Micromilling vs hand drilling in stable isotope analyses of incremental carbonates: The potential for δ13 C contamination by embedding resin.

RATIONALE: Embedding resins are commonly used to facilitate high-resolution sampling for stable isotope analysis but anomalous δ13 C 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 δ13 C spikes. The comparison allows assessment of the relative benefits for spatial resolution, seasonal range for both δ18 O and δ13 C, and sample failure rates. METHODS: Hand-drilled samples were obtained from two bivalve shells (Spisula sachalinensis), corresponding to micromilled samples on the same shells where high δ13 C 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. RESULTS: No anomalous high δ13 C 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 δ13 C and δ18 O values. Reduced sampling resolution between the two datasets was only significant for δ18 O. CONCLUSIONS: For 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 δ13 C 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 δ13 C 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 isotopes reveal intensive pig husbandry practices in the middle Yellow River region by the Yangshao period (7000-5000 BP).

It is well-known that pigs (Sus scrofa) were domesticated very early in Neolithic China, but far less is known about the processes by which pig husbandry intensified so that pork became the most important animal protein for humans are less clear. Here, we explore pig feeding practices using the carbon and nitrogen isotope composition of bone collagen, focusing on developments in pig husbandry during the Yangshao period (7000-5000 BP) in the middle Yellow River region of China, and at the site of Xipo (5800-5000 BP) in particular. The results show that the diets of domestic pigs at Xipo were dominated by millet foods. Comparisons with other Yangshao sites in the region show a trend of increasing millet foddering for pigs throughout the Yangshao period. These results, and comparisons of the isotopic data for pigs against those for humans from the Xipo cemetery (5300-5000 BP), suggest that pigs were closely managed by humans. The evidence points to an intensification of Neolithic pig husbandry in the middle Yellow River region from this period.

'White gold' guano fertilizer drove agricultural intensification in the Atacama Desert from AD 1000.

The archaeological record shows that large pre-Inca agricultural systems supported settlements for centuries around the ravines and oases of northern Chile's hyperarid Atacama Desert. This raises questions about how such productivity was achieved and sustained, and its social implications. Using isotopic data of well-preserved ancient plant remains from Atacama sites, we show a dramatic increase in crop nitrogen isotope values (δ15N) from around AD 1000. Maize was most affected, with δ15N values as high as +30‰, and human bone collagen following a similar trend; moreover, their carbon isotope values (δ13C) indicate a considerable increase in the consumption of maize at the same time. We attribute the shift to extremely high δ15N values-the highest in the world for archaeological plants-to the use of seabird guano to fertilize crops. Guano-'white gold' as it came to be called-thus sustained agricultural intensification, supporting a substantial population in an otherwise extreme environment.

A guide for an anatomically sensitive dentine microsampling and age-alignment approach for human teeth isotopic sequences.

OBJECTIVES: Stable isotope analysis of sequential dentine samples is a potentially powerful method to reveal insights into early life-histories of individuals in the past. Dentine incremental growth structures are complex, however, and current approaches that apply horizontal sectioning of demineralized tooth halves or quarters risk combining multiple growth layers and may include unwanted cementum or secondary dentine. They also require destruction of large parts of a tooth. Here, we present a less destructive and relatively straightforward protocol that reduces damage, increases temporal resolution, and improves the accuracy of age-alignment between individuals. MATERIAL AND METHODS: We outline a protocol that includes the sampling of small (1 mm diameter) cylindrical plug transects from a thin section, along with an age-alignment scheme predicated on average growth rates for dentine areas. RESULTS AND DISCUSSION: The proposed protocol is readily applicable and more anatomically sensitive than horizontal slicing. Micro-samples are smaller (in both length and depth), hence minimizing temporal overlap and avoid directions that may contravene growth pattern. They completely avoid areas where secondary and tertiary dentine or cementum can be deposited. Age-alignment is improved by using growth ratios of anatomical tooth zones. CONCLUSION: This method minimizes destruction, enables finer temporal resolution and facilitates data comparison. It can be readily combined with fluorescence imaging-based or other pre-screening methods of dentine collagen preservation.

