The Saharo-Arabian Desert is one of the largest biogeographical barriers on Earth, impeding dispersals between Africa and Eurasia, including movements of past hominins. Recent research suggests that this barrier has been in place since at least 11 million years ago 1 . In contrast, fossil evidence from the late Miocene epoch and the Pleistocene epoch suggests the episodic presence within the Saharo-Arabian Desert interior of water-dependent fauna (for example, crocodiles, equids, hippopotamids and proboscideans) 2–6 , sustained by rivers and lakes 7,8 that are largely absent from today’s arid landscape. Although numerous humid phases occurred in southern Arabia during the past 1.1 million years 9 , little is known about Arabia’s palaeoclimate before this time. Here, based on a climatic record from desert speleothems, we show recurrent humid intervals in the central Arabian interior over the past 8 million years. Precipitation during humid intervals decreased and became more variable over time, as the monsoon’s influence weakened, coinciding with enhanced Northern Hemisphere polar ice cover during the Pleistocene. Wetter conditions likely facilitated mammalian dispersals between Africa and Eurasia, with Arabia acting as a key crossroads for continental-scale biogeographic exchanges.

ABSTRACT Analysis of plant‐wax biomarkers from sedimentary sequences can enable past environmental and hydrological reconstruction and provide insights into past hominin adaptations. However, biomarker preservation in desert contexts has been considered unlikely given the sparse nature of the vegetation within the landscape. Here we evaluate the preservation of n ‐alkanes and fatty acids collected from four depositional sequences associated with archaeological contexts in the Nefud Desert, Saudi Arabia, and the Thar Desert, India. Pleistocene and Holocene samples were selected to understand the effects of age on preservation. The results of molecular distribution patterns and indices, particularly the high carbon preference index and average chain length, show the preservation of plant‐wax biomarkers in both the Holocene and Pleistocene desert sequences, while δ 13 C values and organic content provide insights into the vegetation contributing to the plant‐wax organic pool. This study provides a baseline for understanding human–environment interactions and for reconstructing changes in arid land habitats of relevance to hominins during the Quaternary.

Recent advances in interdisciplinary archaeological research in Arabia have focused on the evolution and historical development of regional human populations as well as the diverse patterns of cultural change, migration, and adaptations to environmental fluctuations. Obtaining a comprehensive understanding of cultural developments such as the emergence and lifeways of Neolithic groups has been hindered by the limited preservation of stratified archaeological assemblages and organic remains, a common challenge in arid environments. Underground settings like caves and lava tubes, which are prevalent in Arabia but which have seen limited scientific exploration, offer promising opportunities for addressing these issues. Here, we report on an archaeological excavation and a related survey at and around Umm Jirsan lava tube in the Harrat Khaybar, north-western Saudi Arabia. Our results reveal repeated phases of human occupation of the site ranging from at least the Neolithic through to the Chalcolithic/Bronze Age. Pastoralist use of the lava tube and surrounding landscape is attested in rock art and faunal records, suggesting that Umm Jirsan was situated along a pastoral route linking key oases. Isotopic data indicates that herbivores primarily grazed on wild grasses and shrubs rather than being provided with fodder, while humans had a diet consistently high in protein but with increasing consumption of C3 plants through-time, perhaps related to the emergence of oasis agriculture. While underground and naturally sheltered localities are globally prominent in archaeology and Quaternary science, our work represents the first such combined records for Saudi Arabia and highlight the potential for interdisciplinary studies in caves and lava tubes.

