The morphological variability of Maltese ‘cart ruts’ and its implications

Hundreds of ‘cart ruts’ – pairs of incised parallel grooves in the bedrock – are found across the Maltese archipelago in the central Mediterranean. The age, functional association, formation processes, and taphonomic alteration of these ruts, which occur here with a globally unrivalled frequency, has been much debated. Generally seen as being created by erosion from vehicles such as wheeled carts, or alternatively being cut into the rock to facilitate movement of such vehicles, specific models range from the use of carts to move soil in the Neolithic to them reflecting classical era stone quarrying, and many other possibilities. One interesting aspect concerns the morphological variability of the cart ruts, such as the notion that they have a standard gauge (width between ruts), and that this gauge is very similar to that of modern railway tracks. Evaluating the morphological variability of the cart ruts contributes to an understanding of the phenomenon, as, for instance, we might expect that if they date to different periods, with different functions, and/or were extensively modified by geomorphological processes this will be reflected in the character of their morphological variability. The analysis suggests that cart ruts are fairly standardised in terms of basic measurements such as widths and depth, perhaps suggesting that they are of a consistent age and function. This study identified a need for definitional clarity as the commonly cited gauge measurements are not taken in the same way as gauge is defined for railway tracks. There are hints of rut shape changes reflecting extensive use and or processes such as limestone dissolution, which give insights into their formation histories.1. Introduction 1.1. Background and context 1.2. Previous work on cart-rut morphology 2. Methods 3. Results 3.1. General remarks 3.2. Relationships between morphological features 4. Discussio

Maltese chert: an archaeological perspective on raw material and lithic technology in the central Mediterranean

The Maltese islands are renowned for their prehistoric archaeological record, articularly the famous megalithic ‘temples’ and associated ceramics and artwork. The temples were built by a society lacking metal technology, who relied on stone and organic materials. Knapped stone tool (lithic) technology, to produce sharp edged tools for tasks like cutting, hide working, and wood shaping involved the use of both imported obsidian and high-quality chert – offering insights into themes of exchange and connectivity – and local chert. The local chert has generally been described as low-quality, yet relatively little research has been conducted on its distribution, characteristics, and use. In this paper I report a survey of chert sources, identifying a wider distribution of chert outcrops along the west coast of Malta than previously discussed. Some general macroscopic properties are outlined, while there are also aspects of variability in the chert sources. Knapping experiments were then conducted on samples of chert collected, allowing clarification of its characteristics. These observations are used to offer some insights into lithic technology in Neolithic and Temple Period Malta, such as the hypothesis that the high frequencies of multidirectional flake production and subsequent ‘scraper retouch’ reflect adaptations to the characteristics of local chert.Introduction Maltese lithic technology Maltese chert geology and geochemistry Methods Description of chert sources Knapping experiments Discussion and conclusio

Sum things are not what they seem: Problems with point-wise interpretations and quantitative analyses of proxies based on aggregated radiocarbon dates

Radiocarbon-date assemblages are commonly used as proxies for past human and environmental phenomena. Prominent examples of target phenomena include past population levels and sea level fluctuations. These processes are thought to have affected the amount of organic carbon deposited into the archaeological and/or palaeoenvironmental record. Time-series representing through-time fluctuations in the frequency of radiocarbon samples are, therefore, often used as proxies for such processes. However, there are critical problems with using radiocarbon ?dates-as-data? in point-wise comparisons and these problems have gone largely underappreciated. The key problem is that the established proxies are easily misinterpreted. They conflate process variation and chronological uncertainty, which makes them unsuitable for point-wise comparisons aimed at identifying rates of change, comparing variables directly, or estimating parameters in regression models. Here we explore the interpretive and analytical problems in detail in an effort to raise awareness and promote skepticism about the use of the established proxies in point-wise comparisons. We also provide suggestions for future research and point to potential methodological alternatives that may improve the viability of dates-as-data approaches.Introduction Interpreting proxies based on aggregated radiocarbon dates - SPDF - Average KDE models Discussion - Analytical problems for point-wise approaches - Implications - Directions for future work Conclusio

Extreme events in biological, societal, and earth sciences: A systematic review of the literature

The term “extreme event” is commonly used to describe high-impact, unanticipated natural events, like floods, tsunamis, earthquakes, and volcanic eruptions. It first appeared in the scientific literature in the 1950s and has since spread to disciplines as diverse as economics, psychology, medicine, and engineering. The term is increasingly being applied to the study of historical, prehistorical, and deep-time events across a broad range of scales, and it is widely acknowledged that such events have had profound impacts on the Earth’s biodiversity and cultures. Understandably, then, how people think about, define, and study extreme events varies considerably. With extreme events expected to become more frequent, longer lasting, and more intense in the coming decades as a result of global warming, the differing extreme event definitions—both across and within disciplines—is likely to lead to confusion among researchers and pose significant challenges for predicting and preparing for extreme events and their impacts on natural and social systems. With this in mind, we conducted a systematic quantitative review of 200 randomly selected, peer-reviewed “extreme event” research papers (sourced from Web of Science, accessed January 2020) from the biological, societal, and earth sciences literature with the aim of quantifying several pertinent features of the research sample. On the one hand, our analysis found a great deal of variability among extreme event papers with respect to research interests, themes, concepts, and definitions. On the other hand, we found a number of key similarities in how researchers think about and study extreme events. One similarity we encountered was that researchers tend to view extreme events within a particular temporal context and quite often in terms of rates of change. Another similarity we encountered was that researchers often think of and study extreme events in terms of risks, vulnerabilities, and impacts. The similarities identified here may be useful in developing a common and comprehensive definition of what constitutes an extreme event, and should allow for more comparative research into extreme events at all spatio-temporal scales which, we predict, will provide important new insights into the nature of extreme events.Introduction Materials and methods Results - Sampling adequacy - Summary of the literature Discussion - Defining and conceptualizing extreme events - Thematic clusters in the literature -- Health, vulnerability, and risk -- Human-environment interactions -- Human health and well-being -- Climate change dynamics - Consilience - Future directions - Study limitations Conclusio