Towards a biologically available strontium isotope baseline for Ireland.

Strontium isotopes are used in archaeology, ecology, forensics, and other disciplines to study the origin of artefacts, humans, animals and food items. Strontium in animal and human tissues such as bone and teeth originates from food and drink consumed during life, leaving an isotopic signal corresponding to their geographical origin (i.e. where the plants grew, the animals grazed and the drinking water passed through). To contextualise the measurements obtained directly on animal and human remains, it is necessary to have a sound baseline of the isotopic variation of biologically available strontium in the landscape. In general, plants represent the main source of strontium for humans and animals as they usually contain much higher strontium concentrations than animal products (meat and milk) or drinking water. The observed difference between the strontium isotope composition of geological bedrock, soils and plants from the same locality warrants direct measurement of plants to create a reliable baseline. Here we present the first baseline of the biologically available strontium isotope composition for the island of Ireland based on 228 measurements on plants from 140 distinct locations. The isoscape shows significant variation in strontium isotope composition between different areas of Ireland with values as low as 0.7067 for the basalt outcrops in County Antrim and values of up to 0.7164 in the Mourne Mountains. This variability confirms the potential for studying mobility and landscape use of past human and animal populations in Ireland. Furthermore, in some cases, large differences were observed between different types of plants from the same location, highlighting the need to measure more than one plant sample per location for the creation of BASr baselines.

Seasonal scheduling of shellfish collection in the Middle and Later Stone Ages of southern Africa.

This study assesses the seasonal scheduling of shellfish harvesting among hunter-gatherer populations along the southernmost coast of South Africa, based on a large number of serial oxygen isotope analyses of marine mollusk shells from four archaeological sites. The south coast of South Africa boasts an exceptional record of coastal hunter-gatherer occupation spanning the Holocene, the last glacial cycle and beyond. The significance of coastal adaptations, in this region in particular, for later modern human evolution has been prominently debated. Shellfishing behaviors are an important focus for investigation given the dietary and scheduling implications and the abundant archaeological shell remains in numerous sites. Key to better understanding coastal foraging is whether it was limited to one particular season, or year-round. Yet, this has proven very difficult to establish by conventional archaeological methods. This study reconstructs seasonal harvesting patterns by calculating water temperatures from the final growth increment of shells. Results from two Later Stone Age sites, Nelson Bay Cave (together with the nearby Hoffman's Robberg Cave) and Byneskranskop 1, show a pronounced cool season signal, which is unexpected given previous ethnographic documentation of summer as the optimal season for shellfishing activities and inferences about hunter-gatherer scheduling and mobility in the late Holocene. Results from two Middle Stone Age sites, Klasies River and Pinnacle Point 5-6, show distinct seasonal patterns that likely reflect the seasonal availability of resources in the two locations. The Pinnacle Point 5-6 assemblage, which spans the MIS5-4 transition, records a marked shift in shellfishing seasonality at c. 71 ka that aligns with other indications of archaeological and environmental change at this time. We conclude that the scheduling and intensity of shellfishing in this region is affected by a suite of factors, including environmental and cultural drivers, rather than a single variable, such as population growth.

Fossil herbivore stable isotopes reveal middle Pleistocene hominin palaeoenvironment in 'Green Arabia'.