Monumental rectangular stone structures called mustatils are an important emerging feature of the Holocene archaeological record of northwestern Arabia. To date, few have been excavated, with available radiocarbon dates suggesting an age range of ca. 5400–4200 BC. Here we present a rigorous spatial analysis to identify the patterning and landscape context of 169 mustatils in the southern and western margins of the Nefud Desert. This included: (1) a systematic survey of satellite imagery to identify mustatils; (2) viewshed analysis to examine location and landscape visibility; (3) a point process model to understand how diverse environmental and landscape variables affect mustatil locations; (4) mark correlation function to assess spatial patterning of mustatils based on their size. Results indicate that mustatil locations are determined most by proximity to water (likely locations of enhanced surface water occurrence under the enhanced humidity of the Mid-Holocene), on east facing slopes, close to rocky areas, at elevations between 880 and 950 masl, and on or near topographic ridges (positive topographic position index). Viewshed analysis showed that mustatils are preferentially located in areas that have good views, but not the best that are available, indicating complex landscape positioning that balances a range of topographic and behavioural factors. Using a rank permutation method with size (length) of mustatils as a proxy for labour mobilization we show that mustatils within clusters are not arranged hierarchically based on size, and were likely built by non-stratified groups of people. Our analyses show that people were choosing multiple factors when deciding where to build mustatils, and that the distribution of mustatils may relate to different groups of people resulting in the construction of complex ritual landscapes. As one of the earliest examples of large-scale monumental stone structure construction in global prehistory, understanding mustatils can enlighten us on human-environment interaction during the Neolithic.

The Neolithic of northern Arabia is characterised by monumental stone structures, ephemeral 'hearth sites' indicative of a highly mobile lifestyle, and a rich rock art heritage with iconic representations of domesticated livestock. However, the character and timing of occupation prior to the spread of pastoralism (ca. 6000 BCE) remains elusive, with only one stratified Epipalaeolithic site and two surface early Neolithic sites so-far known in the Jubbah Oasis. Here we present Sahout, a newly documented rock art site with Neolithic and earlier occupations, on the southern edge of the Nefud desert. The rock art is dominated by life-sized, naturalistic, engravings of camels, which are in some cases superimposed with Neolithic imagery of domesticated sheep. Surveys and test excavations carried out in the vicinity of the rock art revealed a lithic assemblage with similarities to the late Epipalaeolithic and Pre-Pottery Neolithic of the Levant. Radiocarbon ages from two test trenches and two hearths indicate repeated occupation at Sahout between the Terminal Pleistocene and the Middle Holocene, which partly mirror the rock art sequence. Investigations at Sahout indicate that rock art production in northern Arabia may have begun earlier than previously thought. Research also suggests a broader geographical extent to human occupations prior to the Holocene humid period.

Archaeological sites with surface hearths are a ubiquitous feature across the arid zones of the Arabian interior. At Jebel Oraf, in the Jubbah basin of the Nefud Desert of northern Arabia, numerous grinding stone fragments were found in association with hearths, though the original purpose of these stones was unclear owing to the poor preservation of faunal and botanic remains. Here we describe results from use-wear analysis on five grinding tools at Jebel Oraf, demonstrating that such artefacts were used during the Neolithic for plant processing, bone processing, and pigment production. Grinding stones were often broken up after initial use and fragments were subsequently re-used for alternative purposes, before finally being placed on hearths or discarded. More specifically, plants were ground or prepared and possibly cooked in the hearths, and bones were processed as well. The analyses also highlight the importance of pigment processing at Neolithic sites and provide a link to painted rock art. The frequent use of pigment in the archaeological record suggests that pigment was widely used, and that Neolithic painted art may have been more common than the surviving images suggest.