Uniformity and Diversity in Handaxe Shape at the End of the Acheulean in Southwest Asia

This study examines parameters, causes, and spatio-temporal patterns of handaxe shape variation from Tabun cave in the Levant, and Khall Amayshan 4B and Khabb Musayyib in northern Arabia. These assemblages span the range of most pointy to most rounded handaxes found anywhere during the Acheulean. The AGMT3D program is used to conduct high resolution geometric morphometric analysis of handaxe form from 3D models. Shape variation is tested against blank type, allometry, and reduction intensity. None of these factors appears to be a strong influence, but there are significant assemblage-wise differences in form, suggesting the different shapes were intentionally produced. The analysis quantifies a pattern of high diversity in the assemblages from Tabun versus low diversity in the shorter occupations at the Arabian sites. We suggest possible explanations of emerging specificity in utilitarian functions, as well as the manifestation of social identities in artefacts at the end of the Acheulean

Human occupation of the northern Arabian interior during early Marine Isotope Stage 3

The early part of Marine Isotope Stage (MIS) 3 (ca. 60–50 ka) is a crucial period for studying human demography and behaviour in south-west Asia, and how these relate to climatic changes. However, the archaeological and palaeoenvironmental records for MIS 3 in critical areas such as the Arabian Peninsula remain poorly developed. Here, we present findings from the Al Marrat basin in the Nefud desert, which provides the first clear evidence for both increased humidity and human occupation of the interior of northern Arabia during early MIS 3. A Middle Palaeolithic assemblage, dated by optically stimulated luminescence to ca. 55 ka, was found stratified within a sequence of relict palustrine deposits indicative of shallow water body formation in the Al Marrat basin. Hominin presence in northern Arabia at this time coincides with the intensification and northward displacement of monsoon rainfall systems during a period of maximum insolation. These findings add to a growing corpus of palaeoenvironmental evidence, which indicates that the Arabian interior was neither arid nor unpopulated during early MIS 3, and that hydrodynamic responses to enhanced moisture availability facilitated demographic expansions into the Arabian interior

Orbital-scale climate variability in Arabia as a potential motor for human dispersals

The Arabian Peninsula is situated at an important crossroads for the movement of Pleistocene human populations out of, and into, Africa. Although the timings, routes and frequencies of such dispersals have not yet been confirmed by genetic, fossil or archaeological evidence, expansion into Arabia would have been facilitated by humid periods driven by incursions of monsoon rainfall, potentially from both Indian Ocean and African monsoon systems. Here we synthesise terrestrial and marine core palaeoclimatic data in order to establish the spatial and temporal variability of humid periods in Arabia between late Marine Isotope Stage (MIS) 7 and 3. Incursions of monsoon rainfall occurred during periods of insolation maxima at ca. 200–190, 170, 155, 130–120, 105–95, 85–75 and 60–55 ka, providing multiple ‘windows’ of favourable climatic conditions that could have facilitated demographic expansion through Arabia. Strong summer monsoons are generally associated with mid-high latitude interglacials, however, enhanced monsoon convection also brought rainfall into Arabia during global glacial phases, possibly due to a strengthened winter monsoon and a greater influence of southern hemispheric temperature changes. Key periods for dispersal into northern regions of Arabia correspond with the synchronous intensification of both eastern Mediterranean and monsoon rainfall systems at insolation maxima during MIS 7 and MIS 5, which may have facilitated demographic connectivity between the Levant and the Arabian interior. Environmental conditions throughout southern and southeast regions were also favourable to expansion during these times, although strong monsoons in these regions during MIS 6 and MIS 3 suggest further opportunities for demographic expansion and exchange. Terrestrial and marine evidence show that during early MIS 3 (ca. 60–50 ka), a strengthened monsoon led to the activation of interior drainage systems and increased productivity in coastal zones, indicating that favourable environmental conditions existed along both coastal and interior routes at that time

Alluvial fan records from southeast Arabia reveal multiple windows for human dispersal

The dispersal of human populations out of Africa into Arabia was most likely linked to episodes of climatic amelioration, when increased monsoon rainfall led to the activation of drainage systems, improved freshwater availability, and the development of regional vegetation. Here we present the first dated terrestrial record from southeast Arabia that provides evidence for increased rainfall and the expansion of vegetation during both glacial and interglacial periods. Findings from extensive alluvial fan deposits indicate that drainage system activation occurred during Marine Isotope Stage (MIS) 6 (ca. 160–150 ka), MIS 5 (ca. 130–75 ka), and during early MIS 3 (ca. 55 ka). The development of active freshwater systems during these periods corresponds with monsoon intensity increases during insolation maxima, suggesting that humid periods in Arabia were not confined to eccentricity-paced deglaciations, and providing paleoenvironmental support for multiple windows of opportunity for dispersal out of Africa during the late Pleistocene