Despite its largely hyper-arid and inhospitable climate today, the Arabian Peninsula is emerging as an important area for investigating Pleistocene hominin dispersals. Recently, a member of our own species was found in northern Arabia dating to ca. 90 ka, while stone tools and fossil finds have hinted at an earlier, middle Pleistocene, hominin presence. However, there remain few direct insights into Pleistocene environments, and associated hominin adaptations, that accompanied the movement of populations into this region. Here, we apply stable carbon and oxygen isotope analysis to fossil mammal tooth enamel (n = 21) from the middle Pleistocene locality of Ti's al Ghadah in Saudi Arabia associated with newly discovered stone tools and probable cutmarks. The results demonstrate productive grasslands in the interior of the Arabian Peninsula ca. 300-500 ka, as well as aridity levels similar to those found in open savannah settings in eastern Africa today. The association between this palaeoenvironmental information and the earliest traces for hominin activity in this part of the world lead us to argue that middle Pleistocene hominin dispersals into the interior of the Arabian Peninsula required no major novel adaptation.

Strontium isotope analysis on cremated human remains from Stonehenge support links with west Wales.

Cremated human remains from Stonehenge provide direct evidence on the life of those few select individuals buried at this iconic Neolithic monument. The practice of cremation has, however, precluded the application of strontium isotope analysis of tooth enamel as the standard chemical approach to study their origin. New developments in strontium isotopic analysis of cremated bone reveal that at least 10 of the 25 cremated individuals analysed did not spend their lives on the Wessex chalk on which the monument is found. Combined with the archaeological evidence, we suggest that their most plausible origin lies in west Wales, the source of the bluestones erected in the early stage of the monument's construction. These results emphasise the importance of inter-regional connections involving the movement of both materials and people in the construction and use of Stonehenge.

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.

Did Our Species Evolve in Subdivided Populations across Africa, and Why Does It Matter?

We challenge the view that our species, Homo sapiens, evolved within a single population and/or region of Africa. The chronology and physical diversity of Pleistocene human fossils suggest that morphologically varied populations pertaining to the H. sapiens clade lived throughout Africa. Similarly, the African archaeological record demonstrates the polycentric origin and persistence of regionally distinct Pleistocene material culture in a variety of paleoecological settings. Genetic studies also indicate that present-day population structure within Africa extends to deep times, paralleling a paleoenvironmental record of shifting and fractured habitable zones. We argue that these fields support an emerging view of a highly structured African prehistory that should be considered in human evolutionary inferences, prompting new interpretations, questions, and interdisciplinary research directions.

Of cattle and feasts: Multi-isotope investigation of animal husbandry and communal feasting at Neolithic Makriyalos, northern Greece.

The aim of this study is to investigate livestock husbandry and its relationship to the mobilization of domestic animals for slaughter at large communal feasting events, in Late Neolithic Makriyalos, northern Greece. A multi-isotope approach is built that integrates analysis of: δ13C and δ15N values of human and animal bone collagen for understanding long-term dietary behavior,Incremental δ13C and δ18O values of domestic animal tooth enamel carbonate for assessing seasonal patterns in grazing habits and mobility, and87Sr/86Sr ratios of cattle tooth enamel for examining the possibility that some of the animals consumed at the site were born outside the local environment. The findings indicate that cattle had isotopically more variable diets than sheep, which may reflect grazing over a wider catchment area in the local landscape. Cattle products did not make a significant contribution to the long-term dietary protein intake of the humans, which may indicate that they were primarily consumed during episodic feasting events. There is no indication that pasturing of livestock was pre-determined by their eventual context of slaughter (i.e. large-scale feasting vs. more routine consumption events). Two non-local cattle identified among those deposited in a feasting context may have been brought to the site as contributions to these feasts. The evidence presented provides a more detailed insight into local land use and into the role of livestock and feasting in forging social relationships within the regional human population.

Publisher Correction: 78,000-year-old record of Middle and Later Stone Age innovation in an East African tropical forest.

The originally published version of this Article contained an error in Fig. 3, whereby an additional unrelated graph was overlaid on top of the magnetic susceptibility plot. Furthermore, the Article title contained an error in the capitalisation of 'Stone Age'. Both of these errors have now been corrected in both the PDF and HTML versions of the Article.

The palaeoecological context of the Oldowan-Acheulean in southern Africa.