Past environmental and climatic conditions within the Arabian Peninsula are key to understanding the setting for hominin dispersal across the Saharo-Arabian dryland belt. The tufa deposits within the volcanic harrats on the southwest coast of Saudi Arabia fill a significant spatial gap in the distribution of palaeoenvironmental records on the west coast of the Arabian Peninsula adjacent to the Red Sea. In the catchment of Wadi Dabsa in the Harrat Al Birk, there are widespread fossil palustrine to shallow-lacustrine tufa deposits with fluvial elements. Several phases of tufa accumulation, separated by fluvial downcutting, are observable within these powerful palaeoenvironmental proxies. U–Th dating of targeted dense, banded tufa facies, yield ages that are stratigraphically consistent at the landscape scale, and indicate that tufa accumulation occurred during distinct humid phases broadly coeval with the last two warm interglacial Marine Isotope Stages (MIS 7 and MIS 5). For the first time this shows humid intervals in southwest Arabia coincident with the southern coast. There is a simlar pattern emerging further north in the Arabian Peninsula, The Sinai and Levant and further on into continental Europe. Furthermore, tufa δ18O ranges from −14.6 to −1.9‰, covering a range similar to those reported for tufa from north African oasis sites and speleothems elsewhere on the Arabian Peninsula and The Levant. The lowest δ18O values are derived from MIS 5e samples, a pattern in agreement with speleothems in Yemen and Oman, and consistent with an isotopic-enabled climate model simulation for this time slice. The δ13C and Sr isotopic compositions of dated tufa samples indicate deposition from shallow-circulating meteoric water, with no geothermal influence. This, along with the δ18O values, suggest a freshwater supply that was a potable water source in this landscape. The δ13C signatures at Wadi Dabsa are more negative than for parts of north Africa, suggesting Wadi Dabsa may have experienced comparatively higher biomass, thicker soils and wetter conditions with lower evaporative losses. This new record of tufa deposition during the middle and late Pleistocene, suggests for the first time that the west coast of Arabia experienced a similar history of humid phases over the past 250 ka as southern Arabia and the Nefud in the northern interior. These regional changes in hydroclimatic regime occur at timescales coincident with hominin dispersals.

The Camel Site is in the north of Saudi Arabia in the province of al-Jawf. It is characterised by three decaying sandstone hillocks with life-sized 3D engravings (or reliefs) of camels and equids likely carved during later prehistory. A survey in the central area of the site identified clusters of flakes and other flintknapping remains in the lower areas between the sandstone spurs and larger silcrete tools directly underneath the animal depictions. Some of these tools presented abraded edges, possibly from prolonged contact with the soft and abrasive sandstone that constitutes the rock spurs where the animals were carved. Experiments were performed to test this hypothesis and have a reference collection for further traceological analysis. The chaine opératoire of the experimental engraving tools, from raw material procurement, tool manufacture and use, reuse and discard, was conducted with locally available materials comparable to the archaeological specimens. Specific experimental variables, including how the force was applied, in what direction the movement took place and the orientation of the stone tool during the experiment, were also recorded. Macro- and microscopic analyses of the experimental collection and a sample of archaeological artefacts seem to show that the ancient tools found on the surface were probably used to make the camelid and equid reliefs at the site.

Among the rock art in Arabia, a little-known Neolithic tradition of large, naturalistic camel depictions stands out. Their geographic distribution and stylistic traits suggest close links with the Camel Site reliefs. Four newly documented panels appear to have been carved by the same individual (or group), tracing repeated movements over hundreds of kilometres.

Archaeologists have long emphasized the importance of large-scale excavations and multi-year or even decades-long projects at a single site or site complex. Here, we highlight archaeological field strategies, termed coring, profiling, and trenching (CPT), that rely on relatively small-scale excavations or the collection of new samples from intact deposits in previously excavated trenches (aka test units or pits). Examples from multiple sites in Africa, Asia, and North America demonstrate that CPT is highly effective for obtaining high-resolution archaeobiological and geoarchaeological samples (e.g., faunal and botanical remains, sediments) and artefacts from areas that have seen limited or no archaeological research, little systematic application of archaeological science methods, or research only on a relatively narrow time period or geographic scale. Designed to complement large-scale excavations at single sites, CPT is ideal for multi-scalar research that works in tandem with remote sensing techniques, providing samples for detailed laboratory analyses and offering a bridge between surface surveys and large-scale excavation. Given the threats facing archaeological sites around the world from climate change and human development, as well as financial, training and infrastructure constraints, and concerns from many Indigenous communities about large excavations, we argue that CPT is an important method for addressing 21st century human-environmental research questions.

