Eleanor Scerri

The past half century has seen a move from a multiregionalist view of human origins to widespread acceptance that modern humans emerged in Africa. Here the authors argue that a simple out-of-Africa model is also outdated, and that the current state of the evidence favours a structured African metapopulation model of human origins. F or decades, polarized debates about human origins have swung between two major models. Classic multiregionalism viewed the majority of our ancestry as being spread across the Old World over the past one to two million years, and emphasized regional continuity. The recent and simple out-of-Africa (SOA) model proposed an expansion out of Africa in the past 100,000 yr from a single region in Africa. Testing these models has undoubtedly improved our understanding of recent human origins, but with ever-richer archaeological, anthropological, genetic and palaeoecological data available, are they still useful? We argue that these formulations now constrain progress in human evolutionary studies and call for a shift to structured metapopulation models.

The Acheulean is the longest lasting cultural–technological tradition in human evolutionary history. However, considerable gaps remain in understanding the chronology and geographical distribution of Acheulean hominins. We present the first chronometrically dated Acheulean site from the Arabian Peninsula, a vast and poorly known region that forms more than half of Southwest Asia. Results show that Acheulean hominin occupation expanded along hydrological networks into the heart of Arabia from Marine Isotope Stage (MIS) 7 until at least ~190 ka ̶ the youngest documented Acheulean in Southwest Asia. The site of Saffaqah features Acheulean technology, characterized by large flakes, handaxes and cleavers, similar to Acheulean assemblages in Africa. These findings reveal a climatically mediated later Acheulean expansion into a poorly known region, amplifying the documented diversity of Middle Pleistocene hominin behaviour across the Old World and elaborating the terminal archaic landscape encountered by our species as they dispersed out of Africa.

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.

The Levantine sites of Skhul and Qafzeh have been interpreted as indicating an early, short and unsuccessful expansion of Homo sapiens out of Africa. Chronometric age estimates, however, indicate a history of prolonged occupation, and suggest that Skhul (~130e100 thousand years ago [ka]) may have been occupied earlier than Qafzeh (beginning ~110e90 ka). Morphologically, the Skhul individuals can be described as somewhat more primitive in comparison to the Qafzeh fossils. Though the lithic assemblages of sites such as Skhul and Qafzeh are often described as being technologically similar, as part of the 'Tabun C' phase/industry, limited detailed information on the Skhul lithic assemblage has been published, and little comparative work has been conducted. Here, we present an analysis of the Skhul stone tool assemblage to describe its characteristics, to evaluate the lithic results against the fossil and chronological data, and for inter-site regional comparison. Our findings indicate that the Skhul lithic assemblage differs from other Levantine Marine Isotope Stage (MIS) 5 sites, such as Qafzeh. For example, there was more of an emphasis on diverse methods of point production at Skhul, and the available samples indicate a greater emphasis on preferential rather than recurrent Levallois reduction at Skhul. The current findings suggest that neither the Levantine Middle Palaeolithic in general, nor MIS 5 assemblages in particular, were technologically homogeneous. These data are consistent with either a long occupation of the Levant by Homo sapiens in MIS 5, or at least two phases of occupation (early MIS 5 and mid to late MIS). Whatever the fate of the Skhul and Qafzeh population(s), their occupation of the Levant was neither short nor culturally uniform. Our findings add to the growing pool of evidence that the dispersal of our species 'Out of Africa' was more complex than hitherto thought. Further work on MIS 5e contexts in the Levant and elsewhere in Southwest Asia should be a research priority.

