Prof Christopher Ramsey

Abstract:

Radiocarbon (14C) provides the most frequently used approach to dating the last 55 000 years. However, owing to fluctuations in past levels of 14C, all radiocarbon dating requires calibration to convert the 14C measurement obtained from a sample into a calendar age. This is achieved by comparing the sample's 14C determination against a suitable calibration curve constructed from 14C measurements of reference samples that have known, or independently estimated, calendar age. The internationally agreed standards for these 14C calibration curves are provided by the IntCal working group, which ensures comparability between derived chronologies. The IntCal curves are periodically updated as significant new reference 14C datasets and Earth system insights become available. Since the last IntCal update in 2020, we have seen a substantial increase in the volume of reference 14C datasets available for use in calibration curve construction, in particular, measurements of annual growth rings in trees that represent individual calendar years. The rapid increase in reference 14C datasets provides exciting new opportunities for the radiocarbon community, but also presents challenges to ensure that 14C calibration remains reliable and accurate for all users. In this paper, we present some of these challenges and opportunities, and discuss some of the ideas under consideration for the next set of IntCal curve updates, which are planned to be released within the next year. This article is part of the Theo Murphy meeting issue 'Radiocarbon and cosmic radiation events'.

Abstract:

ABSTRACT There is now a wealth of glass‐shard geochemical data for volcanic ash (tephra) layers from a wide range of volcanoes and eruptions, providing invaluable datasets for tephrochronology. However, compilation of published data to assess tephra correlations leads to large files and requires careful management. Here, we show that a project within the IntChron Integration Tool (Ramsey et al., 2019), an open‐access and versatile online application, can be used to effectively store and manage tephra information, geochemical data and relevant metadata, while also providing visualisation and statistical tools. The visualisation functionality allows sites to be plotted on a variety of base maps, enables the plotting of tephra shard concentrations through a sequence and generates biplots of major and trace elements. The statistical tools are similarly invaluable for investigating compositional variability and relationships, and for assessing the probability that datasets correlate. An IntChron Integration Tool project supports the entire workflow, from sample and data collection through analysis and interpretation, to the generation of publication‐ready plots. Here, we present an example project to show the functionality using published data from distal tephra layers in the Lake Suigetsu core, and proximal eruption deposits from volcanoes across Japan. This project contains over 7000 geochemical analyses from 12 publications, demonstrating the power of the IntChron Integration Tool to manage, visualise and archive geochemical datasets.

Abstract:

Plague is among the most devastating diseases in human history1. However, early strains of the plague-causing bacterium Yersinia pestis lacked virulence factors that are required for the bubonic form until around 3,800 years ago2, 3. Consequently, the morbidity and mortality of early plague strains remain unclear. Here we describe early plague strains that are associated with two phases of outbreaks among mid-Holocene hunter-gatherers near Lake Baikal in southeast Siberia, beginning from about 5,500 years ago. These outbreaks occur across four hunter-gatherer cemeteries, with a 39% detection rate for plague infection. By reconstructing kinship pedigrees, we show that small familial groups were affected, consistent with human-to-human spread of disease, and that the first outbreak occurred within a single generation. The infections appear to have resulted in acute mortality, especially among children (aged 8 to 11 years). We further note functional differences, including in the ypm superantigen locus, which is also present in present day Yersinia pseudotuberculosis. The new strains diverge ancestrally to known Y. pestis and constrain the timing of its emergence, indicating that this happened before approximately 5,700 years ago. These findings show that plague outbreaks happened earlier than previously thought and were indeed lethal. We contend that the occurrence of outbreaks among mid-Holocene hunter-gatherer communities well outside the sphere of Late Neolithic Europe challenges the notion that higher population densities and lifestyle changes during the Neolithic agricultural transition were prerequisites for plague epidemics.

Abstract:

Radiocarbon dating is essential for establishing robust chronologies in archaeological and paleoenvironmental contexts spanning the last 55,000 years. Pottery, pervasive in the archaeological record, offers a crucial framework for dating human activity during the Holocene. Traditionally, radiocarbon dating of pottery has relied on targeting carbonaceous inclusions such as organic temper or measuring stratigraphically associated materials like bone and charcoal. Inaccuracies can arise, however, if the targeted fraction does not reflect the timing of vessel use or if stratigraphic associations are uncertain. An alternative involves radiocarbon dating of lipid residues, particularly fatty acids absorbed into the ceramic matrix during the processing and storage of plant and animal-derived resources. This approach holds promise for delivering highly accurate measurements directly correlating to vessel use. At the Oxford Radiocarbon Accelerator Unit, efforts have been made to develop this methodology through compound-specific radiocarbon dating of pottery, employing a gas chromatography (GC)-preparative fraction collector (PFC) approach. Here, we describe the protocol and present preliminary findings, including analyses conducted on pottery samples sourced from an archaeological site with an established chronology.

Abstract:

Narratives about the motivations and conditions for mass violence as a persistent feature of conflict throughout human history have evolved in complexity and materiality. Victims of these events are key for understanding the evolution and transformative power of violent behaviour as it developed from simple intergroup conflict to more strategic mass violence. Here we present the results of a bioarchaeological study of 77 and biomolecular analysis of 25 individuals from a ninth-century BCE mass grave from Gomolava in the Carpathian Basin, Southeast Europe. The site is located at the interface of complex sociospatial relations, divergent cultural traditions and values, and competing ideologies of landscape use. We show that excessive lethal violence enacted mostly on women and children suggests a selective demographic bias. The people buried together shared few, even distant, genetic relationships, and so their killing presents striking evidence for an episode of cross-regional conflict and an underlying aggressive shift in power, violence and gender relations in the region. Gomolava provides evidence consistent with deliberate annihilation of select sections of a regional population as a motivation for mass violence behaviour in later prehistoric Europe. It also shines new light on the socioeconomic agency and importance of women and young individuals in later European prehistory.