The life-sized, naturalistic reliefs at the Camel Site in northern Arabia have been severely damaged by erosion. This, coupled with substantial destruction of the surrounding archaeological landscape, has made a chronological assessment of the site difficult. To overcome these problems, we combined results from a wide range of methods, including analysis of surviving tool marks, assessment of weathering and erosion patterns, portable X-ray fluorescence spectrometry, and luminescence dating of fallen fragments. In addition, test excavations identified a homogenous lithic assemblage and faunal remains that were sampled for radiocarbon dating. Our results show that the reliefs were carved with stone tools and that the creation of the reliefs, as well as the main period of activity at the site, date to the Neolithic. Neolithic arrowheads and radiocarbon dates attest occupation between 5200 and 5600 BCE. This is consistent with measurements of the areal density of manganese and iron in the rock varnish. The site was likely in use over a longer period and reliefs were re-worked when erosion began to obscure detailed features. By 1000 BCE, erosion was advanced enough to cause first panels to fall, in a process that continues until today. The Camel Site is likely home to the oldest surviving large-scale (naturalistic) animal reliefs in the world.

A series of uncharacterised tufa deposits within the lowland volcanic provinces of western Saudi Arabia are investigated here in order to account for their presence and to examine their utility as a palaeoenvironmental archive. The Wadi Dabsa basin, in the Harrat Al Birk, is part of the Saharo-Arabian region, where there is increasing evidence for multiple hominin dispersals during windows of reduced aridity during the last ~400 ka of the Late Quaternary. This first and detailed petrological and geochemical characterisation of these tufa carbonates is particularly important for palaeoenvironmental and climatological reconstruction at a site that contains a major concentration of Early and Middle Stone Age artefacts. We aim to determine the nature of deposition, to answer whether these are cool, freshwater tufa or hydrothermal travertine, and to establish what the tufa settings, stratigraphies and facies reveal about the hydroclimatic regime in this semi-arid environment. A widespread lacustrine-paludal and fluvial tufa system is preserved, as well as topographically-controlled tufa barrages and cascades. Observable sections, exposed by incision, reveal a thickness of tufa deposits of 3 to 6 m in places, which contain two packages of tufa-cemented conglomerate facies. This allows us to provide a conceptual model for the deposition of semi-arid tufa, based on existing type sites in the Naukluft Mountains of Namibia and the Ebro Basin of Spain. The varied topography within this volcanic harrat provides a setting at Wadi Dabsa that combines the low-lying lacustrine-paludal model from Spain with the steeper and higher-energy model from Namibia. The two tufa-cemented bedload units and the evidence for post-depositional erosion of other tufa facies indicates a shifting hydroclimatic regime, with episodes during which the basin contained water and there was steady flow in the fluvial channels, alternating with episodes of high-energy flashy flows. Geochemical analysis using Sr-87/Sr-86 isotopic ratios (0.7049 to 0.7056 with one sample at 0.7062) and stable carbon isotopes (-12.9 to-6.3 parts per thousand) reveal that these are cool-water tufas were deposited from meteoric water that has interacted with both metamorphosed limestone in the Asir Escarpment and the mafic metavolcanic bedrock of the Wadi Dabsa Basin, without a geothermal influence. These tufa are low-concentration-magnesium calcite, with traces of quartz (to a maximum of 3%) and other silicates. Some samples have <= 7.5% palygorskite, which along with petrological evidence for microbial filaments suggests the importance of biomineralisation by cyanobacteria within some of these tufa. Petrological analysis shows the fabrics are dominated by micrite cements with some microspar, and very little post-depositional alteration. Where samples are banded, this reflects variation in calcite crystal size as opposed to any striking variations in mineralogical composition. Oxygen stable isotopic composition (-14.6 to-1.9 parts per thousand) indicates deposition from an isotopically more depleted rainfall source than the modern day, noting additional corrections for unknown past temperature and any other fractionation effects are needed. Depleted rainfall sources in this region may relate to either a far-travelled Atlantic moisture source or a higher-intensity Indian Ocean monsoon source, or some combination. (C) 2022 Elsevier B.V. All rights reserved.