Mid-latitude dune fields offer significant records of human occupations in southwest Asia, reflecting human responses to past climate changes. Currently arid, but episodically wetter in the past, the Nefud desert of northern Saudi Arabia provides numerous examples of human-environment interactions and population movements in the desert belt. Here we describe results from interdisciplinary surveys in the western Nefud that targeted palaeolake deposits identified using satellite imagery. Surveys indicate the presence of thousands of discrete palaeolakes and palaeowetlands, providing valuable palaeoenvironmental records, and numerous archaeological and palaeontological assemblages. Geomorphological investigations suggest that many further deposits remain buried. Forty-six prehistoric archaeological sites have been identified in association with freshwater deposits, spanning the Lower Palaeolithic to the pre-Islamic Holocene. Lower Palaeolithic sites appear concentrated close to raw material sources near the Nefud fringe, despite the presence of freshwater and fauna deeper in the dune field. Middle Palaeolithic occupations extend more broadly, and by the early Holocene humans were at least periodically occupying areas deep in the desert. We present the first records of Neolithic sites in this dune field, including substantial hearth complexes distributed relatively deep within the dunes, potentially indicating increased mobility during this period. Later Holocene sites with stone structures are present around the dune fringes. Our results indicate that, during wet periods of the Pleistocene and Holocene, water in the western Nefud may have been more readily available than elsewhere in northern Arabia due to the high density of depressions where wetlands can form. The high frequency of lakes or marshes appears to have facilitated human occupations and dispersal through the region.

Several hundred Middle Palaeolithic (MP) archaeological sites have now been identified in the Arabian Peninsula. However, the study of lithic raw material properties and related procurement behaviours is still in its infancy. Here we describe raw material procurement and early stage lithic reduction at MP sites in the Jubbah palaeolake basin, in the Nefud Desert, northern Saudi Arabia. We describe the sites identified during our surveys, and we use petrographic studies to demonstrate that MP assemblages were mostly produced from differing forms of ferru-ginous quartzite. These raw materials do not substantially vary in composition, although they are not identical in terms of factors such as grain size and the proportion of iron oxide. We then describe the lithic technology at these sites, with a particular focus on the largest assemblage identified, Jebel Katefeh-12 (JKF-12), which provides detailed information on lithic reduction at a quartzite source. Analyses from this site are then considered together with data from other MP sites in the Jubbah basin, where similar raw material was used. The results indicate that factors such as initial clast size/shape and reduction intensity play important roles in influencing aspects of morphological and technological variability. Our results suggest that incursions of MP populations into northern Arabia were probably temporally limited, as might be expected in a marginal and generally arid region. MP raw material procurement sites provide a highly visible signal of these ephemeral incursions, providing information on the ways that human populations adapted to the challenging conditions of the Saharo-Arabian arid belt.

The evolutionary origins of Homo sapiens and associated behavioural changes are increasingly seen as complex processes, involving multiple regions of Africa. In West Africa, Terminal Pleistocene/Holocene aged human fossils, demonstrating the late continuity of archaic morphological features in the region have been linked to models of surprisingly recent admixture processes between late archaic hominins and H. sapiens. However, the limited chronological resolution of the archaeological record has prevented evaluation of how these biological records relate to patterns of behaviour. Here, we provide a preliminary report of the first excavated and dated Stone Age site in northern Senegal which features the youngest Middle Stone Age (MSA) technology yet documented in Africa. Ndiayène Pendao features classic MSA core axes, basally thinned flakes, Levallois points and denticu-lates mostly made from chert. Similar technological features characterise several, larger surface sites in the vicinity. From this, it is postulated that populations using 'anachronistic' technologies in the Lower Senegal Valley around the transition to the Holocene may have been widespread, in sharp contrast to other areas of Senegal and West Africa. The chronology and technology of Ndiayène Pendao provides the first cultural evidence to support a complex evolutionary history in West Africa. This is consistent with a persistently high degree of Pleisto-cene population substructure in Africa and the spatially and temporally complex character of behavioural and biological evolution.