The influence of climatic and environmental change on human evolution in the Pleistocene epoch is understood largely from extensive East African stable isotope records. These records show increasing proportions of C4 plants in the Early Pleistocene. We know far less about the expansion of C4 grasses at higher latitudes, which were also occupied by early Homo but are more marginal for C4 plants. Here we show that both C3 and C4 grasses and prolonged wetlands remained major components of Early Pleistocene environments in the central interior of southern Africa, based on enamel stable carbon and oxygen isotope data and associated faunal abundance and phytolith evidence from the site of Wonderwerk Cave. Vegetation contexts associated with Oldowan and early Acheulean lithic industries, in which climate is driven by an interplay of regional rainfall seasonality together with global CO2 levels, develop along a regional distinct trajectory compared to eastern South Africa and East Africa.

78,000-year-old record of Middle and Later stone age innovation in an East African tropical forest.

The Middle to Later Stone Age transition in Africa has been debated as a significant shift in human technological, cultural, and cognitive evolution. However, the majority of research on this transition is currently focused on southern Africa due to a lack of long-term, stratified sites across much of the African continent. Here, we report a 78,000-year-long archeological record from Panga ya Saidi, a cave in the humid coastal forest of Kenya. Following a shift in toolkits ~67,000 years ago, novel symbolic and technological behaviors assemble in a non-unilinear manner. Against a backdrop of a persistent tropical forest-grassland ecotone, localized innovations better characterize the Late Pleistocene of this part of East Africa than alternative emphases on dramatic revolutions or migrations.

Persistent tropical foraging in the highlands of terminal Pleistocene/Holocene New Guinea.

The terminal Pleistocene/Holocene boundary (approximately 12-8 thousand years ago) represented a major ecological threshold for humans, both as a significant climate transition and due to the emergence of agriculture around this time. In the highlands of New Guinea, climatic and environmental changes across this period have been highlighted as potential drivers of one of the earliest domestication processes in the world. We present a terminal Pleistocene/Holocene palaeoenvironmental record (12-0 thousand years ago ) of carbon and oxygen isotopes in small mammal tooth enamel from the site of Kiowa. The results show that tropical highland forest and open mosaics, and the human subsistence focused on these environments, remained stable throughout the period in which agriculture emerged at nearby Kuk Swamp. This suggests the persistence of tropical forest foraging among highland New Guinea groups and highlights that agriculture in the region was not adopted as a unilinear or dramatic, forced event but was locally and historically contingent.

Fruits of the forest: Human stable isotope ecology and rainforest adaptations in Late Pleistocene and Holocene (∼36 to 3 ka) Sri Lanka.

Sri Lanka has yielded some of the earliest dated fossil evidence for Homo sapiens (∼38-35,000 cal. years BP [calibrated years before present]) in South Asia, within a region that is today covered by tropical rainforest. Archaeozoological and archaeobotanical evidence indicates that these hunter-gatherers exploited tropical forest resources, yet the contribution of these resources to their overall subsistence strategies has, as in other Late Pleistocene rainforest settings, remained relatively unexplored. We build on previous work in this tropical region by applying both bulk and sequential stable carbon and oxygen isotope analysis to human and faunal tooth enamel from the sites of Batadomba-lena, Fa Hien-lena, and Balangoda Kuragala. Tooth enamel preservation was assessed by means of Fourier Transform Infrared Spectroscopy. We use these data to produce a detailed stable isotope ecology for Late Pleistocene-Holocene foragers in Sri Lanka from ∼36-29,000 to 3000 cal. years BP, allowing us to test the degree of human tropical forest resource reliance over a considerable time period. Given that non-human primates dominate the mammalian assemblages at these sites, we also focus on the stable isotope composition of three monkey species in order to study their ecological preferences and, indirectly, human hunting strategies. The results confirm a strong human reliance on tropical forest resources from ∼36-29,000 cal. years BP until the Iron Age ∼3 cal. years BP, while sequential tooth data show that forest resources were exploited year-round. This strategy was maintained through periods of evident environmental change at the Last Glacial Maximum and upon the arrival of agriculture. Long-term tropical forest reliance was supported by the specialised capture of non-human primates, although the isotopic data revealed no evidence for niche distinction between the hunted species. We conclude that humans rapidly developed a specialisation in the exploitation of South Asia's tropical forests following their arrival in this region.