Between the Levant and the Indian sub-continent only a few Acheulean sites have been documented, hampering models of hominin dispersals. Here we describe the first Acheulean sites to be discovered in the Nefud Desert of northern Arabia. The four sites occur in a variety of settings including adjacent to an alluvial fan drainage system, at a knappable stone source, and on the margins of endorheic basins. We discuss the implications of the sites for hominin landscape use, in particular the preferential transport and curation of bifaces to fresh water sources. The bifaces correspond to the Large Flake middle Acheulean in the Levantine sequence. The sites occupy a gap in the distribution of the Acheulean across the Saharo-Arabian arid belt, and as such have implications for dispersal routes between Africa and Asia.

We investigated the rock art (petroglyphs) in the Al-Quwaiyah Governorate (Saudi Arabia) with focus on the Musayqira site. Iconographic analysis showed a broad variety of human depictions, game animals (ibex, ass, ostrich, lion, etc.), domestic animals (cattle, camel, horse, dog, etc.), inscriptions and abstract symbols. Archaeometric measurements by pXRF provided the areal densities of Mn on petroglyphs and intact rock varnish. Varnish accumulation rates were derived from Mn density measurements on inscriptions of known approximate age. Applying these rates to varnish densities on the petroglyphs yielded age estimates. Some of the rock art was incised in fracture fill rather than true varnish, complicating the interpretation of the data. The combination of iconographic and archaeometric data indicated multiple phases of rock art creation, corresponding to the Late Neolithic, Bronze Age, Iron Age, and Islamic Period, with different artistic traditions, reflecting changing socioeconomic and ecological conditions.

Pleistocene hominin dispersals out of, and back into, Africa necessarily involved traversing the diverse and often challenging environments of Southwest Asia1-4. Archaeological and palaeontological records from the Levantine woodland zone document major biological and cultural shifts, such as alternating occupations by Homo sapiens and Neanderthals. However, Late Quaternary cultural, biological and environmental records from the vast arid zone that constitutes most of Southwest Asia remain scarce, limiting regional-scale insights into changes in hominin demography and behaviour1,2,5. Here we report a series of dated palaeolake sequences, associated with stone tool assemblages and vertebrate fossils, from the Khall Amayshan 4 and Jubbah basins in the Nefud Desert. These findings, including the oldest dated hominin occupations in Arabia, reveal at least five hominin expansions into the Arabian interior, coinciding with brief 'green' windows of reduced aridity approximately 400, 300, 200, 130-75 and 55 thousand years ago. Each occupation phase is characterized by a distinct form of material culture, indicating colonization by diverse hominin groups, and a lack of long-term Southwest Asian population continuity. Within a general pattern of African and Eurasian hominin groups being separated by Pleistocene Saharo-Arabian aridity, our findings reveal the tempo and character of climatically modulated windows for dispersal and admixture.

Hearth sites are characteristic of Holocene occupation in the Arabian sand seas but remain mostly unstudied. Excavations of two multi-period hearth sites in the Jebel Oraf palaeolake basin, in the oasis of Jubbah, now substantially increase our knowledge of these sites. In total, 17 of 170 identified hearths were excavated at Jebel Oraf 2 (ORF2), an open-air site on the edge of a palaeolake. In addition, 11 hearths were excavated at the stratified site of Jebel Oraf 115 (ORF115), a rockshelter formed by two boulders. Radiocarbon dating and lithic assemblages indicate that the majority of these hearths were in use in the second half of the 6th millennium BCE, and that both sites were used sporadically until the recent past. All hearths appear to have been extremely shortlived, and faunal remains suggest they may have been used to cook meat from hunted or trapped wildlife, and occasionally from livestock. The frequent use of grinding stones, often broken into fragments and used to cover hearths is also attested. Evidence for the exceptionally early use of metal from dated occupation deposits as well as from rock art, shows that these short-lived sites were well connected to technological innovations in the wider region.