The current paucity of Pleistocene vertebrate records from the Arabian Peninsula e a landmass of over 3 million km 2 e is a significant gap in our knowledge of the Quaternary. Such data are critical lines of contextual evidence for considering animal and hominin dispersals between Africa and Eurasia generally, and hominin palaeoecology in the Pleistocene landscapes of the Arabian interior specifically. Here, we describe an important contribution to the record and report stratigraphically-constrained fossils of mammals, birds and reptiles from recent excavations at Ti's al Ghadah in the southwestern Nefud Desert. Combined U-series and ESR analyses of Oryx sp. teeth indicate that the assemblage is Middle Pleistocene in age and dates to ca. 500 ka. The identified fauna is a biogeographical admixture that consists of likely endemics and taxa of African and Eurasian affinity and includes extinct and extant (or related Pleistocene forms of) mammals (. alba) and reptiles (Varanidae/Uromastyx sp.). We infer that the assemblage reflects mortality in populations of herbivorous animals and their predators and scavengers that were attracted to freshwater and plant resources in the inter-dune basin. At present, there is no evidence to suggest hominin agency in the accumulation of the bone assemblages. The inferred ecological characteristics of the taxa recovered indicate the presence, at least periodically, of substantial water-bodies and open grassland habitats.

The importance of Africa in human origins is widely recognised, yet knowledge remains strongly biased towards certain regions of the continent at the expense of others. West Africa in particular is a vast area with extremely limited archaeological, environmental and fossil records. In this paper, we contribute towards redressing this imbalance though a summary of the state of knowledge of the West African Middle Stone Age (MSA), and the presentation of preliminary analyses of ten newly discovered MSA archaeological sites situated along the Senegal River. Archaeological, fossil and genetic data relevant to the West African MSA, a period currently thought to span from at least ~150 thousand years ago (ka) until the Terminal Pleistocene, are first discussed.  Technological analyses of newly discovered MSA assemblages in Senegal are then presented and contextualised with the ecology and environmental evolution of West Africa. Our preliminary findings suggest an overall high level of technological diversity along the Senegal River, but identify common technological features between assemblages in northern Senegal. These include an emphasis on centripetal methods of Levallois reduction (both preferential and recurrent). The discovery of tools in northern Senegal with basal modifications consistent with tanging may also suggest some form of connection with North African assemblages and is commensurate with the role of Senegal as a transitional zone between sub-Saharan and Saharan Africa. Although preliminary, the emerging results demonstrate the potential of the region to contribute to debates on intra-African dispersals, including population persistence and turnovers.

Current fossil, genetic, and archeological data indicate that Homo sapiens originated in Africa in the late Middle Pleistocene. By the end of the Late Pleistocene, our species was distributed across every continent except Antarctica, setting the foundations for the subsequent demographic and cultural changes of the Holocene. The intervening processes remain intensely debated and a key theme in hominin evolutionary studies. We review archeological, fossil, environmental, and genetic data to evaluate the current state of knowledge on the dispersal of Homo sapiens out of Africa. The emerging picture of the dispersal process suggests dynamic behavioral variability, complex interactions between populations, and an intricate genetic and cultural legacy. This evolutionary and historical complexity challenges simple narratives and suggests that hybrid models and the testing of explicit hypotheses are required to understand the expansion of Homo sapiens into Eurasia.

Understanding the structure and variation of Homo sapiens populations in Africa is critical for interpreting multiproxy evidence of their subsequent dispersals into Eurasia. However, there is no consensus on early Homo sapiens demographic structure, or its effects on intra-African dispersals. Here, we show how a patchwork of ecological corridors and bottlenecks triggered a successive budding of populations across the Sahara. Using a temporally and spatially explicit palaeoenvironmental model, we found that the Sahara was not uniformly ameliorated between ~130-75 thousand years ago (ka), as has been stated. Model integration with multivariate analyses of corresponding stone tools then revealed several spatially defined technological clusters which correlated with distinct palaeobiomes. Similarities between technological clusters were such that they decreased with distance except where connected by palaeohydrological networks. These results indicate that populations at the Eurasian gateway were strongly structured, which has implications for refining the demographic parameters of dispersals out of Africa.

