition to traditional methods for assessing diet, habitat use, and habitat condition

Mapping the Elephants of the 19th Century East African Ivory Trade with a Multi-Isotope Approach.

East African elephants have been hunted for their ivory for millennia but the nineteenth century witnessed strongly escalating demand from Europe and North America. It has been suggested that one consequence was that by the 1880s elephant herds along the coast had become scarce, and to meet demand, trade caravans trekked farther into interior regions of East Africa, extending the extraction frontier. The steady decimation of elephant populations coupled with the extension of trade networks have also been claimed to have triggered significant ecological and socio-economic changes that left lasting legacies across the region. To explore the feasibility of using an isotopic approach to uncover a 'moving frontier' of elephant extraction, we constructed a baseline isotope data set (δ13C, δ15N, δ18O and 87Sr/86Sr) for historic East African elephants known to have come from three distinct regions (coastal, Rift Valley, and inland Lakes). Using the isotope results with other climate data and geographical mapping tools, it was possible to characterise elephants from different habitats across the region. This baseline data set was then used to provenance elephant ivory of unknown geographical provenance that was exported from East Africa during the late nineteenth and early twentieth centuries to determine its likely origin. This produced a better understanding of historic elephant geography in the region, and the data have the potential to be used to provenance older archaeological ivories, and to inform contemporary elephant conservation strategies.Funding: This research was funded by a European Union Marie Curie Excellence grant (MEXT-CT-2006-042704) awarded to PJL for the Historical Ecologies of East African Landscapes (HEEAL) project (http://cordis.europa.eu/project/rcn/83961_en.html). Additional funding came from the Worldwide Universities Network Research Mobility programme and the Smithsonian Institution Fellowship programme awarded to ANC. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Note: This funding was not held by UCAM

Historical Tropical Forest Reliance amongst the Wanniyalaeto (Vedda) of Sri Lanka: an Isotopic Perspective.

Headland and Bailey (1991) argued in Human Ecology that tropical forests could not support long-term human foraging in the absence of agriculture. Part of their thesis was based on the fact that supposedly isolated 'forest' foragers, such as the Wanniyalaeto (or Vedda) peoples of Sri Lanka, could be demonstrated to be enmeshed within historical trade networks and rely on crops as part of their overall subsistence. Yet, in the same volume and in the years that followed scholars have presented ethnographic and archaeological evidence, including from Sri Lanka, that counter this proposition, demonstrating the occupation and exploitation of tropical rainforest environments back to 38,000 years ago (ka) in this part of the world. However, archaeological and ethnohistorical research has yet to quantify the overall reliance of human foragers on tropical forest resources through time. Here, we report stable carbon and oxygen isotope data from historical Wanniyalaeto individuals from Sri Lanka, in full collaboration with the present-day members of this group, that suggest that while a number of individuals made use of agricultural resources in the recent past, others subsisted primarily on tropical forest resources as late as the 1800s.Max Planck Society Natural Environmental Research Council Boise Fund, University of Oxford European Research Counci

Dating human occupation and adaptation in the southern European last glacial refuge : The chronostratigraphy of Grotta del Romito (Italy)

Grotta del Romito has been the subject of numerous archaeological, chronological and palaeoenvironmental investigations for more than a decade. During the Upper Palaeolithic period the site contains evidence of human occupation through the Gravettian and Epigravettian periods, multiple human burials, changes in the pattern of human occupation, and faunal, isotopic and sedimentological evidence for local environmental change. In spite of this rich record, the chronological control is insufficient to resolve shifts in subsistence and mobility patterns at sufficiently high resolution to match the abrupt climate fluctuations at this time. To resolve this we present new radiocarbon and tephrostratigraphic dates in combination with existing radiocarbon dates, and develop a Bayesian age model framework for the site. This improved chronology reveals that local environmental conditions reflect abrupt and long-term changes in climate, and that these also directly influence changing patterns of human occupation of the site. In particular, we show that the environmental record for the site, based on small mammal habitat preferences, is chronologically in phase with the main changes in climate and environment seen in key regional archives from Italy and Greenland. We also calculate the timing of the transitions between different cultural phases and their spans. We also show that the intensification in occupation of the site is chronologically coincident with a rapid rise in Mesic Woody taxa seen in key regional pollen records and is associated with the Late Epigravettian occupation of the site. This change in the record of Grotta del Romito is also closely associated stratigraphically with a new tephra (the ROM-D30 tephra), which may act as a critical marker in environmental records of the region