Stable carbon, oxygen, and nitrogen, isotope analysis of plants from a South Asian tropical forest: Implications for primatology.

Stable isotope analysis of primate tissues in tropical forest contexts is an increasingly popular means of obtaining information about niche distinctions among sympatric species, including preferences in feeding height, forest canopy density, plant parts, and trophism. However, issues of equifinality mean that feeding height, canopy density, as well as the plant parts and plant species consumed, may produce similar or confounding effects. With a few exceptions, researchers have so far relied largely on general principles and/or limited plant data from the study area as references for deducing the predominant drivers of primate isotope variation. Here, we explore variation in the stable carbon (δ13 C), nitrogen (δ15 N), and oxygen (δ18 O) isotope ratios of 288 plant samples identified as important to the three primate species from the Polonnaruwa Nature Sanctuary, Sri Lanka, relative to plant part, season, and canopy height. Our results show that plant part and height have the greatest effect on the δ13 C and δ18 O measurements of plants of immediate relevance to the primates, Macaca sinica, Semnopithecus priam thersites, and Trachypithecus vetulus, living in this monsoonal tropical forest. We find no influence of plant part, height or season on the δ15 N of measured plants. While the plant part effect is particularly pronounced in δ13 C between fruits and leaves, differential feeding height, and plant taxonomy influence plant δ13 C and δ18 O differences in addition to plant organ. Given that species composition in different regions and forest types will differ, the results urge caution in extrapolating general isotopic trends without substantial local baselines studies.

Tropical forests and the genus Homo.

Tropical forests constitute some of the most diverse and complex terrestrial ecosystems on the planet. From the Miocene onward, they have acted as a backdrop to the ongoing evolution of our closest living relatives, the great apes, and provided the cradle for the emergence of early hominins, who retained arboreal physiological adaptations at least into the Late Pliocene. There also now exists growing evidence, from the Late Pleistocene onward, for tool-assisted intensification of tropical forest occupation and resource extraction by our own species, Homo sapiens. However, between the Late Pliocene and Late Pleistocene there is an apparent gap in clear and convincing evidence for the use of tropical forests by hominins, including early members of our own genus. In discussions of Late Pliocene and Early Pleistocene hominin evolution, including the emergence and later expansion of Homo species across the globe, tropical forest adaptations tend to be eclipsed by open, savanna environments. Thus far, it is not clear whether this Early-Middle Pleistocene lacuna in Homo-rainforest interaction is real and representative of an adaptive shift with the emergence of our species or if it is simply reflective of preservation bias.

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.

Protein sequences bound to mineral surfaces persist into deep time.

Proteins persist longer in the fossil record than DNA, but the longevity, survival mechanisms and substrates remain contested. Here, we demonstrate the role of mineral binding in preserving the protein sequence in ostrich (Struthionidae) eggshell, including from the palaeontological sites of Laetoli (3.8 Ma) and Olduvai Gorge (1.3 Ma) in Tanzania. By tracking protein diagenesis back in time we find consistent patterns of preservation, demonstrating authenticity of the surviving sequences. Molecular dynamics simulations of struthiocalcin-1 and -2, the dominant proteins within the eggshell, reveal that distinct domains bind to the mineral surface. It is the domain with the strongest calculated binding energy to the calcite surface that is selectively preserved. Thermal age calculations demonstrate that the Laetoli and Olduvai peptides are 50 times older than any previously authenticated sequence (equivalent to ~16 Ma at a constant 10°C).