Quantitative, attribute based analyses of stone tools (lithics) have been frequently used to facilitate large-scale comparative studies, attempt to mitigate problems of assemblage completeness and address interpretations of the co-occurrence of unrelated technological processes. However, a major barrier to the widespread acceptance of such methods has been the lack of quantified experiments that can be externally validated by theoretically distinct approaches in order to guide analysis and confidence in results. Given that quantitative, attribute-based studies now underpin several major interpretations of the archaeological record, the requirement to test the accuracy of such methods has become critical. In this paper, we test the utility of 31 commonly used flake attribute measurements for identifying discrete reduction trajectories through three refitted lithic sets from the Middle Palaeolithic open-air site of Le Pucheuil, in northern France. The experiment had three aims, 1) to determine which, if any, attribute measurements could be used to separate individual refitted sets, and 2) to determine whether variability inherent in the assemblage was primarily driven by different reduction trajectories, as represented by the refitted sets, or other factors, and 3) to determine which multivariate tests were most suitable for these analyses. In order to test the sensitivity of the sample, we ran all analyses twice, the first time with all the available lithics pertaining to each refitted set and the second time with randomly generated 75% sub-samples of each set. All results revealed the consistent accuracy of sixteen attribute measurements in Quadratic and Linear Discriminant Analyses, Principal Components Analyses and Dissimilarity Matrices. These results therefore provide the first quantified attribute formula for comparative lithic analyses of Levallois reduction methods and a basis from which further experiments testing core and retouch attributes may be conducted.

The Empty Quarter (or Rub' al Khali) of the Arabian Peninsula is the largest continuous sandy desert in
the world. It has been known for several decades that Late Pleistocene and Holocene deposits, representing
phases of wetter climate, are preserved there. These sequences have yielded palaeontological
evidence in the form of a variety of vertebrate and invertebrate fossils and have been dated using various
radiometric techniques. However, evidence for human presence during these wetter phases has until
now been ephemeral. Here, we report on the first stratified and dated archaeology from the Empty
Quarter, recovered from the site of Mundafan Al-Buhayrah (MDF-61). Human occupation at the site,
represented by stone tools, has been dated to the later part of Marine Isotope Stage (MIS) 5 using
multiple luminescence dating techniques (multigrain and single grain OSL, TT-OSL). The sequence consists
primarily of lacustrine and palustrine sediments, from which evidence for changing local environmental
conditions has been obtained through analysis of fossil assemblages (phytoliths and nonmarine
molluscs and ostracods). The discovery of securely-dated archaeological material at ~100 to
80 ka in the Empty Quarter has important implications for hypotheses concerning the timing and routes
of dispersal of Homo sapiens out of Africa, which have been much debated. Consequently, the data
presented here fill a crucial gap in palaeoenvironmental and archaeological understanding of the
southern Arabian interior. Fossils of H. sapiens in the Levant, also dated to MIS 5, together with Middle
Palaeolithic archaeological sites in Arabia and India are thought to represent the earliest dispersal of our
species out of Africa. We suggest that the widespread occurrence of similar lithic technologies across
southern Asia, coupled with a growing body of evidence for environmental amelioration across the
Saharo-Arabian belt, indicates that occupation of the Levant by H. sapiens during MIS 5 may not have
been a brief, localized ‘failed dispersal’, but part of a wider demographic expansion.

The dispersal of Homo sapiens out of Africa has been extensively researched across several disciplines. Here we review the evidence for spatial and temporal variability in lithic (stone tool) technologies relative to the predictions of two major hypotheses: 1) that a single successful dispersal occurred 60–50 thousand years ago (ka), marked by a trail of geometric/microlithic technologies, and 2) that multiple dispersals occurred, beginning much earlier (probably in Marine Isotope Stage [MIS] 5), associated with Middle Palaeolithic technology in its early phase. Our results show that Late Pleistocene geometric/microlithic technologies exhibit significant temporal and regional differences between each other. These differences suggest independent, convergent origins for these technologies, which are likely to have been repeatedly re-invented. In contrast, we identify similarities between East African lithic technologies from MIS 8 onwards and Middle Palaeolithic assemblages as far east as India by MIS 5. That this constellation of technological features – particularly an emphasis on centripetal Levallois reduction reflecting interchangeable preferential and recurrent methods, along with particular retouched forms such as points – transcends ecologies and raw material types suggests that it is unlikely to entirely reflect technological convergence (analogy). Our results indicate an early onset of multiple dispersals out of Africa. The hypothesis of an early onset to successful dispersal is entirely consistent with the possibility of further subsequent (post-MIS 5) dispersals out of Africa. Testing such hypotheses through quantified comparative lithic studies and interdisciplinary research is therefore likely to significantly advance understanding of the earliest H. sapiens dispersals.

Freshwater availability is critical for human survival, and in the Saharo-Arabian desert belt repeated fluctuations between aridity and humidity over the Quaternary mean the distribution of freshwater was likely a primary control upon routes and opportunities for hominin dispersals. However, our knowledge of the spatio-temporal distribution of palaeohydrological resources within Arabia during MideLate Pleistocene episodes of climatic amelioration remains limited. In this paper we outline a combined method for remotely mapping the location of palaeodrainage and palaeolakes in currently arid regions that were formerly subject to more humid conditions. We demonstrate the potential of this approach by mapping palaeochannels across the whole Arabian Peninsula, and palaeolakes and marshes for select regions covering c. 10% of its surface. Our palaeodrainage mapping is based upon quantitative thresh- olding of HydroSHEDs data, which applies flow routing to Digital Elevation Model (DEM) data, while our palaeolake mapping uses an innovative method where spectral classification of Landsat Thematic Mapper (TM) imagery is used to detect palaeolake deposits within endorheic (closed) basins, before modelling maximum lake extents by flooding the basin to the level of the elevation of the highest detected deposit. Field survey in the Nefud desert and the Dawadmi and Shuwaymis regions of Saudi Arabia indicates accuracies of 86% for palaeodrainage mapping, and 96% for identifying former palae- olake basins (73% accuracy of classification of individual deposits). The palaeolake mapping method has also demonstrated potential for identifying surface and stratified archaeological site locations, with 76% of the surveyed palaeolake basins containing archaeological material, including stratified Palaeolithic archaeology. Initial examination of palaeodrainage in relation to archaeological sites indicates a relationship between mapped features and previously recorded Palaeolithic sites. An example of the application of these data for period-specific regional palaeohydrological and archaeological re- constructions is presented for a region of Northern Saudi Arabia covering the southern Nefud desert and adjacent lava fields.

The role and significance of the Arabian Peninsula in modern human dispersals out of Africa is currently contentious. While qualitative observations of similarities between Arabian Middle Palaeolithic and African Middle Stone Age (MSA) assemblages have been made, these inferences remain untested and often situated within overly broad dichotomies (e.g. 'Africa' versus the 'Levant') which distort concepts of geographic scale and subsume local variability. Here, we quantitatively test the hypothesis that assemblages from Jubbah, in the Nefud Desert of northern Saudi Arabia are similar to MSA industries from northeast Africa. Based on the quantitative analysis of a suite of metric and morphological data describing lithic reduction sequences, our results show that early and late core reduction at Jubbah is distinct from equivalent northeast African strategies, perhaps as a result of raw material factors. However, specific techniques of core shaping, preparation and preferential flake production at Jubbah draw from a number of methods also present in the northeast African MSA. While two Jubbah lithic assemblages (JKF-1 and JKF-12) display both similarities and differences with the northeast African assemblages, a third locality (JSM-1) was significantly different to both the other Arabian and African assemblages, indicating an unexpected diversity of assemblages in the Jubbah basin during Marine Isotope Stage 5 (MIS 5, ~125-70,000 years ago, or ka). Along with evidence from southern Arabia and the Levant, our results add quantitative support to arguments that MIS 5 hominin demography at the interface between Africa and Asia was complex.

Recent archaeological discoveries indicate that the Arabian Peninsula played an important role in Late Pleistocene hominin dispersals. The presence of Middle Palaeolithic archaeological sites in the Nefud Desert of northern Saudi Arabia demonstrates that hominins moved far inland, probably following networks of ancient lakes and rivers deep into the Arabian interior. These Middle Palaeolithic sites, located close to the spatial and temporal boundary between Neanderthals and Homo sapiens, are critical for our understanding of Late Pleistocene demographic processes and hominin behaviour. Here we present the first detailed analysis of a Middle Palaeolithic lithic assemblage from the north Arabian desert interior. The Late Pleistocene site of Jebel Katefeh-1 (JKF-1) is located beside a palaeolake at Jubbah in the Nefud Desert. The assemblage appears to reflect a relatively short-lived occupation. Reduction produced Levallois flakes of diverse morphologies as well as more expedient small flakes. Our results emphasise that factors such as differential reduction intensity and raw material characteristics need to be considered along with putatively cultural interpretations of Middle Palaeolithic variability. Consideration of assemblage affinities indicates similarities with both the African and Levantine Middle Palaeolithic, perhaps reflecting the location of Jubbah at a crossroads of the highlands of western Arabia, the Levant and the Euphrates/Tigris river system. JKF-1 demonstrates both the potential and the complexity of the Arabian Middle Palaeolithic record in debates on hominin dispersal and adaptation.

The reconstruction of Pleistocene faunas and environments of the Arabian Peninsula is critical to understanding faunal exchange and dispersal between Africa and Eurasia. However, the documented Quaternary vertebrate record of the Peninsula is currently sparse and poorly understood. Small collections have provided a rare insight into the Pleistocene vertebrate communities of northern Arabia, but the chronostratigraphic context of these collections is not clear. Resolving the taxonomic and chronostratigraphic affinities of this fauna is critical to emerging Quaternary frameworks. Here, we summarise recent investigations of the fossiliferous locality of Ti's al Ghadah in the south-western Nefud. Excavations yielded well-preserved fossil bones in a secure stratigraphic context, establishing the potential of this site to make a significant contribution to our understanding of vertebrate diversity and biogeography in the Pleistocene of Arabia. We describe the site and report our pre-liminary observations of newly-recovered stratied vertebrate remains, at present dated to the MiddlePleistocene, which include oryx (Oryx sp.), fox (Vulpes sp.), and notably stratified remains of the Elephantidae and a grebe (Tachybaptus sp.). Here, we give special attention to post-cranial evidence that confirms the presence of a jaguar-sized pantherine, which we refer to the Eurasian jaguar (Panthera cf. gombaszogensis). The occurrence of this taxon during the Middle Pleistocene has important implications for existing biostratigraphical and biogeographical models and for palaeoecological reconstructions of the southern Nefud at that time.

The Nefud Desert is crucial for resolving debates concerning hominin demography and behaviour in the Saharo-Arabian belt. Situated at the interface between the Mediterranean Westerlies and African Monsoonal climate systems, the Nefud lies at the centre of the arid zone crossed by Homo sapiens dispersing into Eurasia and the edges of the southernmost known extent of the Neanderthal range. In 2013, the Palaeodeserts Project conducted an intensive survey of the western Nefud, to: (1) evaluate Pleistocene population dynamics in this important region of the Saharo-Arabian belt and (2) contribute towards understanding early modern human range expansions and interactions between different hominin species. Thirteen Lower and Middle Palaeolithic sites were discovered in association with palaeolake basins. One of the sites, T'is al Ghadah, may feature the earliest Middle Palaeolithic assemblage of Arabia. Preliminary analyses show that the Lower and Middle Palaeolithic sites discovered display diverse technological characteristics, indicating that the Nefud was important for population turnovers and exchanges throughout the Pleistocene. Periodic environmental amelioration appears to have attracted hominin incursions into the region, and subsequent ephemeral occupations structured around lakes and, to a lesser extent, raw material sources. However, differences between the Lower and Middle Palaeolithic sites are indicative of greater mobility during the later Pleistocene. A rarity of formal tools, but strong similarities in lithic production techniques, are also suggestive of demographic affinities across the Nefud during the Pleistocene, and perhaps beyond. These preliminary results support the view that the Arabian Peninsula was a critically important region of southwest Asia during the Late Pleistocene, in which demographic responses to climatic amelioration may have structured connectivity across the Saharo-Arabian belt, the Levant and as far as India.